2.4: Crito By Plato (Translated by Benjamin Jowett)
Introduction
The Crito seems intended to exhibit the character of Socrates in one light only, not as the philosopher, fulfilling a divine mission and trusting in the will of heaven, but simply as the good citizen, who having been unjustly condemned is willing to give up his life in obedience to the laws of the state . . .
The days of Socrates are drawing to a close; the fatal ship has been seen off Sunium, as he is informed by his aged friend and contemporary Crito, who visits him before the dawn has broken; he himself has been warned in a dream that on the third day he must depart. Time is precious, and Crito has come early in order to gain his consent to a plan of escape. This can be easily accomplished by his friends, who will incur no danger in making the attempt to save him, but will be disgraced for ever if they allow him to perish. He should think of his duty to his children, and not play into the hands of his enemies. Money is already provided by Crito as well as by Simmias and others, and he will have no difficulty in finding friends in Thessaly and other places.
Socrates is afraid that Crito is but pressing upon him the opinions of the many; whereas, all his life long he has followed the dictates of reason only and the opinion of the one wise or skilled man. There was a time when Crito himself had allowed the propriety of this.  All considerations of loss of reputation or injury to his children should be dismissed: the only question is whether he would be right in attempting to escape. Crito, who is a disinterested person not having the fear of death before his eyes, shall answer this for him. Before he was condemned they had often held discussions, in which they agreed that no man should either do evil, or return evil for evil, or betray the right. Are these principles to be altered because the circumstances of Socrates are altered? Crito admits that they remain the same. Then is his escape consistent with the maintenance of them? To this Crito is unable or unwilling to reply.
Socrates proceeds:—Suppose the Laws of Athens to come and remonstrate with him: they will ask, ‘Why does he seek to overturn them?’ and if he replies, ‘They have injured him,’ will not the Laws answer, ‘Yes, but was that the agreement? Has he any objection to make to them which would justify him in overturning them?  He might have left Athens and gone where he pleased, but he has lived there for seventy years more constantly than any other citizen.’ Thus he has clearly shown that he acknowledged the agreement, which he cannot now break without dishonour to himself and danger to his friends. Even in the course of the trial he might have proposed exile as the penalty, but then he declared that he preferred death to exile. And whither will he direct his footsteps? In any well-ordered state the Laws will consider him as an enemy. Possibly in a land of misrule like Thessaly he may be welcomed at first, and the unseemly narrative of his escape will be regarded by the inhabitants as an amusing tale. But if he offends them he will have to learn another sort of lesson. Will he continue to give lectures in virtue? That would hardly be decent. And how will his children be the gainers if he takes them into Thessaly, and deprives them of Athenian citizenship? Or if he leaves them behind, does he expect that they will be better taken care of by his friends because he is in Thessaly? Will not true friends care for them equally whether he is alive or dead?
Finally, they exhort him to think of justice first, and of life and children afterwards. He may now depart in peace and innocence, a sufferer and not a doer of evil. But if he breaks agreements, and returns evil for evil, they will be angry with him while he lives; and their brethren the Laws of the world below will receive him as an enemy. Such is the mystic voice which is always murmuring in his ears.
That Socrates was not a good citizen was a charge made against him during his lifetime, which has been often repeated in later ages. The crimes of Alcibiades, Critias, and Charmides, who had been his pupils, were still recent in the memory of the now restored democracy. The fact that he had been neutral in the death-struggle of Athens was not likely to conciliate popular good-will. Plato, writing probably in the next generation, undertakes the defence of his friend and master in this particular, not to the Athenians of his day, but to posterity and the world at large.
Whether such an incident ever really occurred as the visit of Crito and the proposal of escape is uncertain; Plato could easily have invented far more than that; 1 and in the selection of Crito, the aged friend, as the fittest person to make the proposal to Socrates, we seem to recognize the hand of the artist. Whether anyone who has been subjected by the laws of his country to an unjust judgment is right in attempting to escape, is a thesis about which casuists might disagree. Shelley 2 is of opinion that Socrates ‘did well to die,’ but not for the ‘sophistical’ reasons which Plato has put into his mouth. And there would be no difficulty in arguing that Socrates should have lived and preferred to a glorious death the good which he might still be able to perform. ‘A rhetorician would have had much to say upon that point.’ It may be observed however that Plato never intended to answer the question of casuistry, but only to exhibit the ideal of patient virtue which refuses to do the least evil in order to avoid the greatest, and to show his master maintaining in death the opinions which he had professed in his life. Not ‘the world,’ but the ‘one wise man,’ is still the paradox of Socrates in his last hours. He must be guided by reason, although her conclusions may be fatal to him. The remarkable sentiment that the wicked can do neither good nor evil is true, if taken in the sense, which he means, of moral evil; in his own words, ‘they cannot make a man wise or foolish.’
This little dialogue is a perfect piece of dialectic, in which granting the ‘common principle,’ there is no escaping from the conclusion. It is anticipated at the beginning by the dream of Socrates and the parody of Homer. The personification of the Laws, and of their brethren the Laws in the world below, is one of the noblest and boldest figures of speech which occur in Plato.
Crito
PERSONS OF THE DIALOGUE: Socrates, Crito.
SCENE: The Prison of Socrates.
SOCRATES: Why have you come at this hour, Crito? it must be quite early?
CRITO: Yes, certainly.
SOCRATES: What is the exact time?
CRITO: The dawn is breaking.
SOCRATES: I wonder that the keeper of the prison would let you in.
CRITO: He knows me, because I often come, Socrates; moreover, I have done him a kindness.
SOCRATES: And are you only just arrived?
CRITO: No, I came some time ago.
SOCRATES: Then why did you sit and say nothing, instead of at once awakening me?
CRITO: I should not have liked myself, Socrates, to be in such great trouble and unrest as you are—indeed I should not: I have been watching with amazement your peaceful slumbers; and for that reason I did not awake you, because I wished to minimize the pain. I have always thought you to be of a happy disposition; but never did I see anything like the easy, tranquil manner in which you bear this calamity.
SOCRATES: Why, Crito, when a man has reached my age he ought not to be repining at the approach of death.
CRITO: And yet other old men find themselves in similar misfortunes, and age does not prevent them from repining.
SOCRATES: That is true. But you have not told me why you come at this early hour.
CRITO: I come to bring you a message which is sad and painful; not, as I believe, to yourself, but to all of us who are your friends, and saddest of all to me.
SOCRATES: What? Has the ship come from Delos, on the arrival of which I am to die?
CRITO: No, the ship has not actually arrived, but she will probably be here to-day, as persons who have come from Sunium tell me that they have left her there; and therefore to-morrow, Socrates, will be the last day of your life.
SOCRATES: Very well, Crito; if such is the will of God, I am willing; but my belief is that there will be a delay of a day.
CRITO: Why do you think so?
SOCRATES: I will tell you. I am to die on the day after the arrival of the ship?
CRITO: Yes; that is what the authorities say.
SOCRATES: But I do not think that the ship will be here until to-morrow; this I infer from a vision which I had last night, or rather only just now, when you fortunately allowed me to sleep.
CRITO: And what was the nature of the vision?
SOCRATES: There appeared to me the likeness of a woman, fair and comely, clothed in bright raiment, who called to me and said: O Socrates, ‘The third day hence to fertile Phthia shalt thou go.’ 3
CRITO: What a singular dream, Socrates!
SOCRATES: There can be no doubt about the meaning, Crito, I think.
CRITO: Yes; the meaning is only too clear. But, oh! my beloved Socrates, let me entreat you once more to take my advice and escape. For if you die I shall not only lose a friend who can never be replaced, but there is another evil: people who do not know you and me will believe that I might have saved you if I had been willing to give money, but that I did not care. Now, can there be a worse disgrace than this—that I should be thought to value money more than the life of a friend? For the many will not be persuaded that I wanted you to escape, and that you refused.
SOCRATES: But why, my dear Crito, should we care about the opinion of the many? Good men, and they are the only persons who are worth considering, will think of these things truly as they occurred.
CRITO: But you see, Socrates, that the opinion of the many must be regarded, for what is now happening shows that they can do the greatest evil to anyone who has lost their good opinion.
SOCRATES: I only wish it were so, Crito; and that the many could do the greatest evil; for then they would also be able to do the greatest good—and what a fine thing this would be! But in reality they can do neither; for they cannot make a man either wise or foolish; and whatever they do is the result of chance.
CRITO: Well, I will not dispute with you; but please to tell me, Socrates, whether you are not acting out of regard to me and your other friends: are you not afraid that if you escape from prison we may get into trouble with the informers for having stolen you away, and lose either the whole or a great part of our property; or that even a worse evil may happen to us? Now, if you fear on our account, be at ease; for in order to save you, we ought surely to run this, or even a greater risk; be persuaded, then, and do as I say.
SOCRATES: Yes, Crito, that is one fear which you mention, but by no means the only one.
CRITO: Fear not—there are persons who are willing to get you out of prison at no great cost; and as for the informers, they are far from being exorbitant in their demands—a little money will satisfy them. My means, which are certainly ample, are at your service, and if you have a scruple about spending all mine, here are strangers who will give you the use of theirs; and one of them, Simmias the Theban, has brought a large sum of money for this very purpose; and Cebes and many others are prepared to spend their money in helping you to escape. I say, therefore, do not hesitate on our account, and do not say, as you did in the court 4 that you will have a difficulty in knowing what to do with yourself anywhere else. For men will love you in other places to which you may go, and not in Athens only; there are friends of mine in Thessaly, if you like to go to them, who will value and protect you, and no Thessalian will give you any trouble. Nor can I think that you are at all justified, Socrates, in betraying your own life when you might be saved; in acting thus you are playing into the hands of your enemies, who are hurrying on your destruction. And further I should say that you are deserting your own children; for you might bring them up and educate them; instead of which you go away and leave them, and they will have to take their chance; and if they do not meet with the usual fate of orphans, there will be small thanks to you. No man should bring children into the world who is unwilling to persevere to the end in their nurture and education. But you appear to be choosing the easier part, not the better and manlier, which would have been more becoming in one who professes to care for virtue in all his actions, like yourself. And indeed, I am ashamed not only of you, but of us who are your friends, when I reflect that the whole business will be attributed entirely to our want of courage. The trial need never have come on, or might have been managed differently; and this last act, or crowning folly, will seem to have occurred through our negligence and cowardice, who might have saved you, if we had been good for anything; and you might have saved yourself, for there was no difficulty at all. See now, Socrates, how sad and discreditable are the consequences, both to us and you. Make up your mind then, or rather have your mind already made up, for the time of deliberation is over, and there is only one thing to be done, which must be done this very night, and, if we delay at all, will be no longer practicable or possible; I beseech you therefore, Socrates, be persuaded by me, and do as I say.
SOCRATES: Dear Crito, your zeal is invaluable, if a right one; but if wrong, the greater the zeal the greater the danger; and therefore we ought to consider whether I shall or shall not do as you say. For I am and always have been one of those natures who must be guided by reason, whatever the reason may be which upon reflection appears to me to be the best; and now that this chance has befallen me, I cannot repudiate my own words: the principles which I have hitherto honoured and revered I still honour, and unless we can at once find other and better principles, I am certain not to agree with you; no, not even if the power of the multitude could inflict many more imprisonments, confiscations, deaths, frightening us like children with hobgoblin terrors. 5 What will be the fairest way of considering the question? Shall I return to your old argument about the opinions of men?—we were saying that some of them are to be regarded, and others not. Now were we right in maintaining this before I was condemned? And has the argument which was once good now proved to be talk for the sake of talking—mere childish nonsense? That is what I want to consider with your help, Crito:—whether, under my present circumstances, the argument appears to be in any way different or not; and is to be allowed by me or disallowed. That argument, which, as I believe, is maintained by many persons of authority, was to the effect, as I was saying, that the opinions of some men are to be regarded, and of other men not to be regarded.  Tell me then, whether I am right in saying that some opinions, and the opinions of some men only, are to be valued, and that other opinions, and the opinions of other men, are not to be valued. I ask you whether I was right in maintaining this?
CRITO: Certainly.
SOCRATES: The good are to be regarded, and not the bad?
CRITO: Yes.
SOCRATES: And the opinions of the wise are good, and the opinions of the unwise are evil?
CRITO: Certainly.
SOCRATES: And what was said about another matter? Is the pupil who devotes himself to the practice of gymnastics supposed to attend to the praise and blame and opinion of every man, or of one man only—his physician or trainer, whoever he may be?
CRITO: Of one man only.
SOCRATES: And he ought to fear the censure and welcome the praise of that one only, and not of the many?
CRITO: Clearly so.
SOCRATES: And he ought to act and train, and eat and drink in the way which seems good to his single master who has understanding, rather than according to the opinion of all other men put together?
CRITO: True.
SOCRATES: And if he disobeys and disregards the opinion and approval of the one, and regards the opinion of the many who have no understanding, will he not suffer evil?
CRITO: Certainly he will.
SOCRATES: And what will the evil be, whither tending and what affecting, in the disobedient person?
CRITO: Clearly, affecting the body; that is what is destroyed by the evil.
SOCRATES: Very good; and is not this true, Crito, of other things which we need not separately enumerate? In questions of just and unjust, fair and foul, good and evil, which are the subjects of our present consultation, ought we to follow the opinion of the many and to fear them; or the opinion of the one man who has understanding? ought we not to fear and reverence him more than all the rest of the world: and if we desert him shall we not destroy and injure that principle in us which may be assumed to be improved by justice and deteriorated by injustice—there is such a principle?
CRITO: Certainly there is, Socrates.
SOCRATES: Take a parallel instance:—if, acting under the advice of those who have no understanding, we destroy that which is improved by health and is deteriorated by disease, would life be worth having? And that which has been destroyed is—the body?
CRITO: Yes.

CRITO: Certainly not.
SOCRATES: And will life be worth having, if that higher part of man be destroyed, which is improved by justice and depraved by injustice? Do we suppose that principle, whatever it may be in man, which has to do with justice and injustice, to be inferior to the body?
CRITO: Certainly not.
SOCRATES: More honourable than the body?
CRITO: Far more.
SOCRATES: Then, my friend, we must not regard what the many say of us; but what he, the one man who has understanding of just and unjust, will say, and what the truth will say. And therefore you begin in error when you advise that we should regard the opinion of the many about just and unjust, good and evil, honourable and dishonourable.—‘Well,’ someone will say, ‘but the many can kill us.’
CRITO: Yes, Socrates; that will clearly be the answer.
SOCRATES: And it is true; but still I find with surprise that the old argument is unshaken as ever. And I should like to know whether I may say the same of another proposition—that not life, but a good life, is to be chiefly valued?
CRITO: Yes, that also remains unshaken.
SOCRATES: And a good life is equivalent to a just and honourable one—that holds also?
CRITO: Yes, it does.
SOCRATES: From these premises I proceed to argue the question whether I ought or ought not to try and escape without the consent of the Athenians: and if I am clearly right in escaping, then I will make the attempt; but if not, I will abstain. The other considerations which you mention, of money and loss of character and the duty of educating one’s children, are, I fear, only the doctrines of the multitude, who would be as ready to restore people to life, if they were able, as they are to put them to death—and with as little reason. But now, since the argument has thus far prevailed, the only question which remains to be considered is whether we shall do rightly either in escaping or in suffering others to aid in our escape and paying them in money and thanks, or whether in reality we shall not do rightly; and if the latter, then death or any other calamity which may ensue on my remaining here must not be allowed to enter into the calculation.
CRITO: I think that you are right, Socrates; how then shall we proceed?
SOCRATES: Let us consider the matter together, and do you either refute me if you can, and I will be convinced; or else cease, my dear friend, from repeating to me that I ought to escape against the wishes of the Athenians: for I highly value your attempts to persuade me to do so, but I may not be persuaded against my own better judgment. And now please to consider my first position, and try how you can best answer me.
CRITO: I will.
SOCRATES: Are we to say that we are never intentionally to do wrong, or that in one way we ought and in another way we ought not to do wrong, or is doing wrong always evil and dishonourable, as I was just now saying, and as has been already acknowledged by us? Are all our former admissions which were made within a few days to be thrown away? And have we, at our age, been earnestly discoursing with one another all our life long only to discover that we are no better than children? Or, in spite of the opinion of the many, and in spite of consequences whether better or worse, shall we insist on the truth of what was then said, that injustice is always an evil and dishonour to him who acts unjustly? Shall we say so or not?
CRITO: Yes.
SOCRATES: Then we must do no wrong?
CRITO: Certainly not.
SOCRATES: Nor, when injured, injure in return, as the many imagine; for we must injure no one at all? 6
CRITO: Clearly not.
SOCRATES: Again, Crito, may we do evil?
CRITO: Surely not, Socrates.
SOCRATES: And what of doing evil in return for evil, which is the morality of the many—is that just or not?
CRITO: Not just.
SOCRATES: For doing evil to another is the same as injuring him?
CRITO: Very true.
SOCRATES: Then we ought not to retaliate or render evil for evil to anyone, whatever evil we may have suffered from him. But I would have you consider, Crito, whether you really mean what you are saying. For this opinion has never been held, and never will be held, by any considerable number of persons; and those who are agreed and those who are not agreed upon this point have no common ground, and can only despise one another when they see how widely they differ. Tell me, then, whether you agree with and assent to my first principle, that neither injury nor retaliation nor warding off evil by evil is ever right. And shall that be the premise of our argument? Or do you decline and dissent from this? For so I have ever thought, and continue to think; but, if you are of another opinion, let me hear what you have to say. If, however, you remain of the same mind as formerly, I will proceed to the next step.
CRITO: You may proceed, for I have not changed my mind.
SOCRATES: Then I will go on to the next point, which may be put in the form of a question:—Ought a man to do what he admits to be right, or ought he to betray the right?
CRITO: He ought to do what he thinks right.
SOCRATES: But if this is true, what is the application? In leaving the prison against the will of the Athenians, do I wrong any? or rather do I not wrong those whom I ought least to wrong? Do I not desert the principles which were acknowledged by us to be just—what do you say?
CRITO: I cannot tell, Socrates; for I do not know.
 Do you imagine that a state can subsist and not be overthrown, in which the decisions of law have no power, but are set aside and trampled upon by individuals?’ What will be our answer, Crito, to these and the like words? Anyone, and especially a rhetorician, will have a good deal to say on behalf of the law which requires a sentence to be carried out. He will argue that this law should not be set aside; and shall we reply, ‘Yes; but the state has injured us and given an unjust sentence.’ Suppose I say that?
CRITO: Very good, Socrates.
SOCRATES: ‘And was that our agreement with you?’ the law would answer; ‘or were you to abide by the sentence of the state?’ And if I were to express my astonishment at their words, the law would probably add: ‘Answer, Socrates, instead of opening your eyes—you are in the habit of asking and answering questions. Tell us,—What complaint have you to make against us which justifies you in attempting to destroy us and the state? In the first place did we not bring you into existence?  Say whether you have any objection to urge against those of us who regulate marriage?’ None, I should reply. ‘Or against those of us who after birth regulate the nurture and education of children, in which you also were trained? Were not the laws, which have the charge of education, right in commanding your father to train you in music and gymnastic?’ Right, I should reply. ‘Well then, since you were brought into the world and nurtured and educated by us, can you deny in the first place that you are our child and slave, as your fathers were before you? And if this is true you are not on equal terms with us; nor can you think that you have a right to do to us what we are doing to you. Would you have any right to strike or revile or do any other evil to your father or your master, if you had one, because you have been struck or reviled by him, or received some other evil at his hands? You would not say this.  Will you, O professor of true virtue, pretend that you are justified in this? Has a philosopher like you failed to discover that our country is more to be valued and higher and holier far than mother or father or any ancestor, and more to be regarded in the eyes of the gods and of men of understanding? also to be soothed, and gently and reverently entreated when angry, even more than a father, and either to be persuaded, or if not persuaded, to be obeyed? And when we are punished by her, whether with imprisonment or stripes, the punishment is to be endured in silence; and if she lead us to wounds or death in battle, thither we follow as is right; neither may anyone yield or retreat or leave his rank, but whether in battle or in a court of law, or in any other place, he must do what his city and his country order him; or he must change their view of what is just: and if he may do no violence to his father or mother, much less may he do violence to his country.’ What answer shall we make to this, Crito? Do the laws speak truly, or do they not?
CRITO: I think that they do.
SOCRATES: Then the laws will say: ‘Consider, Socrates, if we are speaking truly that in your present attempt you are going to do us an injury. For, having brought you into the world, and nurtured and educated you, and given you and every other citizen a share in every good which we had to give, we further proclaim to any Athenian by the liberty which we allow him, that if he does not like us when he has become of age and has seen the ways of the city, and made our acquaintance, he may go where he pleases and take his goods with him. None of us laws will forbid him or interfere with him. Anyone who does not like us and the city, and who wants to emigrate to a colony or to any other city, may go where he likes, retaining his property. But he who has experience of the manner in which we order justice and administer the state, and still remains, has entered into an implied contract that he will do as we command him. And he who disobeys us is, as we maintain, thrice wrong; first, because in disobeying us he is disobeying his parents; secondly, because we are the authors of his education; thirdly, because he has made an agreement with us that he will duly obey our commands; and he neither obeys them nor convinces us that our commands are unjust; and we do not rudely impose them, but give him the alternative of obeying or convincing us;—that is what we offer, and he does neither.
Suppose now I ask, why I rather than anybody else? they will justly retort upon me that I above all other men have acknowledged the agreement. ‘There is clear proof,’ they will say, ‘Socrates, that we and the city were not displeasing to you. Of all Athenians you have been the most constant resident in the city, which, as you never leave, you may be supposed to love. 7 For you never went out of the city either to see the games, except once when you went to the Isthmus, or to any other place unless when you were on military service; nor did you travel as other men do. Nor had you any curiosity to know other states or their laws: your affections did not go beyond us and our state; we were your especial favourites, and you acquiesced in our government of you; and here in this city you begat your children, which is a proof of your satisfaction. Moreover, you might in the course of the trial, if you had liked, have fixed the penalty at banishment; the state which refuses to let you go now would have let you go then.  And now you have forgotten these fine sentiments, and pay no respect to us the laws, of whom you are the destroyer; and are doing what only a miserable slave would do, running away and turning your back upon the compacts and agreements which you made as a citizen. And first of all answer this very question: Are we right in saying that you agreed to be governed according to us in deed, and not in word only? Is that true or not?’ How shall we answer, Crito? Must we not assent?
CRITO: We cannot help it, Socrates.
SOCRATES: Then will they not say: ‘You, Socrates, are breaking the covenants and agreements which you made with us at your leisure, not in any haste or under any compulsion or deception, but after you have had seventy years to think of them, during which time you were at liberty to leave the city, if we were not to your mind, or if our covenants appeared to you to be unfair. You had your choice, and might have gone either to Lacedaemon or Crete, both which states are often praised by you for their good government, or to some other Hellenic or foreign state. Whereas you, above all other Athenians, seemed to be so fond of the state, or, in other words, of us, her laws (and who would care about a state which has no laws?), that you never stirred out of her; the halt, the blind, the maimed were not more stationary in her than you were.  Not so, Socrates, if you will take our advice; do not make yourself ridiculous by escaping out of the city.
‘For just consider, if you transgress and err in this sort of way, what good will you do either to yourself or to your friends? That your friends will be driven into exile and deprived of citizenship, or will lose their property, is tolerably certain; and you yourself, if you fly to one of the neighbouring cities, as, for example, Thebes or Megara, both of which are well governed, will come to them as an enemy, Socrates, and their government will be against you, and all patriotic citizens will cast an evil eye upon you as a subverter of the laws, and you will confirm in the minds of the judges the justice of their own condemnation of you. For he who is a corrupter of the laws is more than likely to be a corrupter of the young and foolish portion of mankind. Will you then flee from well-ordered cities and virtuous men? and is existence worth having on these terms? Or will you go to them without shame, and talk to them, Socrates? And what will you say to them? What you say here about virtue and justice and institutions and laws being the best things among men? Would that be decent of you? Surely not. But if you go away from well-governed states to Crito’s friends in Thessaly, where there is great disorder and licence, they will be charmed to hear the tale of your escape from prison, set off with ludicrous particulars of the manner in which you were wrapped in a goatskin or some other disguise, and metamorphosed as the manner is of runaways; but will there be no one to remind you that in your old age you were not ashamed to violate the most sacred laws from a miserable desire of a little more life? Perhaps not, if you keep them in a good temper; but if they are out of temper you will hear many degrading things; you will live, but how?—as the flatterer of all men, and the servant of all men; and doing what?—eating and drinking in Thessaly, having gone abroad in order that you may get a dinner. And where will be your fine sentiments about justice and virtue? Say that you wish to live for the sake of your children—you want to bring them up and educate them—will you take them into Thessaly and deprive them of Athenian citizenship? Is this the benefit which you will confer upon them? Or are you under the impression that they will be better cared for and educated here if you are still alive, although absent from them; for your friends will take care of them? Do you fancy that if you are an inhabitant of Thessaly they will take care of them, and if you are an inhabitant of the other world that they will not take care of them? Nay; but if they who call themselves friends are good for anything, they will—to be sure they will.
 Think not of life and children first, and of justice afterwards, but of justice first, that you may be justified before the princes of the world below. For neither will you nor any that belong to you be happier or holier or juster in this life, or happier in another, if you do as Crito bids. Now you depart in innocence, a sufferer and not a doer of evil; a victim, not of the laws, but of men. But if you go forth, returning evil for evil, and injury for injury, breaking the covenants and agreements which you have made with us, and wronging those whom you ought least of all to wrong, that is to say, yourself, your friends, your country, and us, we shall be angry with you while you live, and our brethren, the laws in the world below, will receive you as an enemy; for they will know that you have done your best to destroy us. Listen, then, to us and not to Crito.’
This, dear Crito, is the voice which I seem to hear murmuring in my ears, like the sound of the flute in the ears of the mystic; that voice, I say, is humming in my ears, and prevents me from hearing any other. And I know that anything more which you may say will be vain. Yet speak, if you have anything to say.
CRITO: I have nothing to say, Socrates.
SOCRATES: Leave me then, Crito, to fulfil the will of God, and to follow whither he leads.


5: Setting the Stage for Play- Environments
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Learning Objectives
After reading this chapter, students will be able to:
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Identify the role of the Environment as a “Teacher”
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Connect Early Childhood Theories to the Environment
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Understand Learning Areas and Zones for DAP
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Identify and list appropriate materials for each learning area
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Analyze a variety of floor plans for indoors and outdoors
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Explore Temporal Environment by looking at schedules, routines and rituals, and transitions
The environment is often labeled as a “teacher” in Early Childhood Education. The meaning behind this label is that if an environment is intentionally created with developmentally appropriate practice in mind, it will serve to assist with learning as well as classroom management. A quality early childhood educational environment, whether it is indoor, outdoor or temporal, should encourage engagement, stimulate learning and promote growth in all areas of development.
The effective preschool teacher recognizes, understands, and respects the values of children’s families and communities and attempts to make the preschool environment as congruent with those values as possible.
[1]


9.6: Editing a Presentation
Learning Outcomes
- Edit an existing presentation.
To open an existing presentation, simply double-click on the presentation file, just the same as opening a Word document or Excel file that you have already been given.
You may also open a presentation using the Ctrl+O (Cmnd+O) shortcut or through the File menu if you already have a presentation open.
Once you have opened an existing presentation, one of the first steps you may want to take is to edit content within that presentation. However, before we begin that step let us look at the default view when we have opened a presentation, and review a few terms.
- Slide thumbnail view : this shows you smaller images of all the slides in a presentation. It has its own scroll bar if there are more slides than will fit in a single viewing window.
- Active slide thumbnail : the active slide is highlighted in an orange box in the thumbnail view.
- Active slide : this is the main view of the active slide you are currently viewing and can edit. You can see the scroll bar on the right that allows you to move quickly through the presentation.
You can move between slides in a presentation using either the slide thumbnail view of the slides or in the main window. The slide shown in the main window is the active slide for editing.
In order to edit what a slide displays, click on the text or image you wish to edit. For example, the slide shown above says “Quarterly Sales Data.” In the image below, the text box containing that phrase has been selected. The green arrow is pointing into the active text box, specifically at the location of the cursor.
In the next screenshot, “Quarterly” has been edited to read “Monthly.”
Contributors and Attributions
- Editing a Presentation. Authored by : Shelli Carter. Provided by : Lumen Learning. License : CC BY: Attribution


2.4A: Organic Molecules and Functional Groups
Functional groups are groups of molecules attached to organic molecules and give them specific identities or functions.
- Describe the importance of functional groups to organic molecules
Key Points
- Functional groups are collections of atoms that attach the carbon skeleton of an organic molecule and confer specific properties.
- Each type of organic molecule has its own specific type of functional group.
- Functional groups in biological molecules play an important role in the formation of molecules like DNA, proteins, carbohydrates, and lipids.
- Functional groups include: hydroxyl, methyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl.
Key Terms
- hydrophobic : lacking an affinity for water; unable to absorb, or be wetted by water
- hydrophilic : having an affinity for water; able to absorb, or be wetted by water
Location of Functional Groups
Functional groups are groups of atoms that occur within organic molecules and confer specific chemical properties to those molecules. When functional groups are shown, the organic molecule is sometimes denoted as “R.” Functional groups are found along the “carbon backbone” of macromolecules which is formed by chains and/or rings of carbon atoms with the occasional substitution of an element such as nitrogen or oxygen. Molecules with other elements in their carbon backbone are substituted hydrocarbons. Each of the four types of macromolecules—proteins, lipids, carbohydrates, and nucleic acids—has its own characteristic set of functional groups that contributes greatly to its differing chemical properties and its function in living organisms.
Properties of Functional Groups
A functional group can participate in specific chemical reactions. Some of the important functional groups in biological molecules include: hydroxyl, methyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl groups. These groups play an important role in the formation of molecules like DNA, proteins, carbohydrates, and lipids.
Classifying Functional Groups
Functional groups are usually classified as hydrophobic or hydrophilic depending on their charge or polarity. An example of a hydrophobic group is the non-polar methane molecule. Among the hydrophilic functional groups is the carboxyl group found in amino acids, some amino acid side chains, and the fatty acid heads that form triglycerides and phospholipids. This carboxyl group ionizes to release hydrogen ions (H + ) from the COOH group resulting in the negatively charged COO − group; this contributes to the hydrophilic nature of whatever molecule it is found on. Other functional groups, such as the carbonyl group, have a partially negatively charged oxygen atom that may form hydrogen bonds with water molecules, again making the molecule more hydrophilic. The functional groups shown here are found in many different biological molecules, where “R” is the organic molecule.
| Important Functional Groups in Biology | ||
|---|---|---|
| Functional Group | Structure | Properties |
| Hydroxyl | Polar | |
| Methyl | Nonpolar | |
| Carbonyl | Polar | |
| Carboxyl | Charged, ionized to release H + . Since carboxyl groups can release H + ions into a solution, they are considered acidic. | |
| Amino | Charged, accepts H + to form NH 3 + . Since amino groups can remove H + from solution, they are considered basic. | |
| Phosphate | Charged, ionizes to release H + . Since phosphate groups can release H + ions into solution, they are considered acidic. | |
| Sulfhydryl | Polar |
Hydrogen Bonds between Functional Groups
Hydrogen bonds between functional groups (within the same molecule or between different molecules) are important to the function of many macromolecules and help them to fold properly and maintain the appropriate shape needed to function correctly. Hydrogen bonds are also involved in various recognition processes, such as DNA complementary base pairing and the binding of an enzyme to its substrate.
Hydrogen bonds in DNA : Hydrogen bonds connect two strands of DNA together to create the double-helix structure.


5.9: Reading- A Culture of Accountability
At the beginning of this module we discussed the 2015 revelation that Volkswagen installed emissions-altering software in eleven million diesel vehicles worldwide, which caused the cars to pass emissions tests they should have failed. Consider, for a moment, how many employees would have to be involved in order to achieve this level of fraud? This was not the handiwork of a single employee but the result of a pattern of unethical behavior in the company. When the Ethics & Compliance Initiative (ECI) released the results of its 2013 National Business Ethics Survey, it noted that these types of broad, organizational breaches are fairly common.
The survey shows that a significant amount of misconduct involves continuous, ongoing behavior rather than one-time incidents: Employees say that more than a quarter (26 percent) of observed misconduct represents an ongoing pattern of behavior. Another 41 percent said the behavior has been repeated at least a second time. Only one-third (33 percent) of rule breaking represents a one-time incident. [1]
In the case of Volkswagen, an early internal investigation pointed to a “culture of tolerance” for ethical compromises. Employees were pushed to do what was needed to meet corporate objectives at any cost.
The organizational culture is comprised of the values and beliefs that an organization shares, which create its social environment. The culture of a large organization can be difficult to understand since it is influenced by many different factors. Still, many research studies point to leadership and policies as being instrumental in building an ethical organizational culture.
Policies That Encourage Ethical Behavior
Many companies have a specific policy that defines appropriate behavior. The policy is often called the Standards for Business Conduct. As the name suggests, the policy is intended to set the standards for acceptable behavior; it’s not meant to be an exhaustive list of every type of ethical behavior.
Many of these policies do the following:
- Define the threshold for behavior: While it should go without saying that employees are expected to be law abiding, companies choose to be quite explicit about stating that they require their employees to follow the law.
- Create expectations for behavior: The policies identify common issues that employees may encounter—such as accepting gifts from suppliers—and explain how they should be handled.
- Set policy: establish company protocols for handling confidential information, including customer data, etc.
- Give guidance on making judgment calls: Companies often define how they would like employees to make decisions when guidelines do not adequately cover them.
- Describe reporting and enforcement procedures: There is generally a process for reporting and addressing issues, as well as information about how the company will protect those reporting concerns.
Let’s examine some examples from company policies to see how some of these components are addressed.
The Legal Threshold
The ethics policy generally begins by reminding employees that they are required to act in accordance with the law. For companies that engage in business across the globe this can be complex. Starwood Hotels and Resorts addresses this issue in their Code of Business Conduct and Ethics:
You must, at all times, obey the laws of the jurisdictions where we conduct business. Starwood conducts business all around the world. Our associates are citizens of many countries. As a result, our operations are subject to the laws of many jurisdictions. It is often challenging for us to understand how those various laws apply to our businesses. However, whether you are a Starwood associate or member of the Board of Directors, you are expected to conduct yourself in accordance with applicable law.
Starwood is a company organized under the laws of the United States and is generally subject to U.S. federal law. From time to time, the laws of the United States conflict with laws of a city, town, country or other jurisdiction where we conduct business. If there is a conflict between the applicable laws, seek guidance from the Office of the General Counsel (Legal). [2]
Starwood has established a clear expectation to follow the law, acknowledged the complexity of their business environment, and provided direction when employees need help.
Creating Expectations for Behavior
In the course of a normal business day, many service employees receive tips. Where is the line between an appropriate tip and a gift? Starbucks has defined this for employees in its Standards of Business Conduct:
A gift or favor should not be accepted or given if it might create a sense of obligation, compromise your professional judgment or create the appearance of doing so. In deciding whether a gift is appropriate, you should consider its value and whether public disclosure of the gift would embarrass you or Starbucks.
A gift of money should never be given or accepted. (Some retail partners, however, may accept customary tips for service well done.) As a general rule, partners should limit gifts to or from any one vendor or business associate to US $75 per year. A gift of nominal value may be given or accepted if it is a common business courtesy, such as coffee samples, a coffee cup, pens or a similar token. However, during traditional gift-giving seasons in areas where it is customary to exchange gifts of money, such as China, Japan, Malaysia, Singapore and Thailand, partners should not solicit but may exchange cash with nongovernmental business associates in nominal amounts up to the equivalent of US $20. [3]
It is very common for company’s to set a threshold for giving and receiving gifts. These specific guidelines help employees navigate what would otherwise be a judgment call and make it easier to identify an ethical breach and initiate corrective action.
Setting Policy
United Parcel Service (UPS) groups the sections of its Code of Business Conduct into stakeholder groups: our company, our people, our customers, our shareholders, and our communities. This enables the company to address a range of workforce expectations, such as workplace safety:
UPS is committed to a safe work environment that is free of threats, intimidation, and physical harm. Everyone has a right to work in a safe environment and everyone shares the responsibility for ensuring the safety of others. We have zero tolerance for workplace violence, and we will investigate and take appropriate action up to and including dismissal regarding any threats to a safe workplace.
UPS prohibits violent behavior in the workplace including, but not limited to, physical assaults, fighting, threatening comments, intimidation, threats through electronic communications including social media, and the intentional or reckless destruction of property of the company, employee, UPS representative, or customer. Comments or behavior that reasonably could be interpreted as intent to do harm to people or property will be considered a threat. We also prohibit the unauthorized possession and/or use of weapons by any employee or UPS representative while at work, on company property, or while on company business. [4]
The UPS policy is very specific about its expectations of employees in ensuring a safe work environment.
Judgment Calls
No policy will address every issue, nor should it try. Most policies try to guide employees in the way they should make judgment calls. In its Standards of Business Conduct, American Airlines addresses this issue specifically:
Remember, your best resource about what’s right or wrong is your own conscience. So if you find yourself in a difficult situation, think before you act. And ask yourself the following questions:
- Is it legal? If it’s not legal, don’t do it.
- Is it ethical? If it feels wrong, it probably is wrong.
- How would it look in the newspaper? If you wouldn’t feel comfortable if your friends and family knew about your actions, you probably shouldn’t do it. [5]
These policies are an important tool in building a culture of accountability and ethical behavior in a company, but the policies must be upheld by all the employees, and senior leaders play a significant role in reinforcing their importance.
- www.ethics.org/newsite/research/eci-research/nbes/nbes-reports/nbes-2013 ↵
- https://secure.ethicspoint.com/domain/media/en/gui/711/code_en.pdf ↵
- https://globalassets.starbucks.com/assets/eecd184d6d2141d58966319744393d1f.pdf ↵
- www.ups.com/media/en/code_bus_conduct.pdf ↵
- www.aa.com/i18n/amrcorp/corporateInformation/facts/ethics.jsp ↵
Contributors and Attributions
- A Culture of Accountability. Provided by : Lumen Learning. License : CC BY: Attribution


Skip to main content
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agent
-
something physical, chemical, nutritional, psychosocial, or biologic that can cause a health issue; must be present for a disease to occur
-
airborne transmission
-
occurs when infectious agents are capable of remaining suspended in air over long distances and long periods of time, in contrast to droplets that fall to the ground within a few feet
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alpha
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the
p
value or the significance level for the results of a study to be deemed statistically significant
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analytic epidemiology
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the study of the causes and effects of diseases or other health events, looking for the
why
and the
how,
attempting to quantify a relationship between two variables
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attack rate
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the proportion of a population that develops an illness during an outbreak (synonym of
incidence proportion
)
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attributable risk (AR)
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a measurement of the amount of disease among exposed individuals that is attributed to the exposure
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bias
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a systematic error that underestimates or overestimates the value of a parameter; a source of error in a study’s outcome arising in the design or conduct of the study, data collection, or data analysis
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carriers
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individuals with incubating disease or preclinical infection but without overt symptoms who are still capable of transmitting disease
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case-control study
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a study design in which investigators enroll a group of individuals with a disease and a group of individuals without the disease and compare previous exposures between the groups
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case-fatality rate
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the proportion of individuals with a disease who die from it
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causality
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the relationship between cause and effect
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chain of infection
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an epidemiological model that allows for a complex and nuanced interplay between the host, agent, and environment of the epidemiological triad
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chance
-
a random error in a study
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clinical disease stage
-
stage within the natural history of disease during which signs of the disease develop and diagnosis may occur
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cohort study
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a study in which the investigator documents whether or not study participants were exposed to what is being studied
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confidence intervals
-
the relative risk (or other risk measure) found in the study and an interval within which the risk would most likely fall if the study were repeated multiple times
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confounding
-
a type of error that may result in an incorrect causation or conclusion
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cross-sectional study
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a study in which a sample of individuals from a specified population is enrolled and the exposure and disease outcome are measured simultaneously for each participant; provides a snapshot of any specified population at a given point in time
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death-to-case ratio
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the number of deaths attributed to a disease during a specific period of time divided by the number of new cases of that disease during the same period
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descriptive epidemiology
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the frequency and pattern of health events within a population according to the characteristics of person, place, and time
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direct transmission
-
transmission of an infectious agent from a reservoir to a host by direct contact or droplet spread of infected material
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droplet spread
-
infected material transmitted by direct spray of relatively large, short-range aerosols of the pathogen over a few feet prior to the droplets falling to the ground
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endemic
-
the continual and constant presence of a disease within a given geographic area
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environmental factors
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in the epidemiologic triad, the biologic environment of plants, animals, and toxins, including vectors that carry infectious agents and the reservoirs where infectious agents are normally found
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epidemic
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when the level of disease in a defined area rises above endemic levels
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epidemiological triad
-
a model of disease causation; classically describes disease as a result of the relationship between a susceptible host, an external agent, and an environment bringing the host and agent together
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epidemiology
-
scientific study of the distribution and determinants of diseases and health outcomes in populations
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experimental studies
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in epidemiology, studies in which the investigator controls or changes the factors thought to cause a health event and then observes what happens to the health state
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health events
-
disease, injury, or death
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host
-
an individual, a family, a group of high-risk individuals, or a community within the context of the epidemiological triad
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hyperendemic
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persistent high levels of disease in a defined area
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incidence proportion
-
the proportion of a population that develops an illness during an outbreak (synonym of attack rate)
-
incidence rate
-
during a given time period, all new cases of a disease or health condition divided by the population at risk
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indirect transmission
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transmission that occurs when an infectious agent is transmitted from a reservoir to a host by suspended air particles, inanimate objects also known as vehicles, or vector intermediaries
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morbidity
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having a disease, illness, or medical condition; includes disease, injury, and disability
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mortality rate
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the frequency of death in a defined population during a specific time interval
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natural history of disease
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events that occur before development of a disease, during the course of the disease, and at the conclusion of the disease
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observational studies
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epidemiological studies based on investigator observations of exposure and disease status
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odds ratio (OR)
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odds a case was exposed divided by the odds a control was exposed; quantitatively expresses the association between an exposure and a disease or health outcome; most often used to estimate the relative risk in case-control studies when the disease being investigated is rare
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outbreak
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an epidemic affecting a limited geographic area
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p
value
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the probability that an observed association could be the result of random error
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pathogenicity
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the ability of an agent to cause disease, influencing disease onset
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portal of entry
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how an agent infects a susceptible host
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portal of exit
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how an agent leaves its home base in the chain of causation/infection
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prevalence rate
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proportion of a population that has a health condition at a certain point in time or over a time interval
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proportion
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a form of a ratio in which the numerator represents a subset of the denominator
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rate ratio
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compares the incidence rates or mortality rates of two groups
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ratio
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a comparison of any two values, calculated by dividing one interval by the other
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relative risk (RR)
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the ratio of the incidence proportion of the health event in exposed individuals (or the group of primary interest) to the incidence proportion in unexposed individuals (or the comparison group); compares the risk of a health event among one group with the risk among another group; see also risk ratio
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reservoir
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where the causal agent normally lives and reproduces in the chain of causation
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risk ratio
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synonym of
relative risk
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sample size
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the number of participants in a study
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sporadic
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diseases that occur at irregular intervals
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spot map
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a type of epidemiological map that shows the geographic distribution of cases of illness or disease by marking each case with a dot on a map
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statistical significance
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an assessment for random error in a study
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subclinical disease stage
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the natural history of disease stage after exposure but prior to clinical disease in which individuals have pathologic change but no overt symptoms
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susceptibility stage
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the initial interactions between the agent, host, and environment during the pre-pathogenesis period, during which time primary prevention measures could be implemented to prevent disease onset


5.4: Balancing
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When entries that are already sorted are stored in a tree, all new records will go the same route, and the tree will look more like a list (such a tree is called a degenerate tree). Therefore the tree needs balancing routines, making sure that under all branches are an equal number of records. This will keep searching in the tree at optimal speed. Specifically, if a tree with n nodes is a degenerate tree, the longest path through the tree will be n nodes; if it is a balanced tree, the longest path will be log n nodes.
Algorithms/Left rotation : This shows how balancing is applied to establish a priority heap invariant in a Treap, a data structure which has the queueing performance of a heap, and the key lookup performance of a tree. A balancing operation can change the tree structure while maintaining another order, which is binary tree sort order. The binary tree order is left to right, with left nodes' keys less than right nodes' keys, whereas the priority order is up and down, with higher nodes' priorities greater than lower nodes' priorities. Alternatively, the priority can be viewed as another ordering key, except that finding a specific key is more involved.
The balancing operation can move nodes up and down a tree without affecting the left right ordering.


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Ecosystem conservation and management involves three different activities: (1) monitoring ecosystem components, (2) maintaining healthy ecosystems, and (3) restoring damaged ecosystems.
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An ecosystem in which all the chemical, physical, and biological components and processes are functioning normally is considered healthy. Ecosystems that remain healthy through disturbance are resistant, while ecosystems that rapidly recover after disturbance are resilient.
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Ecosystems can be monitored using direct observation, environmental or biochemical indicators, and remote sensing analysis. It is important that any monitoring method be consistent and repeatable across space and time.
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To maintain ecosystems that can support diverse ecological communities, conservationists are guided by three complementary management principles: (1) maintain critical ecosystem processes (water cycling, nutrient cycling, energy flow, community dynamics), (2) minimise external threats, and (3) be adaptive yet minimally intrusive.
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Ecological restoration is the practice of restoring damaged ecosystems to an agreed-upon benchmark. This can be accomplished via rehabilitation, partial restoration, complete restoration, or taking no action. The strategy followed will depend on each project’s goals and resource availability.


22.8: Poe and King sitting on a throne of skulls
I have always believed Edgar Allan Poe and Stephen King were the kings of American Gothic Literature, both of them sitting on a throne made up of skulls and bones together because I couldn’t pick one or the other. American Gothic to me is the written words that make your skin crawl and your heart beat a little faster. It’s not about someone wearing black and walking creepily. It’s about the deep descriptions of something like a heart beating underneath the floorboards.  For example, Edgar Allan Poe’s The Narrative of Arthur Gordon Pym, the four men have to decide who is going to die to quench their thirst and starvation. “Let it suffice to say that, having in some measure appeased the raging thirst which consumed us by the blood of the victim, and having by the common consent taken off the hands, feet, and head, throwing them, together with entrails, into the sea, we devoured the rest of the body (Poe 81). To me, it’s the word choice in making the situation that is already gothic more alive to readers: raging, consumed, victim, entrails, devoured.
American Literature texts such as Benito Cereno could be considered to have gothic examples but the overall text is not gothic; I can only pick out one or two descriptions from the book that are gothic while in Poe’s, The Narrative of Arthur Gordon Pym of Nantucket I can pick out more than I can count on both hands. British Gothic Literature has a lot of the same characteristics as American Gothic Literature, such as supernatural beings such as ghosts, curses and prophecies. But one thing that is different in the two is that British Gothic Literature includes a lot of romance while American Gothic doesn’t as much.
When I think of an original British Gothic text, I think of Dracula . It was supposed to be creepy in that vampires are dark human beings looking to drink your blood but in the original book the women who was getting her blood drank was always made out to be sexy and weak to bring in the romance. Not to say American Gothic Literature doesn’t have romance but British Gothic has so much more. American Literature does have the Twilight series but there was also a lot of Edgar Allan Poe kind of goth in the books when the main character, Bella was getting her leg snapped. Poe shows so much gothic literature in Pym just by describing simple things like the water having eyes, or the majestic appearance of the animal they found. It’s more about his descriptions of things rather than just the action taking place itself. Poe could make anything gothic with his descriptions, even a normal morning jog.


23.2: Anatomy of the Male Reproductive System
By the end of the section, you will be able to:
- Describe the structure and function of the organs of the male reproductive system
- Describe the structure and function of the sperm cell
- Explain the events during spermatogenesis that produce haploid sperm from diploid cells
- Identify the importance of testosterone in male reproductive function
Unique for its role in human reproduction, a gamete is a specialized sex cell carrying 23 chromosomes—one half the number in body cells. At fertilization, the chromosomes in one male gamete, called a sperm (or spermatozoon), combine with the chromosomes in one female gamete, called an oocyte. The function of the male reproductive system is to produce sperm and transfer them to the female reproductive tract. The structures of the male reproductive system include the testes, the epididymides, the penis, and the ducts and glands that produce and carry semen (Figure 23.2.1). Sperm exit the scrotum through the ductus deferens, which is bundled in the spermatic cord. The spermatic cord is comprised of the ductus deferens, testicular artery, autonomic nerve, lymphatic vessel, and plexus of testicular veins. The seminal vesicles and prostate gland add fluids to the sperm to create semen. The paired testes are a crucial component in this process, as they produce both sperm and androgens, the hormones that support male reproductive physiology. In humans, the most important male androgen is testosterone. Several accessory organs and ducts aid the process of sperm maturation and transport the sperm and other seminal components to the penis, which delivers sperm to the female reproductive tract. In this section, we examine each of these different structures, and discuss the process of sperm production and transport. Details about these male anatomical structures will be discussed below.
Scrotum
The testes are located in a skin-covered, highly pigmented, muscular sack called the scrotum that extends from the body behind the penis (see Figure 23.2.1). This location is important in sperm production, which occurs within the testes, and proceeds more efficiently when the testes are kept 2 to 4°C below core body temperature.
The dartos muscle makes up the subcutaneous muscle layer of the scrotum (Figure 23.2.2). It continues internally to make up the scrotal septum, a wall that divides the scrotum into two compartments, each housing one testis. Descending from the internal oblique muscle of the abdominal wall are the two cremaster muscles , which cover each testis like a muscular net. By contracting simultaneously, the dartos and cremaster muscles can elevate the testes in cold weather (or water), moving the testes closer to the body and decreasing the surface area of the scrotum to retain heat. Alternatively, as the environmental temperature increases, the scrotum relaxes, moving the testes farther from the body core and increasing scrotal surface area, which promotes heat loss. Externally, the scrotum has a raised medial thickening on the surface called the raphe.
 They produce both sperm and androgens, such as testosterone, and are active throughout the reproductive lifespan of the male.
Paired ovals, the testes are each approximately 4 to 5 cm in length and are housed within the scrotum (see Figure 23.2.2). They are surrounded by two distinct layers of protective connective tissue. Immediately deep to the cremaster muscle is the tunica vaginalis. The outer tunica vaginalis is a serous membrane that has both a parietal and a thin visceral layer. Beneath the tunica vaginalis is the tunica albuginea , a tough, white, dense connective tissue layer covering the testis itself. Not only does the tunica albuginea cover the outside of the testis, it also invaginates to form septa that divide the testis into 300 to 400 structures called lobules . Within the lobules, sperm develop in structures called seminiferous tubules (Figure 23.2.3). During the seventh month of the developmental period of a male fetus, each testis moves through the abdominal musculature to descend into the scrotal cavity. This is called the “descent of the testis.” Cryptorchidism is the clinical term used when one or both of the testes fail to descend into the scrotum prior to birth.
The tightly coiled seminiferous tubules form the bulk of each testis. They are composed of developing sperm cells surrounding a lumen, the hollow center of the tubule, where formed sperm are released into the duct system of the testis. Specifically, from the lumens of the seminiferous tubules, sperm move into the straight tubules (or tubuli recti), and from there into a fine meshwork of tubules called the rete testes . Sperm leave the rete testes, and the testis itself, through the 15 to 20 efferent ductules that cross the tunica albuginea.
Interstitial cells (also known as Leydig cells ) produce testosterone and are located in between the seminiferous tubules (Figure 23.2.4) Inside the seminiferous tubules are six different cell types. These include supporting cells called sustentacular cells , as well as five types of developing sperm cells called germ cells . Germ cell development progresses from the basement membrane—at the perimeter of the tubule—toward the lumen. Let’s look more closely at these cell types.
Sertoli Cells
Surrounding all stages of the developing sperm cells are elongate, branching Sertoli cells ( Figure 23.2.4). Sertoli cells are a type of supporting cell called sustentacular cells, or sustenocyte, that are typically found in epithelial tissue.  Sertoli cells (also known as nurse cells) produce androgen- binding protein. This is needed for testosterone to actually have effects on the developing sperm. These cells also produce inhibin - this feeds back to the anterior pituitary gland to regulate sperm production. They extend physically around the germ cells from the peripheral basement membrane of the seminiferous tubules to the lumen. Tight junctions between these sustentacular cells create the blood–testis barrier , which keeps bloodborne substances from reaching the germ cells and, at the same time, keeps surface antigens on developing germ cells from escaping into the bloodstream and prompting an autoimmune response.
Germ Cells
The least mature cells, the spermatogonia (singular = spermatogonium), line the basement membrane inside the tubule. Spermatogonia are the stem cells of the testis, which means that they are still able to differentiate into a variety of different cell types throughout adulthood. Spermatogonia divide to produce primary and secondary spermatocytes , then spermatids , which finally produce formed sperm. The process that begins with spermatogonia and concludes with the production of sperm is called spermatogenesis .
Spermatogenesis
As just noted, spermatogenesis occurs in the seminiferous tubules that form the bulk of each testis (Figure 23.2.3). The process begins at puberty, after which time sperm are produced constantly throughout a man’s life. One production cycle, from spermatogonia through formed sperm, takes approximately 64 days. A new cycle starts approximately every 16 days, although this timing is not synchronous across the seminiferous tubules. Sperm counts—the total number of sperm a man produces—slowly decline after age 35, and some studies suggest that smoking can lower sperm counts irrespective of age.
The process of spermatogenesis begins with mitosis of the diploid spermatogonia in which one spermatogonium becomes two primary spermatocytes. Because these cells are diploid (2 n ), they each have a complete copy of the father’s genetic material, or 46 chromosomes. After mitosis, the primary spermatocytes begin the two rounds of meiosis, i.e. meiosis I resulting in secondary spermatocytes, and meiosis II, resulting in spermatids. Mature gametes are haploid (1 n ), containing 23 chromosomes—meaning that daughter cells of spermatogonia must undergo a second cellular division through the process of meiosis Figure 23.2.4). These spermatids will continue with spermiogenesis to become spermatozoa, also known as sperm. A cross section of a seminiferous tubule will show the early cells of spermatogenesis at the outer edge and the more mature cells migrating toward the lumen in the center.
Two identical diploid cells result from spermatogonia mitosis. One of these cells remains a spermatogonium, and the other becomes a primary spermatocyte , the next stage in the process of spermatogenesis. As in mitosis, DNA is replicated in a primary spermatocyte, and the cell undergoes cell division to produce two cells with identical chromosomes. Each of these is a secondary spermatocyte . Now a second round of cell division occurs in both of the secondary spermatocytes, separating the chromosome pairs. This second meiotic division results in a total of four cells with only half of the number of chromosomes. Each of these new cells is a spermatid . Although haploid, early spermatids look very similar to cells in the earlier stages of spermatogenesis, with a round shape, central nucleus, and large amount of cytoplasm. A process called spermiogenesis transforms these early spermatids, reducing the cytoplasm, and beginning the formation of the parts of a true sperm. The fifth stage of germ cell formation— spermatozoa , or formed sperm—is the end result of this process, which occurs in the portion of the tubule nearest the lumen. Eventually, the sperm are released into the lumen and are moved along a series of ducts in the testis toward a structure called the epididymis for the next step of sperm maturation.
Structure of Formed Sperm
Sperm are smaller than most cells in the body; in fact, the volume of a sperm cell is 85,000 times less than that of the female gamete. Approximately 100 to 300 million sperm are produced each day, whereas women typically ovulate only one oocyte per month as is true for most cells in the body, the structure of sperm cells speaks to their function. The head of the sperm contains the extremely compact haploid nucleus with very little cytoplasm (Figure 23.2.5). These qualities contribute to the overall small size of the sperm (the head is only 5 μ m long). A structure called the acrosome covers most of the head of the sperm cell as a “cap” that is filled with lysosomal enzymes important for preparing sperm to participate in fertilization. Tightly packed mitochondria fill the mid-piece of the sperm. ATP produced by these mitochondria will power the flagellum, which extends from the neck and the mid-piece through the tail of the sperm, enabling it to move the entire sperm cell. The central strand of the flagellum, the axial filament, is formed from one centriole inside the maturing sperm cell during the final stages of spermatogenesis.
Sperm Transport
To fertilize an egg, sperm must be moved from the seminiferous tubules in the testes, through the epididymis, and—later during ejaculation—along the length of the penis and out into the female reproductive tract.
Role of the Epididymis
From the lumen of the seminiferous tubules, the immotile sperm are surrounded by testicular fluid and moved to the epididymis (plural = epididymides), a coiled tube attached to the testis where newly formed sperm continue to mature (see Figure 23.2.3). Though the epididymis does not take up much room in its tightly coiled state, it would be approximately 6 m (20 feet) long if straightened. It takes an average of 12 days for sperm to move through the coils of the epididymis, with the shortest recorded transit time in humans being one day. Sperm enter the head of the epididymis and are moved along predominantly by the contraction of smooth muscles lining the epididymal tubes. The more mature sperm are then stored in the tail of the epididymis (the final section) until ejaculation occurs.
Duct System
During ejaculation, sperm exit the tail of the epididymis and are pushed by smooth muscle contraction to the ductus deferens (also called the vas deferens). The ductus deferens is a thick, muscular tube that is bundled together inside the scrotum with connective tissue, blood vessels, and nerves into a structure called the spermatic cord (see Figure 23.2.1 and Figure 23.2.2). Because the ductus deferens is physically accessible within the scrotum, surgical sterilization to interrupt sperm delivery can be performed by cutting and sealing a small section of the ductus (vas) deferens. This procedure is called a vasectomy , and it is an effective form of male birth control. Although it may be possible to reverse a vasectomy, clinicians consider the procedure permanent, and advise men to undergo it only if they are certain they no longer wish to father children.
Interactive Element
Watch this video Vasectomy to learn about a procedure in which a small section of the ductus (vas) deferens is removed from the scrotum. This interrupts the path taken by sperm through the ductus deferens. If sperm do not exit through the vas, either because the man has had a vasectomy or has not ejaculated, in what region of the testis do they remain?
Answer
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Answer: Sperm remain in the epididymis until they degenerate
From each epididymis, each ductus deferens extends superiorly into the abdominal cavity through the inguinal canal in the abdominal wall. From here, the ductus deferens continues posteriorly to the pelvic cavity, ending posterior to the bladder where it dilates in a region called the ampulla (meaning “flask”).
Sperm make up only 5 percent of the final volume of semen , the thick, milky fluid that the male ejaculates. The bulk of semen is produced by three critical accessory glands of the male reproductive system: the seminal vesicles, the prostate, and the bulbourethral glands (Figure 23.2.6).
Seminal Vesicles
As sperm pass through the ampulla of the ductus deferens at ejaculation, they mix with fluid from the associated seminal vesicle (see Figure 23.2.6). The paired seminal vesicles are glands that contribute approximately 60 percent of the semen volume. Seminal vesicle fluid contains large amounts of fructose, which is used by the sperm mitochondria to generate ATP to allow movement through the female reproductive tract. Sperm are immobile until mixed with secretions of the seminal glands.
The fluid, now containing both sperm and seminal vesicle secretions, next moves into the associated ejaculatory duct , a short structure formed from the ampulla of the ductus deferens and the duct of the seminal vesicle. The paired ejaculatory ducts transport the seminal fluid into the next structure, the prostate gland.
Prostate Gland
As shown in Figure 23.2.6, the centrally located prostate gland sits anterior to the rectum at the base of the bladder surrounding the prostatic urethra (the portion of the urethra that runs within the prostate). About the size of a walnut, the prostate is formed of both muscular and glandular tissues. It excretes an alkaline, milky fluid to the passing seminal fluid—now called semen—that is critical to first coagulate and then decoagulate the semen following ejaculation. The temporary thickening of semen helps retain it within the female reproductive tract, providing time for sperm to utilize the fructose provided by seminal vesicle secretions. When the semen regains its fluid state, sperm can then pass farther into the female reproductive tract.
The prostate normally doubles in size during puberty. At approximately age 25, it gradually begins to enlarge again. This enlargement does not usually cause problems; however, abnormal growth of the prostate, or benign prostatic hyperplasia (BPH), can cause constriction of the urethra as it passes through the middle of the prostate gland, leading to a number of lower urinary tract symptoms, such as a frequent and intense urge to urinate, a weak stream, and a sensation that the bladder has not emptied completely. By age 60, approximately 40 percent of men have some degree of BPH. By age 80, the number of affected individuals has jumped to as many as 80 percent. Treatments for BPH attempt to relieve the pressure on the urethra so that urine can flow more normally. Mild to moderate symptoms are treated with medication, whereas severe enlargement of the prostate is treated by surgery in which a portion of the prostate tissue is removed.
Another common disorder involving the prostate is prostate cancer. According to the Centers for Disease Control and Prevention (CDC), prostate cancer is the second most common cancer in men. However, some forms of prostate cancer grow very slowly and thus may not ever require treatment. Aggressive forms of prostate cancer, in contrast, involve metastasis to vulnerable organs like the lungs and brain. There is no link between BPH and prostate cancer, but the symptoms are similar. Prostate cancer is detected by a medical history, a blood test, and a rectal exam that allows physicians to palpate the prostate and check for unusual masses. If a mass is detected, the cancer diagnosis is confirmed by biopsy of the cells.
Bulbourethral Glands
The final addition to semen is made by two bulbourethral glands (or Cowper’s glands) that release a thick, salty fluid that lubricates the end of the urethra and the vagina, and helps to clean urine residues from the penile urethra. The fluid from these accessory glands is released after the male becomes sexually aroused, and shortly before the release of the semen. It is therefore sometimes called pre-ejaculate. It is important to note that, in addition to the lubricating proteins, it is possible for bulbourethral fluid to pick up sperm already present in the urethra, and therefore it may be able to cause pregnancy. Once inside the female reproductive tract, sperm will move toward the unfertilized egg and will undergo chemical changes called capacitation in order to fertilize the egg. Capacitation involves destabilization of the acrosomal membrane of the sperm head and greater mobility in the sperm's tail to permit fertilization.
 Where are sperm deposited after they leave the ejaculatory duct?
Answer
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Answer: Sperm enter the prostate.
 It is flaccid for non-sexual actions, such as urination, and turgid and rod-like with sexual arousal. When erect, the stiffness of the organ allows it to penetrate into the vagina and deposit semen into the female reproductive tract (Figure 23.2.7).
 The shaft is composed of three column-like chambers of erectile tissue that span the length of the shaft. Each of the two larger lateral chambers is called a corpus cavernosum (plural = corpora cavernosa). Together, these make up the bulk of the penis. The corpus spongiosum , which can be felt as a raised ridge on the erect penis, is a smaller chamber that surrounds the spongy, or penile, urethra. The end of the penis, called the glans penis , has a high concentration of nerve endings, resulting in very sensitive skin that influences the likelihood of ejaculation (see Figure 23.2.7). The skin from the shaft extends down over the glans and forms a collar called the prepuce (or foreskin). The foreskin also contains a dense concentration of nerve endings, and both lubricate and protect the sensitive skin of the glans penis. A surgical procedure called circumcision, often performed for religious or social reasons, removes the prepuce, typically within days of birth.
Both sexual arousal and REM sleep (during which dreaming occurs) can induce an erection.  During sexual arousal, nitric oxide (NO) is released from nerve endings near blood vessels within the corpora cavernosa and spongiosum. Release of NO activates a signaling pathway that results in relaxation of the smooth muscles that surround the penile arteries, causing them to dilate. This dilation increases the amount of blood that can enter the penis and induces the endothelial cells in the penile arterial walls to also secrete NO and perpetuate the vasodilation. The rapid increase in blood volume fills the erectile chambers, and the increased pressure of the filled chambers compresses the thin-walled penile venules, preventing venous drainage of the penis.
Male Reproductive System
Erectile dysfunction (ED) is a condition in which a man has difficulty either initiating or maintaining an erection. The combined prevalence of minimal, moderate, and complete ED is approximately 40 percent in men at age 40, and reaches nearly 70 percent by 70 years of age. In addition to aging, ED is associated with diabetes, vascular disease, psychiatric disorders, prostate disorders, the use of some drugs such as certain antidepressants, and problems with the testes resulting in low testosterone concentrations. These physical and emotional conditions can lead to interruptions in the vasodilation pathway and result in an inability to achieve an erection.
Recall that the release of NO induces relaxation of the smooth muscles that surround the penile arteries, leading to the vasodilation necessary to achieve an erection. To reverse the process of vasodilation, an enzyme called phosphodiesterase (PDE) degrades a key component of the NO signaling pathway called cGMP. There are several different forms of this enzyme, and PDE type 5 is the type of PDE found in the tissues of the penis.
PDEs and the vasodilation signaling pathway are found in the vasculature in other parts of the body. In the 1990s, clinical trials of a PDE5 inhibitor called sildenafil were initiated to treat hypertension and angina pectoris (chest pain caused by poor blood flow through the heart). The trial showed that the drug was not effective at treating heart conditions, but many men experienced erection and priapism (erection lasting longer than 4 hours). Because of this, a clinical trial was started to investigate the ability of sildenafil to promote erections in men suffering from ED. In 1998, the FDA approved the drug, marketed as Viagra®. Since approval of the drug, sildenafil and similar PDE inhibitors now generate over a billion dollars a year in sales, and are reported to be effective in treating approximately 70 to 85 percent of cases of ED. Importantly, men with health problems—especially those with cardiac disease taking nitrates—should avoid Viagra or talk to their physician to find out if they are a candidate for the use of this drug, as deaths have been reported for at-risk users.
Testosterone
Testosterone, an androgen, is a steroid hormone produced by Leydig cells . The alternate term for Leydig cells, interstitial cells, reflects their location between the seminiferous tubules in the testes. In male embryos, testosterone is secreted by Leydig cells by the seventh week of development, with peak concentrations reached in the second trimester. This early release of testosterone results in the anatomical differentiation of the male sexual organs. In childhood, testosterone concentrations are low. They increase during puberty, activating characteristic physical changes and initiating spermatogenesis.
Functions of Testosterone
The continued presence of testosterone is necessary to keep the male reproductive system working properly, and Leydig cells produce approximately 6 to 7 mg of testosterone per day. Testicular steroidogenesis (the manufacture of androgens, including testosterone) results in testosterone concentrations that are 100 times higher in the testes than in the circulation. Maintaining these normal concentrations of testosterone promotes spermatogenesis, whereas low levels of testosterone can lead to infertility. In addition to intratesticular secretion, testosterone is also released into the systemic circulation and plays an important role in muscle development, bone growth, the development of secondary sex characteristics, and maintaining libido (sex drive) in both males and females. In females, the ovaries secrete small amounts of testosterone, although most is converted to estradiol. A small amount of testosterone is also secreted by the adrenal glands in both sexes.
Control of Testosterone
The regulation of testosterone concentrations throughout the body is critical for male reproductive function. The regulation of Leydig cell production of testosterone begins outside of the testes. The hypothalamus and the pituitary gland in the brain integrate external and internal signals to control testosterone synthesis and secretion. The regulation begins in the hypothalamus . Pulsatile release of a hormone called gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates the endocrine release of hormones from the pituitary gland. Binding of GnRH to its receptors on the anterior pituitary gland stimulates release of the two gonadotropins: luteinizing hormone (LH) and follicle-stimulating hormone (FSH) . These two hormones are critical for reproductive function in both men and women. In men, FSH binds predominantly to the Sertoli cells within the seminiferous tubules to promote spermatogenesis. FSH also stimulates the Sertoli cells to produce hormones called inhibins, which function to inhibit FSH release from the pituitary, thus reducing testosterone secretion. These polypeptide hormones correlate directly with Sertoli cell function and sperm number; inhibin can be used as a marker of spermatogenic activity. In men, LH binds to receptors on Leydig cells in the testes and upregulates the production of testosterone. Please refer to the Endocrine System, Sections 15.3 and 15.8 for additional details.
AGING AND THE...
Male Reproductive System
Declines in Leydig cell activity can occur in men beginning at 40 to 50 years of age. The resulting reduction in circulating testosterone concentrations can lead to symptoms of andropause, also known as male menopause. While the reduction in sex steroids in men is akin to female menopause, there is no clear sign—such as a lack of a menstrual period—to denote the initiation of andropause. Instead, men report feelings of fatigue, reduced muscle mass, depression, anxiety, irritability, loss of libido, and insomnia. A reduction in spermatogenesis resulting in lowered fertility is also reported, and sexual dysfunction can also be associated with andropausal symptoms.
Whereas some researchers believe that certain aspects of andropause are difficult to tease apart from aging in general, testosterone replacement is sometimes prescribed to alleviate some symptoms. Recent studies have shown a benefit from androgen replacement therapy on the new onset of depression in elderly men; however, other studies caution against testosterone replacement for long-term treatment of andropause symptoms, showing that high doses can sharply increase the risk of both heart disease and prostate cancer.
Concept Review
Gametes are the reproductive cells that combine to form offspring. Organs called gonads produce the gametes, along with the hormones that regulate human reproduction. The male gametes are called sperm. Spermatogenesis, the production of sperm, occurs within the seminiferous tubules that make up most of the testis. The scrotum is the muscular sac that holds the testes outside of the body cavity.
Spermatogenesis begins with mitotic division of spermatogonia (stem cells) to produce primary spermatocytes that undergo the two divisions of meiosis to become secondary spermatocytes, then the haploid spermatids. During spermiogenesis, spermatids are transformed into spermatozoa (formed sperm). Upon release from the seminiferous tubules, sperm are moved to the epididymis where they continue to mature. During ejaculation, sperm exit the epididymis through the ductus deferens, a duct in the spermatic cord that leaves the scrotum. The ampulla of the ductus deferens meets the seminal vesicle, a gland that contributes fructose and proteins, at the ejaculatory duct. The fluid continues through the prostatic urethra, where secretions from the prostate are added to form semen. These secretions help sperm to travel through the urethra and into the female reproductive tract. Secretions from the bulbourethral glands protect sperm and cleanse and lubricate the penile (spongy) urethra.
  Testosterone regulates and maintains the sex organs and sex drive, and induces the physical changes of puberty. Interplay between the testes and the endocrine system precisely control the production of testosterone.
Review Questions
Q. What are male gametes called?
A. ova
B. sperm
C. testes
D. testosterone
- Answer
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Answer: B
Q. Leydig cells ________.
A. are found in between seminiferous tubules
B. activate the sperm flagellum
C. are spermatogonia
D. secrete seminal fluid
- Answer
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Answer: A
Q. Which structure is affected in a vasectomy?
A. testis
B. ductus deferens
C. prostate gland
D. epididymis
- Answer
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Answer: B
Q. Where is the epididymis?
A. in the scrotum
B. in the testes
C. posterior to the bladder
D. inside the pelvis
- Answer
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Answer: A
Q. Which muscle(s) surround(s) the testes?
A. cremaster
B. dartos
C. A & B
D. smooth muscle
- Answer
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Answer: C
Critical Thinking Questions
Q. Briefly explain why mature gametes carry only one set of chromosomes.
- Answer
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A. Humans have 46 chromosomes. Meiosis is cell division that produces sperm (gametes) with only 23 chromosomes. A single gamete must combine with a gamete from an individual of the opposite sex to produce a fertilized egg, which has a complete set of chromosomes (46) and is the first cell of a new individual.
Q. What special features are evident in sperm cells but not in somatic cells, and how do these specializations function?
- Answer
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A. Unlike somatic cells, sperm are haploid with 23 chromosomes. They also have very little cytoplasm.  They are motile because of their tail, a structure containing a flagellum, which is specialized for movement to find the egg for fertilization.
Q. Name three male accessory glands and explain how each contributes to the semen.
- Answer
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A. The three accessory glands make the following contributions to semen: the seminal vesicle contributes about 60 percent of the semen volume, with fluid that contains large amounts of fructose to power the movement of sperm; the prostate gland contributes substances critical to sperm maturation; and the bulbourethral glands contribute a thick fluid that lubricates the ends of the urethra and the vagina and helps to clean urine residues from the urethra.
Q. Describe how penile erection occurs.
- Answer
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A. During sexual arousal, nitric oxide (NO) is released from nerve endings near blood vessels within the corpora cavernosa and corpus spongiosum. The release of NO activates a signaling pathway that results in relaxation of the smooth muscles that surround the penile arteries, causing them to dilate. This dilation increases the amount of blood that can enter the penis, and induces the endothelial cells in the penile arterial walls to secrete NO, perpetuating the vasodilation. The rapid increase in blood volume fills the erectile chambers, and the increased pressure of the filled chambers compresses the thin-walled penile venules, preventing venous drainage of the penis.
Glossary
- blood–testis barrier
- tight junctions between Sertoli cells that prevent bloodborne pathogens from gaining access to later stages of spermatogenesis and prevent the potential for an autoimmune reaction to haploid sperm
- bulbourethral glands
- (also, Cowper’s glands) glands that secrete a lubricating mucus that cleans and lubricates the urethra prior to and during ejaculation
- corpus cavernosum
- either of two columns of erectile tissue in the penis that fill with blood during an erection
- corpus spongiosum
- (plural = corpora cavernosa) column of erectile tissue in the penis that fills with blood during an erection and surrounds the penile urethra on the ventral portion of the penis
- ductus deferens
- (also, vas deferens) duct that transports sperm from the epididymis through the spermatic cord and into the ejaculatory duct; also referred as the vas deferens
- ejaculatory duct
- duct that connects the ampulla of the ductus deferens with the duct of the seminal vesicle at the prostatic urethra
- epididymis
- (plural = epididymides) coiled tubular structure in which sperm start to mature and are stored until ejaculation
- gamete
- haploid reproductive cell that contributes genetic material to form an offspring
- glans penis
- bulbous end of the penis that contains a large number of nerve endings
- gonadotropin-releasing hormone (GnRH)
- hormone released by the hypothalamus that regulates the production of follicle-stimulating hormone and luteinizing hormone from the pituitary gland
- gonads
- reproductive organs (testes in men and ovaries in women) that produce gametes and reproductive hormones
- inguinal canal
- opening in abdominal wall that connects the testes to the abdominal cavity
- Leydig cells
- cells between the seminiferous tubules of the testes that produce testosterone; a type of interstitial cell
- penis
- male organ of copulation
- prepuce
- (also, foreskin) flap of skin that forms a collar around, and thus protects and lubricates, the glans penis; also referred as the foreskin
- prostate gland
- doughnut-shaped gland at the base of the bladder surrounding the urethra and contributing fluid to semen during ejaculation
- scrotum
- external pouch of skin and muscle that houses the testes
- semen
- ejaculatory fluid composed of sperm and secretions from the seminal vesicles, prostate, and bulbourethral glands
- seminal vesicle
- gland that produces seminal fluid, which contributes to semen
- seminiferous tubules
- tube structures within the testes where spermatogenesis occurs
- Sertoli cells
- cells that support germ cells through the process of spermatogenesis; a type of sustentacular cell
- sperm
- (also, spermatozoon) male gamete
- spermatic cord
- bundle of nerves and blood vessels that supplies the testes; contains ductus deferens
- spermatid
- immature sperm cells produced by meiosis II of secondary spermatocytes
- spermatocyte
- cell that results from the division of spermatogonium and undergoes meiosis I and meiosis II to form spermatids
- spermatogenesis
- formation of new sperm, occurs in the seminiferous tubules of the testes
- spermatogonia
- (singular = spermatogonium) diploid precursor cells that become sperm
- spermiogenesis
- transformation of spermatids to spermatozoa during spermatogenesis
- testes
- (singular = testis) male gonads
Contributors and Attributions
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OpenStax Anatomy & Physiology (CC BY 4.0). Access for free at https://openstax.org/books/anatomy-and-physiology