3.4: Reading Textbooks
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Dave Dillon
“There is more treasure in books than in all the pirate’s loot on Treasure Island.”
– Walt Disney
Practice
If you want to be a better swimmer, you practice. If you want to be a better magician, you practice. If you want to be a better reader, you practice. I encourage you to read. Read, read, read. Read newspapers. Read magazines. Read books. Use your library card (get one if you don’t have one). Read blogs. Read tweets. Read Wikipedia articles. Read about history, politics, world leaders, current events, sports, art, music—whatever interests you. Why? Because the more you read, the better reader you become. And because the more you read, the more knowledge you will have. That is an important piece in learning and understanding. When we are learning new information, it’s easier to learn if we have some kind of background knowledge about it.
Background Knowledge
In their book, Content Area Reading: Literacy and Learning Across the Curriculum , Vacca and Vacca postulate that a student’s prior knowledge is “the single most important resource in learning with texts.” [1]
Reading and learning are processes that work together. Students draw on prior knowledge and experiences to make sense of new information. “Research shows that if learners have advanced knowledge of how the information they’re about to learn is organized — if they see how the parts relate to the whole before they attempt to start learning the specifics — they’re better able to comprehend and retain the material.” [2]
For example, you are studying astronomy and the lecture is about Mars. Students with knowledge of what Mars looks like, or how it compares in size to other planets or any information about Mars will help students digest new information and connect it to prior knowledge. The more you read, the more background knowledge you have, and the better you will be able to connect information and learn. “Content overlap between text and knowledge appears to be a necessary condition for learning from text.” [3]
There are a lot of recent advances in technology that have made information more accessible to us. Use this resource! If you are going to read a chemistry textbook, experiment with listening or watching a podcast or a YouTube video on the subject you are studying. Ask your instructor if they recommend specific websites for further understanding.
“The greatest gift is a passion for reading. It is cheap, it consoles, it distracts, it excites, it gives you the knowledge of the world and experience of a wide kind. It is a moral illumination.”
– Elizabeth Hardwick
The Seven Reading Principles
Read the assigned material. I know this sounds like a no-brainer, but you might be surprised to learn how many students don’t read the assigned material. Often, it takes longer to read the material than had been anticipated. Sometimes it is not interesting material to us and we procrastinate reading it. Sometimes we’re busy and it is just not a priority. It makes it difficult to learn the information your instructor wants you to learn if you do not read about it before coming to class.
Read it when assigned. This is almost as big of a problem for students as the first principle. You will benefit exponentially from reading assignments when they are assigned (which usually means reading them before the instructor lectures on them). If there is a date for a reading on your syllabus, finish reading it before that date. The background knowledge you will attain from reading the information will help you learn and connect information when your instructor lectures on it, and it will leave you better prepared for class discussions. Further, if your instructor assigns you 70 pages to read by next week, don’t wait until the night before to read it all. Break it down into chunks. Try scheduling time each day to read 10 or so pages. It takes discipline and self-control but doing it this way will make understanding and remembering what you read much easier.
Take notes when you read. You may recall Hermann Ebbinghaus’ research from a previous chapter. He determined that 42% of information we take in is lost after only 20 minutes without review. For the same reasons that it’s important to take notes during lectures, it’s important to take notes when you are reading. Your notes will help you concentrate, remember and review.
Relate the information to you. We remember information that we deem is important. The strategy then is to make what you are studying important to you. Find a way to directly relate what you are studying to something in your life. Sometimes it is easy and sometimes it is not. But if your attitude is “I will never use this information” and “it’s not important,” chances are good that you will not remember it.
Read with a dictionary or use an online dictionary. Especially with information that is new to us, we may not always recognize all the words in a textbook or their meanings.  Students who read with a dictionary (or who look the word up online) expand their vocabulary and have a better understanding of the text. Take the time to look up words you do not know. Another strategy is to try to determine definitions of unknown words by context, thus eliminating the interruption to look up words.
Ask a classmate or instructor when you have questions or if there are concepts you do not understand. Visiting an instructor’s office hours is one of the most underutilized college resources. I think some students are shy about going, and I understand that, but ultimately, it’s your experience, and it’s up to you if you want to make the most of it. If you go, you will get answers to your questions; at the same time, you’ll demonstrate to your instructor that their course is important to you. Find out when your professor’s office hours are (they are often listed in the syllabus), ask before or after class or e-mail your professor to find out. Be polite and respectful.
Read it again. Some students will benefit from reading the material a second or third time as it allows them to better understand the material. The students who understand the material the best usually score the highest on exams. It may be especially helpful to reread the chapter just after the instructor has lectured on it.
Strategies To Think About When You Open Your Textbook
Preview: Look at what you are reading and how it is connected with other areas of the class. How does it connect with the lecture? How does it connect with the course description? How does it connect with the syllabus or with a specific assignment? What piece of the puzzle are you looking at and how does it fit into the whole picture? If your textbook has a chapter summary, reading it first may help you preview and understand what you are going to be reading.
Headings and designated words: Pay close attention to section headings and subheadings, and boldface, underlined or italicized words and sentences. There is a reason why these are different than regular text. The author feels they are more important and so should you.
Highlighting: Highlighting is not recommended because there is not evidence supporting it helps students with reading comprehension or higher test scores. [4]
Pace: One of the biggest challenges I see students have with reading is accurately assessing how long it will take to read what is assigned. In many cases, it’s important to break the information up in chunks rather than to try and read it all at once. If you procrastinate and leave it until the day before it needs to be read, and then find out it will take you longer than you anticipate, it causes problems. One strategy that works well for many students is to break the information up equally per day and adjust accordingly if it takes longer than you had thought. Accurately estimating how much time it will take to practice the seven reading principles applied to your reading assignments is a skill that takes practice.
“Drink Deeply from Good Books”
– John Wooden
It’s Not All Equal
Keep in mind that the best students develop reading skills that are different for different subjects. The main question you want to ask yourself is: Who are you reading for? And what are the questions that drive the discipline? We read different things for different purposes. Reading texts, blogs, leisure books and textbooks are all different experiences, and we read them with different mindsets and different strategies. The same is true for textbooks in different areas. Reading a mathematics textbook is going to be different than reading a history textbook, a psychology textbook, a Spanish textbook or a criminal justice textbook. Further, students may be assigned to read scientific journals or academic articles often housed in college libraries’ online databases. Scholarly articles require a different kind of reading and librarians are a resource for how to find and read this kind of information. Applying the principles in this chapter will help with your reading comprehension, but it’s important to remember that you will need to develop specific reading skills most helpful to the particular subject you are studying.
Licenses and Attributions:
Content previously copyrighted, published in Blueprint for Success in College: Indispensable Study Skills and Time Management Strategies (by Dave Dillon), now licensed as CC BY Attribution.
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Richard T. Vacca and Jo Anne L. Vacca,
Content Area Reading: Literacy and Learning across the Curriculum
, 6th ed. (Menlo Park, CA: Longman, 1999). ↵
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Joe Cuseo, Viki Fecas and Aaron Thompson,
Thriving in College AND Beyond: Research-Based Strategies for Academic Success and Personal Development,
(Dubuque, IA: Kendal Hunt Publishing, 2010), 115. ↵
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W. Kintsch, “Text Comprehension, Memory, and Learning,”
American Psychologist
49 no. 4 (1994): 294-303,
http://dx.doi.org/10.1037/0003-066X.49.4.294
. ↵
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Lucy Cui, “MythBusters: Highlighting Helps Me Study,” Psychology in Action, accessed April 27, 2018,
https://www.psychologyinaction.org/p...helps-me-study
. ↵


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Chapter 23: The Digestive System
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23.1: Introduction
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The digestive system is continually at work, yet people seldom appreciate the complex tasks it performs in a choreographed biologic symphony.
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23.2: Overview of the Digestive System
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The function of the digestive system is to break down the foods you eat, release their nutrients, and absorb those nutrients into the body. Although the small intestine is the workhorse of the system, where the majority of digestion occurs, and where most of the released nutrients are absorbed into the blood or lymph, each of the digestive system organs makes a vital contribution to this process.
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23.3: Digestive System Processes and Regulation
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The digestive system uses mechanical and chemical activities to break food down into absorbable substances during its journey through the digestive system. The processes of digestion include six activities: ingestion, propulsion, mechanical or physical digestion, chemical digestion, absorption, and defecation.
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23.4: The Mouth, Pharynx, and Esophagus
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In this section, you will examine the anatomy and functions of the three main organs of the upper alimentary canal—the mouth, pharynx, and esophagus—as well as three associated accessory organs—the tongue, salivary glands, and teeth.
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23.5: The Stomach
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Although a minimal amount of carbohydrate digestion occurs in the mouth, chemical digestion really gets underway in the stomach. An expansion of the alimentary canal that lies immediately inferior to the esophagus, the stomach links the esophagus to the first part of the small intestine (the duodenum) and is relatively fixed in place at its esophageal and duodenal ends. In between, however, it can be a highly active structure, contracting and continually changing position and size.
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23.6: The Small and Large Intestines
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The word intestine is derived from a Latin root meaning “internal,” and indeed, the two organs together nearly fill the interior of the abdominal cavity. In addition, called the small and large bowel, or colloquially the “guts,” they constitute the greatest mass and length of the alimentary canal and, with the exception of ingestion, perform all digestive system functions.
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23.7: Accessory Organs in Digestion- The Liver, Pancreas, and Gallbladder
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Chemical digestion in the small intestine relies on the activities of three accessory digestive organs: the liver, pancreas, and gallbladder (Figure 23.6.1). The digestive role of the liver is to produce bile and export it to the duodenum. The gallbladder primarily stores, concentrates, and releases bile. The pancreas produces pancreatic juice, which contains digestive enzymes and bicarbonate ions, and delivers it to the duodenum.
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23.8: Chemical Digestion and Absorption - A Closer Look
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As you have learned, the process of mechanical digestion is relatively simple. It involves the physical breakdown of food but does not alter its chemical makeup. Chemical digestion, on the other hand, is a complex process that reduces food into its chemical building blocks, which are then absorbed to nourish the cells of the body.


12.8.3: Managing Documentation
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As organizations begin to document their processes, it becomes an administrative task to keep track of them. As processes change and improve, it is important to know which processes are the most recent. It is also important to manage the process so that it can be easily updated! The requirement to manage process documentation has been one of the driving forces behind the creation of the document management system . A document management system stores and tracks documents and supports the following functions:
Of course, document management systems are not only used for managing business process documentation. Many other types of documents are managed in these systems, such as legal documents or design documents.


8.1.3: Water
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- Tom Buckley
- University of California, Davis
Skills to Develop
- Describe the properties of water that are critical to maintaining life
- Explain why water is an excellent solvent
- Provide examples of water’s cohesive and adhesive properties
- Discuss the role of acids, bases, and buffers in homeostasis
Why do scientists spend time looking for water on other planets? Why is water so important? It is because water is essential to life as we know it. Water is one of the more abundant molecules and the one most critical to life on Earth. Approximately 60–70 percent of the human body is made up of water. Without it, life as we know it simply would not exist.
The polarity of the water molecule and its resulting hydrogen bonding make water a unique substance with special properties that are intimately tied to the processes of life. Life originally evolved in a watery environment, and most of an organism’s cellular chemistry and metabolism occur inside the watery contents of the cell’s cytoplasm. Special properties of water are its high heat capacity and heat of vaporization, its ability to dissolve polar molecules, its cohesive and adhesive properties, and its dissociation into ions that leads to the generation of pH. Understanding these characteristics of water helps to elucidate its importance in maintaining life.
Water’s Polarity
One of water’s important properties is that it is composed of polar molecules: the hydrogen and oxygen within water molecules (H 2 O) form polar covalent bonds. While there is no net charge to a water molecule, the polarity of water creates a slightly positive charge on hydrogen and a slightly negative charge on oxygen, contributing to water’s properties of attraction. Water’s charges are generated because oxygen is more electronegative than hydrogen, making it more likely that a shared electron would be found near the oxygen nucleus than the hydrogen nucleus, thus generating the partial negative charge near the oxygen.
As a result of water’s polarity, each water molecule attracts other water molecules because of the opposite charges between water molecules, forming hydrogen bonds. Water also attracts or is attracted to other polar molecules and ions. A polar substance that interacts readily with or dissolves in water is referred to as hydrophilic (hydro- = “water”; -philic = “loving”). In contrast, non-polar molecules such as oils and fats do not interact well with water, as shown in Figure \(\PageIndex{1}\) and separate from it rather than dissolve in it, as we see in salad dressings containing oil and vinegar (an acidic water solution). These nonpolar compounds are called hydrophobic (hydro- = “water”; -phobic = “fearing”).
Water’s States: Gas, Liquid, and Solid
The formation of hydrogen bonds is an important quality of the liquid water that is crucial to life as we know it. As water molecules make hydrogen bonds with each other, water takes on some unique chemical characteristics compared to other liquids and, since living things have a high water content, understanding these chemical features is key to understanding life. In liquid water, hydrogen bonds are constantly formed and broken as the water molecules slide past each other. The breaking of these bonds is caused by the motion (kinetic energy) of the water molecules due to the heat contained in the system. When the heat is raised as water is boiled, the higher kinetic energy of the water molecules causes the hydrogen bonds to break completely and allows water molecules to escape into the air as gas (steam or water vapor). On the other hand, when the temperature of water is reduced and water freezes, the water molecules form a crystalline structure maintained by hydrogen bonding (there is not enough energy to break the hydrogen bonds) that makes ice less dense than liquid water, a phenomenon not seen in the solidification of other liquids.
Water’s lower density in its solid form is due to the way hydrogen bonds are oriented as it freezes: the water molecules are pushed farther apart compared to liquid water. With most other liquids, solidification when the temperature drops includes the lowering of kinetic energy between molecules, allowing them to pack even more tightly than in liquid form and giving the solid a greater density than the liquid.
The lower density of ice, illustrated and pictured in Figure \(\PageIndex{2}\), an anomaly, causes it to float at the surface of liquid water, such as in an iceberg or in the ice cubes in a glass of ice water. In lakes and ponds, ice will form on the surface of the water creating an insulating barrier that protects the animals and plant life in the pond from freezing. Without this layer of insulating ice, plants and animals living in the pond would freeze in the solid block of ice and could not survive. The detrimental effect of freezing on living organisms is caused by the expansion of ice relative to liquid water. The ice crystals that form upon freezing rupture the delicate membranes essential for the function of living cells, irreversibly damaging them. Cells can only survive freezing if the water in them is temporarily replaced by another liquid like glycerol.
Link to Learning
Video: Click here to see a 3-D animation of the structure of an ice lattice. (Image credit: Jane Whitney. Image created using Visual Molecular Dynamics VMD software. 2 )
Water’s High Heat Capacity
Water’s high heat capacity is a property caused by hydrogen bonding among water molecules. Water has the highest specific heat capacity of any liquids. Specific heat is defined as the amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius. For water, this amount is one calorie . It therefore takes water a long time to heat and long time to cool. In fact, the specific heat capacity of water is about five times more than that of sand. This explains why the land cools faster than the sea. Due to its high heat capacity, water is used by warm blooded animals to more evenly disperse heat in their bodies: it acts in a similar manner to a car’s cooling system, transporting heat from warm places to cool places, causing the body to maintain a more even temperature.
Water’s Heat of Vaporization
Water also has a high heat of vaporization , the amount of energy required to change one gram of a liquid substance to a gas. A considerable amount of heat energy (586 cal) is required to accomplish this change in water. This process occurs on the surface of water. As liquid water heats up, hydrogen bonding makes it difficult to separate the liquid water molecules from each other, which is required for it to enter its gaseous phase (steam). As a result, water acts as a heat sink or heat reservoir and requires much more heat to boil than does a liquid such as ethanol (grain alcohol), whose hydrogen bonding with other ethanol molecules is weaker than water’s hydrogen bonding. Eventually, as water reaches its boiling point of 100° Celsius (212° Fahrenheit), the heat is able to break the hydrogen bonds between the water molecules, and the kinetic energy (motion) between the water molecules allows them to escape from the liquid as a gas. Even when below its boiling point, water’s individual molecules acquire enough energy from other water molecules such that some surface water molecules can escape and vaporize: this process is known as evaporation .
The fact that hydrogen bonds need to be broken for water to evaporate means that a substantial amount of energy is used in the process. As the water evaporates, energy is taken up by the process, cooling the environment where the evaporation is taking place. In many living organisms, including in humans, the evaporation of sweat, which is 90 percent water, allows the organism to cool so that homeostasis of body temperature can be maintained.
Water’s Solvent Properties
Since water is a polar molecule with slightly positive and slightly negative charges, ions and polar molecules can readily dissolve in it. Therefore, water is referred to as a solvent , a substance capable of dissolving other polar molecules and ionic compounds. The charges associated with these molecules will form hydrogen bonds with water, surrounding the particle with water molecules. This is referred to as a sphere of hydration , or a hydration shell, as illustrated in Figure \(\PageIndex{3}\) and serves to keep the particles separated or dispersed in the water.
When ionic compounds are added to water, the individual ions react with the polar regions of the water molecules and their ionic bonds are disrupted in the process of dissociation . Dissociation occurs when atoms or groups of atoms break off from molecules and form ions. Consider table salt (NaCl, or sodium chloride): when NaCl crystals are added to water, the molecules of NaCl dissociate into Na + and Cl – ions, and spheres of hydration form around the ions, illustrated in Figure \(\PageIndex{3}\). The positively charged sodium ion is surrounded by the partially negative charge of the water molecule’s oxygen. The negatively charged chloride ion is surrounded by the partially positive charge of the hydrogen on the water molecule.
Water’s Cohesive and Adhesive Properties
Have you ever filled a glass of water to the very top and then slowly added a few more drops? Before it overflows, the water forms a dome-like shape above the rim of the glass. This water can stay above the glass because of the property of cohesion . In cohesion, water molecules are attracted to each other (because of hydrogen bonding), keeping the molecules together at the liquid-gas (water-air) interface, although there is no more room in the glass.
Cohesion allows for the development of surface tension , the capacity of a substance to withstand being ruptured when placed under tension or stress. This is also why water forms droplets when placed on a dry surface rather than being flattened out by gravity. When a small scrap of paper is placed onto the droplet of water, the paper floats on top of the water droplet even though paper is denser (heavier) than the water. Cohesion and surface tension keep the hydrogen bonds of water molecules intact and support the item floating on the top. It’s even possible to “float” a needle on top of a glass of water if it is placed gently without breaking the surface tension, as shown in Figure \(\PageIndex{4}\).
These cohesive forces are related to water’s property of adhesion , or the attraction between water molecules and other molecules. This attraction is sometimes stronger than water’s cohesive forces, especially when the water is exposed to charged surfaces such as those found on the inside of thin glass tubes known as capillary tubes. Adhesion is observed when water “climbs” up the tube placed in a glass of water: notice that the water appears to be higher on the sides of the tube than in the middle. This is because the water molecules are attracted to the charged glass walls of the capillary more than they are to each other and therefore adhere to it. This type of adhesion is called capillary action , and is illustrated in Figure \(\PageIndex{5}\).
Why are cohesive and adhesive forces important for life? Cohesive and adhesive forces are important for the transport of water from the roots to the leaves in plants. These forces create a “pull” on the water column. This pull results from the tendency of water molecules being evaporated on the surface of the plant to stay connected to water molecules below them, and so they are pulled along. Plants use this natural phenomenon to help transport water from their roots to their leaves. Without these properties of water, plants would be unable to receive the water and the dissolved minerals they require. In another example, insects such as the water strider, shown in Figure \(\PageIndex{6}\), use the surface tension of water to stay afloat on the surface layer of water and even mate there.
pH, Buffers, Acids, and Bases
The pH of a solution indicates its acidity or alkalinity.
litmus or pH paper, filter paper that has been treated with a natural water-soluble dye so it can be used as a pH indicator, to test how much acid (acidity) or base (alkalinity) exists in a solution. You might have even used some to test whether the water in a swimming pool is properly treated. In both cases, the pH test measures the concentration of hydrogen ions in a given solution.
Hydrogen ions are spontaneously generated in pure water by the dissociation (ionization) of a small percentage of water molecules into equal numbers of hydrogen (H + ) ions and hydroxide (OH - ) ions. While the hydroxide ions are kept in solution by their hydrogen bonding with other water molecules, the hydrogen ions, consisting of naked protons, are immediately attracted to un-ionized water molecules, forming hydronium ions (H 3 0 + ). Still, by convention, scientists refer to hydrogen ions and their concentration as if they were free in this state in liquid water.
The concentration of hydrogen ions dissociating from pure water is 1 × 10 -7 moles H + ions per liter of water. Moles (mol) are a way to express the amount of a substance (which can be atoms, molecules, ions, etc), with one mole being equal to 6.02 x 10 23 particles of the substance. Therefore, 1 mole of water is equal to 6.02 x 10 23 water molecules. The pH is calculated as the negative of the base 10 logarithm of this concentration. The log10 of 1 × 10 -7 is -7.0, and the negative of this number (indicated by the “p” of “pH”) yields a pH of 7.0, which is also known as neutral pH. The pH inside of human cells and blood are examples of two areas of the body where near-neutral pH is maintained.
Non-neutral pH readings result from dissolving acids or bases in water. Using the negative logarithm to generate positive integers, high concentrations of hydrogen ions yield a low pH number, whereas low levels of hydrogen ions result in a high pH. An acid is a substance that increases the concentration of hydrogen ions (H + ) in a solution, usually by having one of its hydrogen atoms dissociate. A base provides either hydroxide ions (OH – ) or other negatively charged ions that combine with hydrogen ions, reducing their concentration in the solution and thereby raising the pH. In cases where the base releases hydroxide ions, these ions bind to free hydrogen ions, generating new water molecules.
The stronger the acid, the more readily it donates H + . For example, hydrochloric acid (HCl) completely dissociates into hydrogen and chloride ions and is highly acidic, whereas the acids in tomato juice or vinegar do not completely dissociate and are considered weak acids. Conversely, strong bases are those substances that readily donate OH – or take up hydrogen ions. Sodium hydroxide (NaOH) and many household cleaners are highly alkaline and give up OH – rapidly when placed in water, thereby raising the pH. An example of a weak basic solution is seawater, which has a pH near 8.0, close enough to neutral pH that marine organisms adapted to this saline environment are able to thrive in it.
The pH scale is, as previously mentioned, an inverse logarithm and ranges from 0 to 14 (Figure \(\PageIndex{7}\)). Anything below 7.0 (ranging from 0.0 to 6.9) is acidic, and anything above 7.0 (from 7.1 to 14.0) is alkaline. Extremes in pH in either direction from 7.0 are usually considered inhospitable to life. The pH inside cells (6.8) and the pH in the blood (7.4) are both very close to neutral. However, the environment in the stomach is highly acidic, with a pH of 1 to 2. So how do the cells of the stomach survive in such an acidic environment? How do they homeostatically maintain the near neutral pH inside them? The answer is that they cannot do it and are constantly dying. New stomach cells are constantly produced to replace dead ones, which are digested by the stomach acids. It is estimated that the lining of the human stomach is completely replaced every seven to ten days.
Link to Learning
Watch this video for a straightforward explanation of pH and its logarithmic scale.
So how can organisms whose bodies require a near-neutral pH ingest acidic and basic substances (a human drinking orange juice, for example) and survive? Buffers are the key. Buffers readily absorb excess H + or OH – , keeping the pH of the body carefully maintained in the narrow range required for survival. Maintaining a constant blood pH is critical to a person’s well-being. The buffer maintaining the pH of human blood involves carbonic acid (H 2 CO 3 ), bicarbonate ion (HCO 3 – ), and carbon dioxide (CO 2 ). When bicarbonate ions combine with free hydrogen ions and become carbonic acid, hydrogen ions are removed, moderating pH changes. Similarly, as shown in Figure \(\PageIndex{8}\), excess carbonic acid can be converted to carbon dioxide gas and exhaled through the lungs. This prevents too many free hydrogen ions from building up in the blood and dangerously reducing the blood’s pH. Likewise, if too much OH – is introduced into the system, carbonic acid will combine with it to create bicarbonate, lowering the pH. Without this buffer system, the body’s pH would fluctuate enough to put survival in jeopardy.
Other examples of buffers are antacids used to combat excess stomach acid. Many of these over-the-counter medications work in the same way as blood buffers, usually with at least one ion capable of absorbing hydrogen and moderating pH, bringing relief to those that suffer “heartburn” after eating. The unique properties of water that contribute to this capacity to balance pH—as well as water’s other characteristics—are essential to sustaining life on Earth.
Link to Learning
To learn more about water. Visit the U.S. Geological Survey Water Science for Schools All About Water! website.
Summary
Water has many properties that are critical to maintaining life. It is a polar molecule, allowing for the formation of hydrogen bonds. Hydrogen bonds allow ions and other polar molecules to dissolve in water. Therefore, water is an excellent solvent. The hydrogen bonds between water molecules cause the water to have a high heat capacity, meaning it takes a lot of added heat to raise its temperature. As the temperature rises, the hydrogen bonds between water continually break and form anew. This allows for the overall temperature to remain stable, although energy is added to the system. Water also exhibits a high heat of vaporization, which is key to how organisms cool themselves by the evaporation of sweat. Water’s cohesive forces allow for the property of surface tension, whereas its adhesive properties are seen as water rises inside capillary tubes. The pH value is a measure of hydrogen ion concentration in a solution and is one of many chemical characteristics that is highly regulated in living organisms through homeostasis. Acids and bases can change pH values, but buffers tend to moderate the changes they cause. These properties of water are intimately connected to the biochemical and physical processes performed by living organisms, and life would be very different if these properties were altered, if it could exist at all.
Footnotes
- 1 W. Humphrey W., A. Dalke, and K. Schulten, “VMD—Visual Molecular Dynamics,” Journal of Molecular Graphics 14 (1996): 33-38.
- 2 W. Humphrey W., A. Dalke, and K. Schulten, “VMD—Visual Molecular Dynamics,” Journal of Molecular Graphics 14 (1996): 33-38.
Glossary
- acid
- molecule that donates hydrogen ions and increases the concentration of hydrogen ions in a solution
- adhesion
- attraction between water molecules and other molecules
- base
- molecule that donates hydroxide ions or otherwise binds excess hydrogen ions and decreases the concentration of hydrogen ions in a solution
- buffer
- substance that prevents a change in pH by absorbing or releasing hydrogen or hydroxide ions
- calorie
- amount of heat required to change the temperature of one gram of water by one degree Celsius
- capillary action
- occurs because water molecules are attracted to charges on the inner surfaces of narrow tubular structures such as glass tubes, drawing the water molecules to the sides of the tubes
- cohesion
- intermolecular forces between water molecules caused by the polar nature of water; responsible for surface tension
- dissociation
- release of an ion from a molecule such that the original molecule now consists of an ion and the charged remains of the original, such as when water dissociates into H + and OH -
- evaporation
- separation of individual molecules from the surface of a body of water, leaves of a plant, or the skin of an organism
- heat of vaporization of water
- high amount of energy required for liquid water to turn into water vapor
- hydrophilic
- describes ions or polar molecules that interact well with other polar molecules such as water
- hydrophobic
- describes uncharged non-polar molecules that do not interact well with polar molecules such as water
- litmus paper
- (also, pH paper) filter paper that has been treated with a natural water-soluble dye that changes its color as the pH of the environment changes so it can be used as a pH indicator
- pH paper
- see litmus paper
- pH scale
- scale ranging from zero to 14 that is inversely proportional to the concentration of hydrogen ions in a solution
- solvent
- substance capable of dissolving another substance
- specific heat capacity
- the amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius
- sphere of hydration
- when a polar water molecule surrounds charged or polar molecules thus keeping them dissolved and in solution
- surface tension
- tension at the surface of a body of liquid that prevents the molecules from separating; created by the attractive cohesive forces between the molecules of the liquid


12.E: Distribution Free Tests (Exercises)
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General Questions
Q1
For the following data, how many ways could the data be arranged (including the original arrangement) so that the advantage of the Experimental Group mean over the Control Group mean is as large or larger then the original arrangement?
| Experimental | Control |
|---|---|
| 5 | 1 |
| 10 | 2 |
| 15 | 3 |
| 16 | 4 |
| 17 | 9 |
Q2
For the data in Problem 1, how many ways can the data be rearranged?
Q3
What is the one-tailed probability for a test of the difference?
Q4
For the following data, how many ways can the data be rearranged?
| T1 | T2 | Control |
|---|---|---|
| 7 | 14 | 0 |
| 8 | 19 | 2 |
| 11 | 21 | 5 |
Q5
In general, are rank randomization tests or randomization tests more powerful?
Q6
What is the advantage of rank randomization tests over randomization tests?
Q7
Test whether the differences among conditions for the data in Problem 1 is significant (one tailed) at the \(0.01\) level using a rank randomization test.
Questions from Case Studies
The following question uses data from the SAT and GPA case study.
Q8
Compute Spearman's \(ρ\) for the relationship between UGPA and SAT.
The following question uses data from the Stereograms case study.
Q9
Test the difference in central tendency between the two conditions using a rank-randomization test (with the normal approximation) with a one-tailed test. Give the \(Z\) and the \(p\).
The following question uses data from the Smiles and Leniency case study.
Q10
Test the difference in central tendency between the four conditions using a rank-randomization test (with the normal approximation). Give the Chi Square and the \(p\).


10.6: Hypothesis Testing for Two Means and Two Proportions (Worksheet)
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Name: ______________________________
Section: _____________________________
Student ID#:__________________________
Work in groups on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help.
Student Learning Outcomes
- The student will select the appropriate distributions to use in each case.
- The student will conduct hypothesis tests and interpret the results.
Supplies:
- the business section from two consecutive days’ newspapers
- three small packages of M&Ms®
- five small packages of Reese's Pieces®
Increasing Stocks Survey
Look at yesterday’s newspaper business section. Conduct a hypothesis test to determine if the proportion of New York Stock Exchange (NYSE) stocks that increased is greater than the proportion of NASDAQ stocks that increased. As randomly as possible, choose 40 NYSE stocks, and 32 NASDAQ stocks and complete the following statements.- \(H_{0}\): _________
- \(H_{a}\) : _________
- In words, define the random variable.
- The distribution to use for the test is _____________.
- Calculate the test statistic using your data.
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Draw a graph and label it appropriately. Shade the actual level of significance.
- Graph:
- Calculate the \(p\text{-value}\).
- Do you reject or not reject the null hypothesis? Why?
- Write a clear conclusion using a complete sentence.
Decreasing Stocks Survey
Randomly pick eight stocks from the newspaper. Using two consecutive days’ business sections, test whether the stocks went down, on average, for the second day.- \(H_{0}\): ________
- \(H_{a}\) : ________
- In words, define the random variable.
- The distribution to use for the test is _____________.
- Calculate the test statistic using your data.
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Draw a graph and label it appropriately. Shade the actual level of significance.
- Graph:
- Calculate the \(p\text{-value}\):
- Do you reject or not reject the null hypothesis? Why?
- Write a clear conclusion using a complete sentence.
Candy Survey
Buy three small packages of M&Ms and five small packages of Reese's Pieces (same net weight as the M&Ms). Test whether or not the mean number of candy pieces per package is the same for the two brands.
- \(H_{0}\): ________
- \(H_{a}\): ________
- In words, define the random variable.
- What distribution should be used for this test?
- Calculate the test statistic using your data.
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Draw a graph and label it appropriately. Shade the actual level of significance.
- Graph:
- Calculate the \(p\text{-value}\).
- Do you reject or not reject the null hypothesis? Why?
- Write a clear conclusion using a complete sentence.
Shoe Survey
Test whether women have, on average, more pairs of shoes than men. Include all forms of sneakers, shoes, sandals, and boots. Use your class as the sample.
- \(H_{0}\): ________
- \(H_{a}\): ________
- In words, define the random variable.
- The distribution to use for the test is ________________.
- Calculate the test statistic using your data.
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Draw a graph and label it appropriately. Shade the actual level of significance.
- Graph:
- Calculate the \(p\text{-value}\).
- Do you reject or not reject the null hypothesis? Why?
- Write a clear conclusion using a complete sentence.


18.1: MTI—Its Importance Now and In the Future
- What do we mean by the management of technology and innovation (MTI), and why is it crucial?
Management of technology and innovation is critical to the organization. Because of innovations and new technologies, we have historically seen the emergence of innovative organizational structures and new ways of performing work. For example, the Industrial Revolution ushered in the functional structure for organizations. As business moved from small craft businesses like blacksmiths to railroads, there was a need to introduce a more complex business structure. Today, we see the innovations in information technology changing structures to more network based with people being able to work remotely. The changes in structure are innovations in the technology of how work is accomplished; the innovations brought on by the invention of new products influence the technology we use and how we use it.
Technology can be defined in a number of ways. The basic purpose of a system (such as an organization) is to convert inputs into outputs. Therefore, we will define organizational technology as the processes within the organization that help to convert inputs into outputs as well as the supporting evaluation and control mechanisms. The management of technology involves the planning, implementation, evaluation, and control of the organization’s resources and capabilities in order to create value and competitive advantage. This involves managing:
- Technology strategy—the logic of how technology will be used and what role technology will have in the organization. For example, will innovation (first-to-market strategies dominate) be the focus, or will the firm want to do things better to obtain market share and value (let others take the initial risks)?
- Technology forecasting—the use of tools to study the environment for potential technological changes that can both positively and negatively affect the firm’s value proposition. Digitization of a variety of products such as watches and cameras provided great opportunities for some firms and caused others to go bankrupt. Forecasting (or at least keeping an eye on the changes in technology) is very important in the management of technology.
- Technology road-mapping—the process of taking an innovation or technology and trying to build more value by looking for ways to use technology in different markets and places.
- Technology project portfolio—the use of portfolio techniques in the development and use of technology enhances the potential value of technologies being developed and the technologies that are currently part of a firm’s portfolio. Disney was a leading producer of animated films. However, Disney did not stop there—the portfolio of characters in the films are now marketed as products and displayed in Disney theme parks, and Disney very carefully manages the availability of the animated films.
Innovation activities are an important subset of technology activities. Innovation includes “newness” in the development and used of products and/or processes within a firm and within an industry. Invention, new product development, and process-improvement methods are all examples of innovation. Management of innovation includes both change management and managing organizational processes that encourage innovation. The management of innovation is more than just planning new products, services, brand extensions, or technology inventions—it is about imagining, mobilizing, and competing in new ways. For the organization, innovation management involves setting up systems and processes that allow newness that adds value to emerge. Some firms, like Google and 3M, give some employees time during the workweek to work on their own ideas with the hope of sparking new ideas that will add value. Google News and 3M Post-it Notes are products that emerged from this practice. In order to manage innovation processes successfully, the firm must undertake several activities (these can involve the study of technologies currently in use).
- Casting a wide net while trying to keep up with potential changes in the firm, the market, the competition, etc. is crucial. Eastman Kodak was the dominant U.S. camera manufacturer. On several occasions in their history they missed opportunities to take advantage of innovations in their product line—they did not cast their net out. Land, the founder of Polaroid, went to Kodak with his invention of instant photographs—Kodak said no. Kodak did not see the telephone as a potential competitor until it was too late. Kodak was especially vulnerable because the firm was a late entrant into the digital camera market. As a result of failure to cast a wide net in keeping up with trends and innovations, Kodak went bankrupt.
- Creating newness with existing products can expand the portfolio of value of a product. 3M has done this with all kinds of tape and with different formats and forms of Post-it Notes. Asking “how else can the product be altered or used?” is critical to developing platforms of products.
- Creating a culture open to newness is critical to cultivating ideas. If the leadership of the firm is open to ideas from all over the organization, then the firm will be more innovative. Some large firms such as Texas Instruments encourage employees to start new businesses if TI does not want to keep a product in house. Often, TI is the first investor and customer of these small firms.
- Communicating knowledge throughout the firm is important. This knowledge can be positive and negative at first glance. For Post-it Notes, the glue used emerged from the laboratory efforts to create a stronger glue to compete with Elmer’s Super Glue. Obviously, the outcome did not meet the original goal, but the communication of the new formula’s characteristics—tacky and leaves no residue—triggered other usage.
- Changing with courage is necessary if a firm is going to manage innovation and stay competitive. Too often firms get comfortable with where they are, narrow their focus in studying the environment, and focus on building strength in their current market. This leads to strategic inertia—not innovating and losing customers and market share to more innovative companies. Just as Kodak failed to change, so did IBM—famously, the CEO of IBM was quoted as saying “who wants a computer on their desk?” as IBM continued manufacturing mainframes while desktops and then laptops were emerging.
MANAGING CHANGE
E-Hubs Integrate Global Commerce
Thanks to the wonders of technological advancement, global electronic trading now goes far beyond the Internet retailing and trading that we are all familiar with. Special websites known as trading hubs, or eMarketplaces, facilitate electronic commerce between businesses in specific industries such as automotive manufacturing, retailing, telecom provisioning, aerospace, financial products and services, and more. Virtually all Forex (foreign exchange) is done via trading hubs that provide an open market for trading of a variety of currencies. Because there are a large number of trades involving currencies, the price is discoverable and there is transparency in the market. By contrast, Bitcoin is mainly traded in smaller quantities, and there are often large discrepancies between prices for the cryptocurrency in different exchanges.
The trading hub functions as a means of integrating the electronic collaboration of business services. Each hub provides standard formats for the electronic trading of documents used in a particular industry, as well as an array of services to sustain e-commerce between businesses in that industry. Services include demand forecasting, inventory management, partner directories, and transaction-settlement services. And the payoff is significant—lowered costs, decreased inventory levels, and shorter time to market—resulting in bigger profits and enhanced competitiveness. For example, large-scale manufacturing procurement can amount to billions of dollars. Changing to “just-in-time purchasing” on the e-hub can save a considerable percentage of these costs.
Electronic trading across a hub can range from the collaborative integration of individual business processes to auctions and exchanges of goods (electronic barter). Global content management is an essential factor in promoting electronic trading agreements on the hub. A globally consistent view of the “content” of the hub must be available to all. Each participating company handles its own content, and applications such as content managers keep a continuously updated master catalog of the inventories of all members of the hub. The transaction manager application automates trading arrangements between companies, allowing the hub to provide aggregation and settlement services.
Ultimately, trading hubs for numerous industries could be linked together in a global e-commerce web—an inclusive “hub of all hubs . ” One creative thinker puts it this way: “The traditional linear, one step at a time, supply chain is dead. It will be replaced by parallel, asynchronous, real-time marketplace decision-making. Take manufacturing capacity as an example. Enterprises can bid their excess production capacity on the world e-commerce hub. Offers to buy capacity trigger requests from the seller for parts bids to suppliers who in turn put out requests to other suppliers, and this whole process will all converge in a matter of minutes.”
Sources: “Asian Companies Count Losses—Hatch Ways to Cope with Weak Dollar,” Reuters , https://www.reuters.com , January 24, 2018; Rob Verger, “This Is What Determines the Price of Bitcoin,” Popular Science , https://www.popsci.com , January 22, 2018; Bhavan Jaipragas, “Alibaba’s Electronic Trading Hub to Help Small and Medium-sized Enterprises Goes Live in Malaysia,” This Week in Asia , http://www.scmp.com , November 3, 2017.
- How do companies benefit from participating in an electronic trading hub?
- What impact does electronic trading have on the global economy?
There are six critical areas that affect society and business and thus require firms to practice good management of technology and innovation. Each of these must be managed for value to be created and captured: 1
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Management of Human Resources. Work environment (tools and structures) are much different today than they were at the turn of the millennium. For example, the iPhone was first introduced in 2007. Cell phone technology in the year 2000 was not for everyone—most people still had landline telephones. The introduction of cell phone technology and its use in business has made many employees feel like they are on 24-hour call. Because workers tend to carry their phones everywhere, they are available to be called, texted, or e-mailed.
Providing learning opportunities (whether online or traditional training and development) has become a more important part of human resources management—employees need to be given time to adjust to the introduction of new ways of working, new software, etc. For example, it is the rare 45-year-old manager today that owned or used a laptop computer before graduating college.
- Cooperative Model Expansion. The more rapidly innovation occurs, the more rapidly technology occurs within firms, within industries, and within economies. These changes require that cooperatives be developed. These cooperatives can take a variety of forms, both internal and external to the firm. We will discuss internal and external MTI as well as entrepreneurial MTI.
- Internationalization. There is much more internationalization of products and markets. Sometimes, the innovations spread in ways that were not predicted. For example, GE wanted to develop a portable MRI machine to be used in less-developed countries. The machine would be portable and would use a laptop interface to send images for diagnoses. It was successful developed and a plant was built overseas, and then GE discovered there were markets in more-developed economies that they had not considered. For example, large-animal veterinarians wanted to use the machines on farms and ranches. Finding the best markets and the best production options has become an important part of MTI.
- Issues around Environmental Concerns. Environmental concerns can be important throughout the whole life cycle of a product. From development to manufacturing to usage to disposal, are all concerns for MTI. For example, energy production is a cause of great concern. The use of fossil fuels such as coal, oil, and natural gas have impacted carbon levels in the atmosphere. Nuclear power does not have that impact, but accidents at such facilities can be catastrophic. Use of wind, water, waves, and sunlight to produce energy does not lead to carbon emissions, but there are other environmental concerns. Building large dams such as Hoover Dam in the United States is much more difficult now because society is much more aware of the changes in the ecosystem such large projects cause.
- Growth of Service Industries. As economies become more knowledge and information based, service industries will continue to grow. The services provided by Internet suppliers, specialists in network security, etc. will influence how business will grow for the foreseeable future—especially in developing economies. The emergence of a more knowledge- and information-based global economy means that services will become more critical and service industries will continue to grow at a faster pace than product-based industries. 2
- Use of Intellectual Property Rights (IPR) as a Strategic Resource. Because many new products and processes are based on intellectual property rights (patents, copyrights, and trademarks), it is crucial that organizations manage their IPR as a valuable asset. This requires value articulation through value transference, translation, and transportation. 3 For example, Dolby Laboratories patented innovative noise-reduction technology that was translated to a stereo film sound technique that was patent protected to transportation to new patents protecting the “analog world.” As a result, Dolby enjoyed long-term growth from its innovation and over 80 percent of its revenues came from licensing the technology rather than producing competing products.
Organizations have to be flexible in the management of technology and innovation. Acer, in the opening case, has used a variety of methods to acquire new technology and to innovate and expand its platforms. When Acer started out, the management realized that being a domestic company in Taiwan was very limiting, so they cast their net widely. They originally used internal R&D to grow. Then they expanded their markets and their product lines through mergers and acquisitions. They have increased their product offerings as the laptop market has matured. They are now using services platforms to continue their expansion and growth.
- How are the management of technology and the management of innovation similar? How are they different?
- How can firms create value through good management of technology and innovation?
- How has Acer managed its technology and innovation processes?


27.1: Anatomy and Physiology of the Male Reproductive System
Learning Objectives
- 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 (Figure \(\PageIndex{1}\)) is to produce sperm and transfer them to the female reproductive tract. 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.
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 \(\PageIndex{1}\)). 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 \(\PageIndex{2}\)). 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 raphae.
 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 \(\PageIndex{2}\)). They are surrounded by two distinct layers of protective connective tissue (Figure \(\PageIndex{3}\)). 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. 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.
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 . Sertoli cells are a type of supporting cell called a sustentacular cell, or sustenocyte, that are typically found in epithelial tissue.  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 (see Figure \(\PageIndex{3}\)). 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 (Figure \(\PageIndex{4}\)). Because these cells are diploid (2 n ), they each have a complete copy of the father’s genetic material, or 46 chromosomes. However, 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.
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. Sperm have a distinctive head, mid-piece, and tail region (Figure \(\PageIndex{5}\)). The head of the sperm contains the extremely compact haploid nucleus with very little cytoplasm. 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 \(\PageIndex{3}\)). 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. As they are moved along the length of the epididymis, the sperm further mature and acquire the ability to move under their own power. Once inside the female reproductive tract, they will use this ability to move independently toward the unfertilized egg. 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 \(\PageIndex{1}\) and Figure \(\PageIndex{2}\)). 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.
Vasectomy
Watch this video to learn about a vasectomy. As described in this video, a vasectomy is 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?
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.
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 \(\PageIndex{1}\)). 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.
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 \(\PageIndex{1}\), 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.
  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.
 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 \(\PageIndex{1}\)). 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.   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 intricate interplay between the endocrine system and the reproductive system is shown in Figure \(\PageIndex{7}\).
Figure \(\PageIndex{7}\): Regulation of Testosterone Production. The hypothalamus and pituitary gland regulate the production of testosterone and the cells that assist in spermatogenesis. GnRH activates the anterior pituitary to produce LH and FSH, which in turn stimulate Leydig cells and Sertoli cells, respectively. The system is a negative feedback loop because the end products of the pathway, testosterone and inhibin, interact with the activity of GnRH to inhibit their own production.
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 B 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.
A negative feedback loop predominantly controls the synthesis and secretion of both FSH and LH. Low blood concentrations of testosterone stimulate the hypothalamic release of GnRH. GnRH then stimulates the anterior pituitary to secrete LH into the bloodstream. In the testis, LH binds to LH receptors on Leydig cells and stimulates the release of testosterone. When concentrations of testosterone in the blood reach a critical threshold, testosterone itself will bind to androgen receptors on both the hypothalamus and the anterior pituitary, inhibiting the synthesis and secretion of GnRH and LH, respectively. When the blood concentrations of testosterone once again decline, testosterone no longer interacts with the receptors to the same degree and GnRH and LH are once again secreted, stimulating more testosterone production. This same process occurs with FSH and inhibin to control spermatogenesis.
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.
Chapter 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 the 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 with a negative feedback loop.
Interactive Link Questions
Q. Watch this video to learn about vasectomy. As described in this video, a vasectomy is 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: Sperm remain in the epididymis until they degenerate.
Q. Watch this video to explore the structures of the male reproductive system and the path of sperm that starts in the testes and ends as the sperm leave the penis through the urethra. Where are sperm deposited after they leave the ejaculatory duct?
Answer: Sperm enter the prostate.
Review Questions
Q. What are male gametes called?
A. ova
B. sperm
C. testes
D. testosterone
Answer: B
Q. Leydig cells ________.
A. secrete testosterone
B. activate the sperm flagellum
C. support spermatogenesis
D. secrete seminal fluid
Answer: A
Q. Which hypothalamic hormone contributes to the regulation of the male reproductive system?
A. luteinizing hormone
B. gonadotropin-releasing hormone
C. follicle-stimulating hormone
D. androgens
Answer: B
Q. What is the function of the epididymis?
A. sperm maturation and storage
B. produces the bulk of seminal fluid
C. provides nitric oxide needed for erections
D. spermatogenesis
Answer: A
Q. Spermatogenesis takes place in the ________.
A. prostate gland
B. glans penis
C. seminiferous tubules
D. ejaculatory duct
Answer: C
Critical Thinking Questions
Q. Briefly explain why mature gametes carry only one set of chromosomes.
A. 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 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?
A. Unlike somatic cells, sperm are haploid. They also have very little cytoplasm.  They are motile because of their tail, a structure containing a flagellum, which is specialized for movement.
Q. What do each of the three male accessory glands contribute to the semen?
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.
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.
Q. While anabolic steroids (synthetic testosterone) bulk up muscles, they can also affect testosterone production in the testis. Using what you know about negative feedback, describe what would happen to testosterone production in the testis if a male takes large amounts of synthetic testosterone.
A. Testosterone production by the body would be reduced if a male were taking anabolic steroids. This is because the hypothalamus responds to rising testosterone levels by reducing its secretion of GnRH, which would in turn reduce the anterior pituitary’s release of LH, finally reducing the manufacture of testosterone in the testes.
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