9.4: Argumentative Thesis Statements
- Recognize an argumentative thesis
A strong, argumentative thesis statement should take a stance about an issue. It should explain the basics of your argument and help your reader to know what to expect in your essay.
This video reviews the necessary components of a thesis statement and walks through some examples.
You can view the transcript for “Purdue OWL: Thesis Statements” here (opens in new window) .
Key Features of Argumentative Thesis Statements
Below are some of the key features of an argumentative thesis statement. An argumentative thesis is debatable, assertive, reasonable, evidence-based, and focused.
Debatable
An argumentative thesis must make a claim about which reasonable people can disagree. Statements of fact or areas of general agreement cannot be argumentative theses because few people disagree about them. Let’s take a look at an example:
- BAD: Junk food is bad for your health.
This is not a debatable thesis. Most people would agree that junk food is bad for your health. A debatable thesis would be:
- GOOD: Because junk food is bad for your health, the size of sodas offered at fast-food restaurants should be regulated by the federal government.
Reasonable people could agree or disagree with the statement.
Assertive
An argumentative thesis takes a position, asserting the writer’s stance. Questions, vague statements, or quotations from others are not argumentative theses because they do not assert the writer’s viewpoint. Let’s take a look at an example:
- BAD: Federal immigration law is a tough issue about which many people disagree.
This is not an arguable thesis because it does not assert a position.
- GOOD: Federal immigration enforcement law needs to be overhauled because it puts undue constraints on state and local police.
This is an argumentative thesis because it asserts a position that immigration enforcement law needs to be changed.
Reasonable
An argumentative thesis must make a claim that is logical and possible. Claims that are outrageous or impossible are not argumentative theses. Let’s take a look at an example:
- BAD: City council members are dishonest and should be thrown in jail.
This is not an argumentative thesis. City council members’ ineffectiveness is not a reason to send them to jail.
- GOOD: City council members should be term-limited to prevent one group or party from maintaining control indefinitely.
This is an arguable thesis because term limits are possible, and shared political control is a reasonable goal.
Evidence-Based
An argumentative thesis must be able to be supported by evidence. Claims that presuppose value systems, morals, or religious beliefs cannot be supported with evidence and therefore are not argumentative theses.
This is not an argumentative thesis because its support rests on religious beliefs or values rather than evidence.
- GOOD: Rehabilitation programs for individuals serving life sentences should be funded because these programs reduce violence within prisons.
This is an argumentative thesis because evidence such as case studies and statistics can be used to support it.
Focused
An argumentative thesis must be focused and narrow. A focused, narrow claim is clearer, more able to be supported with evidence, and more persuasive than a broad, general claim. Let’s take a look at an example:
- BAD: The federal government should overhaul the U.S. tax code.
This is not an effective argumentative thesis because it is too general (What part of the government? Which tax codes? What sections of those tax codes?) and would require an overwhelming amount of evidence to be fully supported.
- GOOD: The U.S. House of Representatives should vote to repeal the federal estate tax because the revenue generated by that tax is negligible.
This is an effective argumentative thesis because it identifies a specific actor and action and can be fully supported with evidence about the amount of revenue the estate tax generates.
In the practice exercises below, you will use this information from your reading to see if you can recognize and evaluate argumentative thesis statements. Keep in mind that a sound argumentative thesis should be debatable, assertive, reasonable, evidence-based, and focused.
Contributors and Attributions
- Argumentative Thesis Statements. Provided by : University of Mississippi. License : CC BY: Attribution
- Argumentative Thesis Activity. Provided by : Excelsior College. Located at : http://owl.excelsior.edu/argument-and-critical-thinking/argumentative-thesis/argumentative-thesis-activity/ . License : CC BY: Attribution
- Purdue OWL: Thesis Statements. Provided by : OWLPurdue. Located at : https://www.youtube.com/watch?v=LKXkemYldmw . License : Other . License Terms : Standard YouTube License


17: Image Analysis- What You See
Figure \(17.1\) On the left is a carved medallion, found at Amaravati in a Buddhist shrine that dates from the later years BCE to the early CE. On the right, the individual images in the carving are outlined and numbered, explaining the narrative sequence and showing the audience how to “read” the medallion. Together, the two serve as an early example of visual rhetoric. (credit: “Chaddanta Jataja Amaravati” by Vidya Dehejia/Wikimedia Commons, CC0)
Chapter Outline
Introduction
Many people spend a substantial portion of their time watching and assessing images—including photographs, memes, graphs, and videos—via television, streaming services, and social media platforms. Even the college curriculum is as much visual as it is verbal, including as it does Internet research, computer graphics, and PowerPoint presentations. These forms of media might be relatively new, but people have been creating and consuming images for millennia, as you can see in Figure \(17.1\). An important part of human development consists of making images, enjoying them, and talking about them.
Formerly, visual texts were created exclusively by painters, photographers, and others generally designated as artists. Today, given the proliferation of technologies that enable the easy capture and manipulation of images, such visual texts are created by a multitude of authors. In this chapter, terms for these image creators—artist, author, composer, creator—are used interchangeably.
Chapter 17 examines the elements of visual literacy and analysis most likely to complement the textual literacy emphasized in first-year writing classes and addressed in Print or Textual Analysis: What You Read. A critical understanding of visual texts is key to helping you both as a consumer of the frequent images you encounter in reading and viewing and as a producer who incorporates images into your own writing, as addressed in Multimodal and Online Writing: Creative Interaction between Text and Image. Overall, this chapter provides a solid basis for understanding visual rhetoric and communicating about it in various situations. After study and practice, you will be able to do so while drawing on your own cultural context, background, and experience and considering your audience, purpose, and rhetorical context.


22.2: Bacterial Infections of the Respiratory Tract
- Identify the most common bacteria that can cause infections of the upper and lower respiratory tract
- Compare the major characteristics of specific bacterial diseases of the respiratory tract
The respiratory tract can be infected by a variety of bacteria, both gram positive and gram negative. Although the diseases that they cause may range from mild to severe, in most cases, the microbes remain localized within the respiratory system. Fortunately, most of these infections also respond well to antibiotic therapy.
Streptococcal Infections
A common upper respiratory infection, streptococcal pharyngitis (strep throat) is caused by Streptococcus pyogenes . This gram-positive bacterium appears as chains of cocci, as seen in Figure \(\PageIndex{1}\). Rebecca Lancefieldserologically classified streptococci in the 1930s using carbohydrate antigens from the bacterial cell walls. S. pyogenes is the sole member of the Lancefield group A streptococci and is often referred to as GAS, or group A strep.
Similar to streptococcal infections of the skin, the mucosal membranes of the pharynx are damaged by the release of a variety of exoenzymes and exotoxins by this extracellular pathogen. Many strains of S. pyogenes can degrade connective tissues by using hyaluronidase, collagenase and streptokinase. Streptokinase activates plasmin, which leads to degradation of fibrin and, in turn, dissolution of blood clots, which assists in the spread of the pathogen. Released toxins include streptolysins that can destroy red and white blood cells. The classic signs of streptococcal pharyngitis are a fever higher than 38 °C (100.4 °F); intense pharyngeal pain; erythema associated with pharyngeal inflammation; and swollen, dark-red palatine tonsils, often dotted with patches of pus; and petechiae (microcapillary hemorrhages) on the soft or hard palate (roof of the mouth) (Figure \(\PageIndex{2}\)). The submandibular lymph nodes beneath the angle of the jaw are also often swollen during strep throat.
Some strains of group A streptococci produce erythrogenic toxin. This exotoxin is encoded by a temperate bacteriophage (bacterial virus) and is an example of phage conversion (see The Viral Life Cycle ). The toxin attacks the plasma membranes of capillary endothelial cells and leads to scarlet fever (or scarlatina), a disseminated fine red rash on the skin, and strawberry tongue, a red rash on the tongue (Figure \(\PageIndex{2}\)). Severe cases may even lead to streptococcal toxic shock syndrome (STSS), which results from massive superantigen production that leads to septic shock and death.
S. pyogenes can be easily spread by direct contact or droplet transmission through coughing and sneezing. The disease can be diagnosed quickly using a rapid enzyme immunoassay for the group A antigen. However, due to a significant rate of false-negative results (up to 30% 1 ), culture identification is still the gold standard to confirm pharyngitis due to S. pyogenes . S. pyogenes can be identified as a catalase-negative, beta hemolytic bacterium that is susceptible to 0.04 units of bacitracin. Antibiotic resistance is limited for this bacterium, so most β-lactams remain effective; oral amoxicillin and intramuscular penicillin G are those most commonly prescribed.
Sequelae of S. pyogenes Infections
One reason strep throat infections are aggressively treated with antibiotics is because they can lead to serious sequelae, later clinical consequences of a primary infection. It is estimated that 1%–3% of untreated S. pyogenes infections can be followed by nonsuppurative (without the production of pus) sequelae that develop 1–3 weeks after the acute infection has resolved. Two such sequelae are acute rheumatic fever and acute glomerulonephritis.
Acute rheumatic fever can follow pharyngitis caused by specific rheumatogenic strains of S. pyogenes (strains 1, 3, 5, 6, and 18). Although the exact mechanism responsible for this sequela remains unclear, molecular mimicry between the M protein of rheumatogenic strains of S. pyogenes and heart tissue is thought to initiate the autoimmune attack. The most serious and lethal clinical manifestation of rheumatic fever is damage to and inflammation of the heart (carditis). Acute glomerulonephritis also results from an immune response to streptococcal antigens following pharyngitis and cutaneous infections. Acute glomerulonephritis develops within 6–10 days after pharyngitis, but can take up to 21 days after a cutaneous infection. Similar to acute rheumatic fever, there are strong associations between specific nephritogenic strains of S. pyogenes and acute glomerulonephritis, and evidence suggests a role for antigen mimicry and autoimmunity. However, the primary mechanism of acute glomerulonephritis appears to be the formation of immune complexes between S. pyogenes antigens and antibodies, and their deposition between endothelial cells of the glomeruli of kidney. Inflammatory response against the immune complexes leads to damage and inflammation of the glomeruli (glomerulonephritis).
- What are the symptoms of strep throat?
- What is erythrogenic toxin and what effect does it have?
- What are the causes of rheumatic fever and acute glomerulonephritis?
Acute Otitis Media
An infection of the middle ear is called acute otitis media (AOM), but often it is simply referred to as an earache. The condition is most common between ages 3 months and 3 years. In the United States, AOM is the second-leading cause of visits to pediatricians by children younger than age 5 years, and it is the leading indication for antibiotic prescription. 2
AOM is characterized by the formation and accumulation of pus in the middle ear. Unable to drain, the pus builds up, resulting in moderate to severe bulging of the tympanic membrane and otalgia (ear pain). Inflammation resulting from the infection leads to swelling of the eustachian tubes, and may also lead to fever, nausea, vomiting, and diarrhea, particularly in infants. Infants and toddlers who cannot yet speak may exhibit nonverbal signs suggesting AOM, such as holding, tugging, or rubbing of the ear, as well as uncharacteristic crying or distress in response to the pain.
AOM can be caused by a variety of bacteria. Among neonates, S. pneumoniae is the most common cause of AOM, but Escherichia coli , Enterococcus spp., and group B Streptococcus species can also be involved. In older infants and children younger than 14 years old, the most common bacterial causes are S. pneumoniae , Haemophilus influenzae , or Moraxella catarrhalis . Among S. pneumoniae infections , encapsulated strains are frequent causes of AOM. By contrast, the strains of H. influenzae and M. cattarhalis that are responsible for AOM do not possess a capsule. Rather than direct tissue damage by these pathogens, bacterial components such as lipopolysaccharide (LPS) in gram-negative pathogens induce an inflammatory response that causes swelling, pus, and tissue damage within the middle ear (Figure \(\PageIndex{3}\)).
Any blockage of the eustachian tubes, with or without infection, can cause fluid to become trapped and accumulate in the middle ear. This is referred to as otitis media with effusion (OME). The accumulated fluid offers an excellent reservoir for microbial growth and, consequently, secondary bacterial infections often ensue. This can lead to recurring and chronic earaches, which are especially common in young children. The higher incidence in children can be attributed to many factors. Children have more upper respiratory infections, in general, and their eustachian tubes are also shorter and drain at a shallower angle. Young children also tend to spend more time lying down than adults, which facilitates drainage from the nasopharynx through the eustachian tube and into the middle ear. Bottle feeding while lying down enhances this risk because the sucking action on the bottle causes negative pressure to build up within the eustachian tube, promoting the movement of fluid and bacteria from the nasopharynx.
Diagnosis is typically made based on clinical signs and symptoms, without laboratory testing to determine the specific causative agent. Antibiotics are frequently prescribed for the treatment of AOM. High-dose amoxicillin is the first-line drug, but with increasing resistance concerns, macrolides and cephalosporins may also be used. The pneumococcal conjugate vaccine (PCV13) contains serotypes that are important causes of AOM, and vaccination has been shown to decrease the incidence of AOM. Vaccination against influenza has also been shown to decrease the risk for AOM, likely because viral infections like influenza predispose patients to secondary infections with S. pneumoniae . Although there is a conjugate vaccine available for the invasive serotype B of H. influenzae , this vaccine does not impact the incidence of H. influenzae AOM. Because unencapsulated strains of H. influenzae and M. catarrhalis are involved in AOM, vaccines against bacterial cellular factors other than capsules will need to be developed.
Bacterial Rhinosinusitis
The microbial community of the nasopharynx is extremely diverse and harbors many opportunistic pathogens, so it is perhaps not surprising that infections leading to rhinitis and sinusitis have many possible causes. These conditions often occur as secondary infections after a viral infection, which effectively compromises the immune defenses and allows the opportunistic bacteria to establish themselves. Bacterial sinusitis involves infection and inflammation within the paranasal sinuses. Because bacterial sinusitis rarely occurs without rhinitis, the preferred term is rhinosinusitis. The most common causes of bacterial rhinosinusitis are similar to those for AOM, including S. pneumoniae , H. influenzae , and M. catarrhalis .
- What are the usual causative agents of acute otitis media?
- What factors facilitate acute otitis media with effusion in young children?
- What factor often triggers bacterial rhinosinusitis?
Diphtheria
The causative agent of diphtheria, Corynebacterium diphtheriae , is a club-shaped, gram-positive rod that belongs to the phylum Actinobacteria. Diphtheroids are common members of the normal nasopharyngeal microbiota. However, some strains of C. diphtheriae become pathogenic because of the presence of a temperate bacteriophage-encoded protein—the diphtheria toxin. Diphtheria is typically a respiratory infection of the oropharynx but can also cause impetigo-like lesions on the skin. Although the disease can affect people of all ages, it tends to be most severe in those younger than 5 years or older than 40 years. Like strep throat, diphtheria is commonly transmitted in the droplets and aerosols produced by coughing. After colonizing the throat, the bacterium remains in the oral cavity and begins producing the diphtheria toxin. This protein is an A-B toxin that blocks host-cell protein synthesis by inactivating elongation factor (EF)-2 (see Virulence Factors of Bacterial and Viral Pathogens ). The toxin’s action leads to the death of the host cells and an inflammatory response. An accumulation of grayish exudate consisting of dead host cells, pus, red blood cells, fibrin, and infectious bacteria results in the formation of a pseudomembrane. The pseudomembrane can cover mucous membranes of the nasal cavity, tonsils, pharynx, and larynx (Figure \(\PageIndex{4}\)). This is a classic sign of diphtheria. As the disease progresses, the pseudomembrane can enlarge to obstruct the fauces of the pharynx or trachea and can lead to suffocation and death. Sometimes, intubation, the placement of a breathing tube in the trachea, is required in advanced infections. If the diphtheria toxin spreads throughout the body, it can damage other tissues as well. This can include myocarditis (heart damage) and nerve damage that may impair breathing.
The presumptive diagnosis of diphtheria is primarily based on the clinical symptoms (i.e., the pseudomembrane) and vaccination history, and is typically confirmed by identifying bacterial cultures obtained from throat swabs. The diphtheria toxin itself can be directly detected in vitro using polymerase chain reaction (PCR)-based, direct detection systems for the diphtheria tox gene, and immunological techniques like radial immunodiffusion or Elek’s immunodiffusion test.
Broad-spectrum antibiotics like penicillin and erythromycin tend to effectively control C. diphtheriae infections. Regrettably, they have no effect against preformed toxins. If toxin production has already occurred in the patient, antitoxins (preformed antibodies against the toxin) are administered. Although this is effective in neutralizing the toxin, the antitoxins may lead to serum sickness because they are produced in horses (see Hypersensitivities ).
Widespread vaccination efforts have reduced the occurrence of diphtheria worldwide. There are currently four combination toxoid vaccines available that provide protection against diphtheria and other diseases: DTaP, Tdap, DT, and Td. In all cases, the letters “d,” “t,” and “p” stand for diphtheria, tetanus, and pertussis, respectively; the “a” stands for acellular. If capitalized, the letters indicate a full-strength dose; lowercase letters indicate reduced dosages. According to current recommendations, children should receive five doses of the DTaP vaccine in their youth and a Td booster every 10 years. Children with adverse reactions to the pertussis vaccine may be given the DT vaccine in place of the DTaP.
- What effect does diphtheria toxin have?
- What is the pseudomembrane composed of?
Bacterial Pneumonia
Pneumonia is a general term for infections of the lungs that lead to inflammation and accumulation of fluids and white blood cells in the alveoli. Pneumonia can be caused by bacteria, viruses, fungi, and other organisms, although the vast majority of pneumonias are bacterial in origin. Bacterial pneumonia is a prevalent, potentially serious infection; it caused more 50,000 deaths in the United States in 2014. 3 As the alveoli fill with fluids and white blood cells (consolidation), air exchange becomes impaired and patients experience respiratory distress (Figure \(\PageIndex{5}\)). In addition, pneumonia can lead to pleurisy, an infection of the pleural membrane surrounding the lungs, which can make breathing very painful. Although many different bacteria can cause pneumonia under the right circumstances, three bacterial species cause most clinical cases: Streptococcus pneumoniae , H . influenzae , and Mycoplasma pneumoniae . In addition to these, we will also examine some of the less common causes of pneumonia.
Pneumococcal Pneumonia
The most common cause of community-acquired bacterial pneumonia is Streptococcus pneumoniae . This gram-positive, alpha hemolytic streptococcus is commonly found as part of the normal microbiota of the human respiratory tract. The cells tend to be somewhat lancet-shaped and typically appear as pairs (Figure \(\PageIndex{6}\)). The pneumococci initially colonize the bronchioles of the lungs. Eventually, the infection spreads to the alveoli, where the microbe’s polysaccharide capsule interferes with phagocytic clearance. Other virulence factors include autolysins like Lyt A, which degrade the microbial cell wall, resulting in cell lysis and the release of cytoplasmic virulence factors. One of these factors, pneumolysin O, is important in disease progression; this pore-forming protein damages host cells, promotes bacterial adherence, and enhances pro-inflammatory cytokine production. The resulting inflammatory response causes the alveoli to fill with exudate rich in neutrophils and red blood cells.
Pneumococci can be presumptively identified by their distinctive gram-positive, lancet-shaped cell morphology and diplococcal arrangement. In blood agar cultures, the organism demonstrates alpha hemolytic colonies that are autolytic after 24 to 48 hours. In addition, S. pneumoniae is extremely sensitive to optochin and colonies are rapidly destroyed by the addition of 10% solution of sodium deoxycholate. All clinical pneumococcal isolates are serotyped using the quellung reaction with typing antisera produced by the CDC. Positive quellung reactions are considered definitive identification of pneumococci.
Antibiotics remain the mainstay treatment for pneumococci. β-Lactams like penicillin are the first-line drugs, but resistance to β-lactams is a growing problem. When β-lactam resistance is a concern, macrolides and fluoroquinolones may be prescribed. However, S. pneumoniae resistance to macrolides and fluoroquinolones is increasing as well, limiting the therapeutic options for some infections. There are currently two pneumococcal vaccines available: pneumococcal conjugate vaccine (PCV13) and pneumococcal polysaccharide vaccine (PPSV23). These are generally given to the most vulnerable populations of individuals: children younger than 2 years and adults older than 65 years.
Haemophilus Pneumonia
Encapsulated strains of Haemophilus influenzae are known for causing meningitis, but nonencapsulated strains are important causes of pneumonia. This small, gram-negative coccobacillus is found in the pharynx of the majority of healthy children; however, Haemophilus pneumonia is primarily seen in the elderly. Like other pathogens that cause pneumonia, H. influenzae is spread by droplets and aerosols produced by coughing. A fastidious organism, H. influenzae will only grow on media with available factor X (hemin) and factor V (NAD), like chocolate agar (Figure \(\PageIndex{7}\)). Serotyping must be performed to confirm identity of H. influenzae isolates.
Infections of the alveoli by H. influenzae result in inflammation and accumulation of fluids. Increasing resistance to β-lactams, macrolides, and tetracyclines presents challenges for the treatment of Haemophilus pneumonia. Resistance to the fluoroquinolones is rare among isolates of H. influenzae but has been observed. As discussed for AOM, a vaccine directed against nonencapsulated H. influenzae, if developed, would provide protection against pneumonia caused by this pathogen.
Tracy is a 6-year old who developed a serious cough that would not seem to go away. After 2 weeks, her parents became concerned and took her to the pediatrician, who suspected a case of bacterial pneumonia. Tests confirmed that the cause was Haemophilus influenzae . Fortunately, Tracy responded well to antibiotic treatment and eventually made a full recovery.
Because there had been several other cases of bacterial pneumonia at Tracy’s elementary school, local health officials urged parents to have their children screened. Of the children who were screened, it was discovered that greater than 50% carried H. influenzae in their nasal cavities, yet all but two of them were asymptomatic.
Why is it that some individuals become seriously ill from bacterial infections that seem to have little or no effect on others? The pathogenicity of an organism—its ability to cause host damage—is not solely a property of the microorganism. Rather, it is the product of a complex relationship between the microbe’s virulence factors and the immune defenses of the individual. Preexisting conditions and environmental factors such as exposure to secondhand smoke can make some individuals more susceptible to infection by producing conditions favorable to microbial growth or compromising the immune system. In addition, individuals may have genetically determined immune factors that protect them—or not—from particular strains of pathogens. The interactions between these host factors and the pathogenicity factors produced by the microorganism ultimately determine the outcome of the infection. A clearer understanding of these interactions may allow for better identification of at-risk individuals and prophylactic interventions in the future.
Mycoplasma Pneumonia (Walking Pneumonia)
Primary atypical pneumonia is caused by Mycoplasma pneumoniae . This bacterium is not part of the respiratory tract’s normal microbiota and can cause epidemic disease outbreaks. Also known as walking pneumonia, mycoplasma pneumonia infections are common in crowded environments like college campuses and military bases. It is spread by aerosols formed when coughing or sneezing. The disease is often mild, with a low fever and persistent cough. These bacteria, which do not have cell walls, use a specialized attachment organelle to bind to ciliated cells. In the process, epithelial cells are damaged and the proper function of the cilia is hindered (Figure \(\PageIndex{8}\)).
Mycoplasma grow very slowly when cultured. Therefore, penicillin and thallium acetate are added to agar to prevent the overgrowth by faster-growing potential contaminants. Since M. pneumoniae does not have a cell wall, it is resistant to these substances. Without a cell wall, the microbial cells appear pleomorphic. M. pneumoniae infections tend to be self-limiting but may also respond well to macrolide antibiotic therapy. β-lactams, which target cell wall synthesis, are not indicated for treatment of infections with this pathogen.
Chlamydial Pneumonias and Psittacosis
Chlamydial pneumonia can be caused by three different species of bacteria: Chlamydophila pneumoniae (formerly known as Chlamydia pneumoniae ), Chlamydophila psittaci (formerly known as Chlamydia psittaci ), and Chlamydia trachomatis . All three are obligate intracellular pathogens and cause mild to severe pneumonia and bronchitis. Of the three, Chlamydophila pneumoniae is the most common and is transmitted via respiratory droplets or aerosols. C. psittaci causes psittacosis, a zoonotic disease that primarily affects domesticated birds such as parakeets, turkeys, and ducks, but can be transmitted from birds to humans. Psittacosis is a relatively rare infection and is typically found in people who work with birds. Chlamydia trachomatis, the causative agent of the sexually transmitted disease chlamydia, can cause pneumonia in infants when the infection is passed from mother to baby during birth.
Diagnosis of chlamydia by culturing tends to be difficult and slow. Because they are intracellular pathogens, they require multiple passages through tissue culture. Recently, a variety of PCR- and serologically based tests have been developed to enable easier identification of these pathogens. Tetracycline and macrolide antibiotics are typically prescribed for treatment.
Health Care-Associated Pneumonia
A variety of opportunistic bacteria that do not typically cause respiratory disease in healthy individuals are common causes of health care-associated pneumonia. These include Klebsiella pneumoniae , Staphylococcus aureus , and proteobacteria such as species of Escherichia , Proteus , and Serratia . Patients at risk include the elderly, those who have other preexisting lung conditions, and those who are immunocompromised. In addition, patients receiving supportive therapies such as intubation, antibiotics, and immunomodulatory drugs may also be at risk because these interventions disrupt the mucociliary escalator and other pulmonary defenses. Invasive medical devices such as catheters, medical implants, and ventilators can also introduce opportunistic pneumonia-causing pathogens into the body. 4
Pneumonia caused by K. pneumoniae is characterized by lung necrosis and “currant jelly sputum,” so named because it consists of clumps of blood, mucus, and debris from the thick polysaccharide capsule produced by the bacterium. K. pneumoniae is often multidrug resistant. Aminoglycoside and cephalosporin are often prescribed but are not always effective. Klebsiella pneumonia is frequently fatal even when treated.
Pseudomonas Pneumonia
Pseudomonas aeruginosa is another opportunistic pathogen that can cause serious cases of bacterial pneumonia in patients with cystic fibrosis (CF) and hospitalized patients assisted with artificial ventilators. This bacterium is extremely antibiotic resistant and can produce a variety of exotoxins. Ventilator-associated pneumonia with P. aeruginosa is caused by contaminated equipment that causes the pathogen to be aspirated into the lungs. In patients with CF, a genetic defect in the cystic fibrosis transmembrane receptor (CFTR) leads to the accumulation of excess dried mucus in the lungs. This decreases the effectiveness of the defensins and inhibits the mucociliary escalator. P. aeruginosa is known to infect more than half of all patients with CF. It adapts to the conditions in the patient’s lungs and begins to produce alginate, a viscous exopolysaccharide that inhibits the mucociliary escalator. Lung damage from the chronic inflammatory response that ensues is the leading cause of mortality in patients with CF. 5
- What three pathogens are responsible for the most prevalent types of bacterial pneumonia?
- Which cause of pneumonia is most likely to affect young people?
- In what contexts does Pseudomonas aeruginosa cause pneumonia?
John’s chest radiograph revealed an extensive consolidation in the right lung, and his sputum cultures revealed the presence of a gram-negative rod. His physician prescribed a course of the antibiotic clarithromycin. He also ordered the rapid influenza diagnostic tests (RIDTs) for type A and B influenza to rule out a possible underlying viral infection. Despite antibiotic therapy, John’s condition continued to deteriorate, so he was admitted to the hospital.
What are some possible causes of pneumonia that would not have responded to the prescribed antibiotic?
Tuberculosis
Tuberculosis (TB) is one of the deadliest infectious diseases in human history. Although tuberculosis infection rates in the United States are extremely low, the CDC estimates that about one-third of the world’s population is infected with Mycobacterium tuberculosis , the causal organism of TB, with 9.6 million new TB cases and 1.5 million deaths worldwide in 2014. 6
M. tuberculosis is an acid-fast, high G + C, gram-positive, nonspore-forming rod. Its cell wall is rich in waxy mycolic acids, which make the cells impervious to polar molecules. It also causes these organisms to grow slowly. M. tuberculosis causes a chronic granulomatous disease that can infect any area of the body, although it is typically associated with the lungs. M. tuberculosis is spread by inhalation of respiratory droplets or aerosols from an infected person. The infectious dose of M. tuberculosis is only 10 cells. 7
After inhalation, the bacteria enter the alveoli (Figure \(\PageIndex{9}\)). The cells are phagocytized by macrophages but can survive and multiply within these phagocytes because of the protection by the waxy mycolic acid in their cell walls. If not eliminated by macrophages, the infection can progress, causing an inflammatory response and an accumulation of neutrophils and macrophages in the area. Several weeks or months may pass before an immunological response is mounted by T cells and B cells. Eventually, the lesions in the alveoli become walled off, forming small round lesions called tubercles. Bacteria continue to be released into the center of the tubercles and the chronic immune response results in tissue damage and induction of apoptosis (programmed host-cell death) in a process called liquefaction. This creates a caseous center, or air pocket, where the aerobic M. tuberculosis can grow and multiply. Tubercles may eventually rupture and bacterial cells can invade pulmonary capillaries; from there, bacteria can spread through the bloodstream to other organs, a condition known as miliary tuberculosis. The rupture of tubercles also facilitates transmission of the bacteria to other individuals via droplet aerosols that exit the body in coughs. Because these droplets can be very small and stay aloft for a long time, special precautions are necessary when caring for patients with TB, such as the use of face masks and negative-pressure ventilation and filtering systems.
Eventually, most lesions heal to form calcified Ghon complexes.  But even after the disease has apparently ended, viable bacteria remain sequestered in these locations. Release of these organisms at a later time can produce reactivation tuberculosis (or secondary TB). This is mainly observed in people with alcoholism, the elderly, or in otherwise immunocompromised individuals (Figure \(\PageIndex{9}\)).
Because TB is a chronic disease, chemotherapeutic treatments often continue for months or years. Multidrug resistant (MDR-TB) and extensively drug-resistant (XDR-TB) strains of M. tuberculosis are a growing clinical concern. These strains can arise due to misuse or mismanagement of antibiotic therapies. Therefore, it is imperative that proper multidrug protocols are used to treat these infections. Common antibiotics included in these mixtures are isoniazid, rifampin, ethambutol, and pyrazinamide.
A TB vaccine is available that is based on the so-called bacillus Calmette-Guérin (BCG) strain of M. bovis commonly found in cattle. In the United States, the BCG vaccine is only given to health-care workers and members of the military who are at risk of exposure to active cases of TB. It is used more broadly worldwide. Many individuals born in other countries have been vaccinated with BCG strain. BCG is used in many countries with a high prevalence of TB, to prevent childhood tuberculous meningitis and miliary disease.
The Mantoux tuberculin skin test (Figure \(\PageIndex{10}\)) is regularly used in the United States to screen for potential TB exposure (see Hypersensitivities ). However, prior vaccinations with the BCG vaccine can cause false-positive results. Chest radiographs to detect Ghon complex formation are required, therefore, to confirm exposure.
- What characteristic of Mycobacterium tuberculosis allows it to evade the immune response?
- What happens to cause miliary tuberculosis?
- Explain the limitations of the Mantoux tuberculin skin test.
Pertussis (Whooping Cough)
The causative agent of pertussis, commonly called whooping cough, is Bordetella pertussis , a gram-negative coccobacillus. The disease is characterized by mucus accumulation in the lungs that leads to a long period of severe coughing. Sometimes, following a bout of coughing, a sound resembling a “whoop” is produced as air is inhaled through the inflamed and restricted airway—hence the name whooping cough. Although adults can be infected, the symptoms of this disease are most pronounced in infants and children. Pertussis is highly communicable through droplet transmission, so the uncontrollable coughing produced is an efficient means of transmitting the disease in a susceptible population.
Following inhalation, B. pertussis specifically attaches to epithelial cells using an adhesin, filamentous hemagglutinin. The bacteria then grow at the site of infection and cause disease symptoms through the production of exotoxins. One of the main virulence factors of this organism is an A-B exotoxin called the pertussis toxin (PT). When PT enters the host cells, it increases the cyclic adenosine monophosphate (cAMP) levels and disrupts cellular signaling. PT is known to enhance inflammatory responses involving histamine and serotonin. In addition to PT, B. pertussis produces a tracheal cytotoxin that damages ciliated epithelial cells and results in accumulation of mucus in the lungs. The mucus can support the colonization and growth of other microbes and, as a consequence, secondary infections are common. Together, the effects of these factors produce the cough that characterizes this infection.
A pertussis infection can be divided into three distinct stages. The initial infection, termed the catarrhal stage, is relatively mild and unremarkable. The signs and symptoms may include nasal congestion, a runny nose, sneezing, and a low-grade fever. This, however, is the stage in which B. pertussis is most infectious. In the paroxysmal stage, mucus accumulation leads to uncontrollable coughing spasms that can last for several minutes and frequently induce vomiting. The paroxysmal stage can last for several weeks. A long convalescence stage follows the paroxysmal stage, during which time patients experience a chronic cough that can last for up to several months. In fact, the disease is sometimes called the 100-day cough.
In infants, coughing can be forceful enough to cause fractures to the ribs, and prolonged infections can lead to death. The CDC reported 20 pertussis-related deaths in 2012, 9 but that number had declined to five by 2015. 10
During the first 2 weeks of infection, laboratory diagnosis is best performed by culturing the organism directly from a nasopharyngeal (NP) specimen collected from the posterior nasopharynx. The NP specimen is streaked onto Bordet-Gengou medium. The specimens must be transported to the laboratory as quickly as possible, even if transport media are used. Transport times of longer than 24 hours reduce the viability of B. pertussis significantly.
Within the first month of infection, B. pertussis can be diagnosed using PCR techniques. During the later stages of infection, pertussis-specific antibodies can be immunologically detected using an enzyme-linked immunosorbent assay (ELISA).
Pertussis is generally a self-limiting disease. Antibiotic therapy with erythromycin or tetracycline is only effective at the very earliest stages of disease. Antibiotics given later in the infection, and prophylactically to uninfected individuals, reduce the rate of transmission. Active vaccination is a better approach to control this disease. The DPT vaccine was once in common use in the United States. In that vaccine, the P component consisted of killed whole-cell B. pertussis preparations. Because of some adverse effects, that preparation has now been superseded by the DTaP and Tdap vaccines. In both of these new vaccines, the “aP” component is a pertussis toxoid.
Widespread vaccination has greatly reduced the number of reported cases and prevented large epidemics of pertussis. Recently, however, pertussis has begun to reemerge as a childhood disease in some states because of declining vaccination rates and an increasing population of susceptible children.
- What accounts for the mucus production in a pertussis infection?
- What are the signs and symptoms associated with the three stages of pertussis?
- Why is pertussis becoming more common in the United States?
Legionnaires Disease
An atypical pneumonia called Legionnaires disease (also known as legionellosis) is caused by an aerobic gram-negative bacillus, Legionella pneumophila . This bacterium infects free-living amoebae that inhabit moist environments, and infections typically occur from human-made reservoirs such as air-conditioning cooling towers, humidifiers, misting systems, and fountains. Aerosols from these reservoirs can lead to infections of susceptible individuals, especially those suffering from chronic heart or lung disease or other conditions that weaken the immune system.
When L. pneumophila bacteria enter the alveoli, they are phagocytized by resident macrophages. However, L. pneumophila uses a secretion system to insert proteins in the endosomal membrane of the macrophage; these proteins prevent lysosomal fusion, allowing L. pneumophila to continue to proliferate within the phagosome. The resulting respiratory disease can range from mild to severe pneumonia, depending on the status of the host’s immune defenses. Although this disease primarily affects the lungs, it can also cause fever, nausea, vomiting, confusion, and other neurological effects.
Diagnosis of Legionnaires disease is somewhat complicated. L. pneumophila is a fastidious bacterium and is difficult to culture. In addition, since the bacterial cells are not efficiently stained with the Gram stain, other staining techniques, such as the Warthin-Starry silver-precipitate procedure, must be used to visualize this pathogen. A rapid diagnostic test has been developed that detects the presence of Legionella antigen in a patient’s urine; results take less than 1 hour, and the test has high selectivity and specificity (greater than 90%). Unfortunately, the test only works for one serotype of L. pneumophila (type 1, the serotype responsible for most infections). Consequently, isolation and identification of L. pneumophila from sputum remains the defining test for diagnosis.
Once diagnosed, Legionnaire disease can be effectively treated with fluoroquinolone and macrolide antibiotics. However, the disease is sometimes fatal; about 10% of patients die of complications. 11 There is currently no vaccine available.
- Why is Legionnaires disease associated with air-conditioning systems?
- How does Legionella pneumophila circumvent the immune system?
Q Fever
The zoonotic disease Q fever is caused by a rickettsia, Coxiella burnetii . The primary reservoirs for this bacterium are domesticated livestock such as cattle, sheep, and goats. The bacterium may be transmitted by ticks or through exposure to the urine, feces, milk, or amniotic fluid of an infected animal. In humans, the primary route of infection is through inhalation of contaminated farmyard aerosols. It is, therefore, largely an occupational disease of farmers. Humans are acutely sensitive to C. burnetii —the infective dose is estimated to be just a few cells. 12 In addition, the organism is hardy and can survive in a dry environment for an extended time. Symptoms associated with acute Q fever include high fever, headache, coughing, pneumonia, and general malaise. In a small number of patients (less than 5% 13 ), the condition may become chronic, often leading to endocarditis, which may be fatal.
Diagnosing rickettsial infection by cultivation in the laboratory is both difficult and hazardous because of the easy aerosolization of the bacteria, so PCR and ELISA are commonly used. Doxycycline is the first-line drug to treat acute Q fever. In chronic Q fever, doxycycline is often paired with hydroxychloroquine.
Numerous pathogens can cause infections of the respiratory tract. Many of these infections produce similar signs and symptoms, but appropriate treatment depends on accurate diagnosis through laboratory testing. The tables in Figure \(\PageIndex{11}\) and Figure \(\PageIndex{12}\) summarize the most important bacterial respiratory infections, with the latter focusing specifically on forms of bacterial pneumonia.
Key Concepts and Summary
- A wide variety of bacteria can cause respiratory diseases; most are treatable with antibiotics or preventable with vaccines.
- Streptococcus pyogenes causes strep throat , an infection of the pharynx that also causes high fever and can lead to scarlet fever , acute rheumatic fever , and acute glomerulonephritis .
- Acute otitis media is an infection of the middle ear that may be caused by several bacteria, including Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis . The infection can block the eustachian tubes, leading to otitis media with effusion .
- Diphtheria , caused by Corynebacterium diphtheriae , is now a rare disease because of widespread vaccination. The bacteria produce exotoxins that kill cells in the pharynx, leading to the formation of a pseudomembrane ; and damage other parts of the body.
- Bacterial pneumonia results from infections that cause inflammation and fluid accumulation in the alveoli. It is most commonly caused by S. pneumoniae or H. influenzae . The former is commonly multidrug resistant.
- Mycoplasma pneumonia results from infection by Mycoplasma pneumoniae ; it can spread quickly, but the disease is mild and self-limiting.
- Chlamydial pneumonia can be caused by three pathogens that are obligate intracellular parasites. Chlamydophila pneumoniae is typically transmitted from an infected person, whereas C. psittaci is typically transmitted from an infected bird. Chlamydia trachomatis , may cause pneumonia in infants.
- Several other bacteria can cause pneumonia in immunocompromised individuals and those with cystic fibrosis.
- Tuberculosis is caused by Mycobacterium tuberculosis . Infection leads to the production of protective tubercles in the alveoli and calcified Ghon complexes that can harbor the bacteria for a long time. Antibiotic-resistant forms are common and treatment is typically long term.
- Pertussis is caused by Bordetella pertussis . Mucus accumulation in the lungs leads to prolonged severe coughing episodes (whooping cough) that facilitate transmission. Despite an available vaccine, outbreaks are still common.
- Legionnaires disease is caused by infection from environmental reservoirs of the Legionella pneumophila bacterium. The bacterium is endocytic within macrophages and infection can lead to pneumonia, particularly among immunocompromised individuals.
- Q fever is caused by Coxiella burnetii , whose primary hosts are domesticated mammals (zoonotic disease). It causes pneumonia primarily in farm workers and can lead to serious complications, such as endocarditis.
Footnotes
- 1 WL Lean et al. “Rapid Diagnostic Tests for Group A Streptococcal Pharyngitis: A Meta-Analysis.” Pediatrics 134, no. 4 (2014):771–781.
- 2 G. Worrall. “Acute Otitis Media.” Canadian Family Physician 53 no. 12 (2007):2147–2148.
- 3 KD Kochanek et al. “Deaths: Final Data for 2014.” National Vital Statistics Reports 65 no 4 (2016).
- 4 SM Koenig et al. “Ventilator-Associated Pneumonia: Diagnosis, Treatment, and Prevention.” Clinical Microbiology Reviews 19 no. 4 (2006):637–657.
- 5 R. Sordé et al. “Management of Refractory Pseudomonas aeruginosa Infection in Cystic Fibrosis.” Infection and Drug Resistance 4 (2011):31–41.
- 6 Centers for Disease Control and Prevention. “Tuberculosis (TB). Data and Statistics.” http://www.cdc.gov/tb/statistics/default.htm
- 7 D. Saini et al. “Ultra-Low Dose of Mycobacterium tuberculosis Aerosol Creates Partial Infection in Mice.” Tuberculosis 92 no. 2 (2012):160–165.
- 8 G. Kaplan et al. “ Mycobacterium tuberculosis Growth at the Cavity Surface: A Microenvironment with Failed Immunity.” Infection and Immunity 71 no.12 (2003):7099–7108.
- 9 Centers for Disease Control and Prevention. “2012 Final Pertussis Surveillance Report.” 2015. http://www.cdc.gov/pertussis/downloa...eport-2012.pdf . Accessed July 6, 2016.
- 10 Centers for Disease Control and Prevention. “2015 Provisional Pertussis Surveillance Report.” 2016. http://www.cdc.gov/pertussis/downloa...rovisional.pdf . Accessed July 6, 2016.
- 11 Centers for Disease Control and Prevention. “ Legionella (Legionnaires’ Disease and Pontiac Fever: Diagnosis, Treatment, and Complications).” http://www.cdc.gov/legionella/about/diagnosis.html . Accessed Sept 14, 2016.
- 12 WD Tigertt et al. “Airborne Q Fever.” Bacteriological Reviews 25 no. 3 (1961):285–293.
- 13 Centers for Disease Control and Prevention. “Q fever. Symptoms, Diagnosis, and Treatment.” 2013. http://www.cdc.gov/qfever/symptoms/index.html . Accessed July 6, 2016.


7.2: Symphony Orchestras
Introduction
An orchestra is a large instrumental ensemble that contains sections of string (violin, viola, cello, and double bass), brass, woodwind, and percussion instruments. Other instruments such as the piano and celesta may sometimes be grouped into a fifth section such as a keyboard section or may stand alone, as may the concert harp and electric and electronic instruments. The orchestra grew by accretion throughout the eighteenth and nineteenth centuries, but changed very little in composition during the course of the twentieth century.
A smaller-sized orchestra for this time period (of about fifty musicians or fewer) is called a chamber orchestra. A full-size orchestra (about one hundred musicians) may sometimes be called a symphony orchestra or philharmonic orchestra; these modifiers do not necessarily indicate any strict difference in either the instrumental constitution or role of the orchestra, but can be useful to distinguish different ensembles based in the same city (for instance, the London Symphony Orchestra and the London Philharmonic Orchestra). A symphony orchestra will usually have over eighty musicians on its roster, in some cases over a hundred, but the actual number of musicians employed in a particular performance may vary according to the work being played and the size of the venue. A leading chamber orchestra might employ as many as fifty musicians; some are much smaller than that. The term concert orchestra may sometimes be used (e.g., BBC Concert Orchestra; RTÉ Concert Orchestra)—no distinction is made on size of orchestra by use of this term, although their use is generally distinguished as for live concert. As such they are commonly chamber orchestras. There are several types of amateur orchestras, including school orchestras, youth orchestras and community orchestras.
Orchestras are usually led by a conductor who directs the performance by way of visible gestures. The conductor unifies the orchestra, sets the tempo and shapes the sound of the ensemble.
Instrumentation
The typical symphony orchestra consists of four groups of related musical instruments called the woodwinds, brass, percussion, and strings (violin, viola, cello, and double bass). Other instruments such as the piano and celesta may sometimes be grouped into a fifth section such as a keyboard section or may stand alone, as may the concert harp and electric and electronic instruments. The orchestra, depending on the size, contains almost all of the standard instruments in each group. In the history of the orchestra, its instrumentation has been expanded over time, often agreed to have been standardized by the classical period and Ludwig van Beethoven’s influence on the classical model. In the twentieth century, new repertory (musical pieces) demands expanded the instrumentation of the orchestra, resulting in a flexible use of the classical model instruments in various combinations.
Organization
Among the instrument groups and within each group of instruments, there is a generally accepted hierarchy. Every instrumental group (or section) has a principal who is generally responsible for leading the group and playing orchestral solos. The violins are divided into two groups, first violin and second violin, with the second violins playing with lower registers than the first violins.
The principal first violin is called the concertmaster (or “leader” in the UK) and is not only considered the leader of the string section, but the second-in-command of the entire orchestra, behind only the conductor. The concertmaster leads the pre-concert tuning and handles musical aspects of orchestra management, such as determining the bowings for the violins or for all of the string section. The concertmaster usually sits to the conductor’s left, closest to the audience. In some U.S. and British orchestras, the concertmaster comes on stage after the rest of the orchestra is seated, takes a bow, and receives applause before the conductor (and the soloists, if there are any) appear on stage.
The principal trombone is considered the leader of the low brass section, while the principal trumpet is generally considered the leader of the entire brass section. While the oboe often provides the tuning note for the orchestra (due to three-hundred-year-old convention), no principal is the leader of the woodwind section though in woodwind ensembles, often the flute is leader. Instead, each principal confers with the others as equals in the case of musical differences of opinion. The horn, while technically a brass instrument, often acts in the role of both woodwind and brass. Most sections also have an assistant principal (or co-principal or associate principal), or in the case of the first violins, an assistant concertmaster, who often plays a tutti (all together) part in addition to replacing the principal in his or her absence.
A section string player plays in unison with the rest of the section, except in the case of divided ( divisi ) parts, where upper and lower parts in the music are often assigned to “outside” (nearer the audience) and “inside” seated players. Where a solo part is called for in a string section, the section leader invariably plays that part. The section leader (or principal) of a string section is also responsible for determining the bowings, often based on the bowings set out by the concertmaster. In some cases, the principal of a string section may use a slightly different bowing than the Concertmaster, to accommodate the requirements of playing their instrument (e.g., the double bass section). Principals of a string section will also lead entrances for their section, typically by lifting the bow before the entrance, to ensure the section plays together. Tutti wind and brass players generally play a unique but non-solo part. Section percussionists play parts assigned to them by the principal percussionist.
The Conductor
Conducting is the art of directing a musical performance, such as a concert, by way of visible gestures with the hands, arms, face and head. The primary duties of the conductor are to unify performers, set the tempo, execute clear preparations and beats (meter), and to listen critically and shape the sound of the ensemble.
In the following video, Leonard Bernstein, one of the most famous modern conductors, is shown conducting the London Symphony Orchestra as they play the Candide Overture. Note his body language and facial expressions as he leads the orchestra.
The conductor typically stands on a raised podium and he or she may or may not use a wooden baton. Most conductors do not play an instrument when conducting, but in some cases, a conductor may lead an ensemble while playing a keyboard instrument or the violin, particularly with Baroque music. Communication is typically non-verbal during a performance (this is typically the case in art music, but in jazz big bands or large pop ensembles, there may be occasional spoken instructions.) However in rehearsals, frequent interruptions allow the conductor to give verbal directions as to how the music should be played or sung.
Recent Trends in the United States
In the United States, the late twentieth century saw a crisis of funding and support for orchestras. The size and cost of a symphony orchestra, compared to the size of the base of supporters, became an issue that struck at the core of the institution. Few orchestras could fill auditoriums, and the time-honored season-subscription system became increasingly anachronistic, as more and more listeners would buy tickets on an ad hoc basis for individual events. Orchestral endowments and—more centrally to the daily operation of American orchestras—orchestral donors have seen investment portfolios shrink or produce lower yields, reducing the ability of donors to contribute; further, there has been a trend toward donors finding other social causes more compelling. Also, while government funding is less central to American than European orchestras, cuts in such funding are still significant for American ensembles. Finally, the drastic falling-off of revenues from recording, tied to no small extent to changes in the recording industry itself, began a period of change that has yet to reach its conclusion.
U.S. orchestras that have gone into Chapter 11 bankruptcy include the Philadelphia Orchestra (in April 2011), and the Louisville Orchestra, in December 2010; orchestras that have gone into Chapter 7 bankruptcy and have ceased operations include the Northwest Chamber Orchestra in 2006, the Honolulu Orchestra in March 2011, the New Mexico Symphony Orchestra in April 2011, and the Syracuse Symphony in June 2011. The Festival of Orchestras in Orlando, Florida ceased operations at the end of March, 2011.
Contributors and Attributions
- Orchestra. Provided by : Wikipedia. Located at : https://en.Wikipedia.org/wiki/Orchestra . License : CC BY-SA: Attribution-ShareAlike
- 4.IX Orchestra Sinfonica Nazionale della Rai. Authored by : MITO SettembreMusica. Located at : https://www.flickr.com/photos/mitosettembremusica/2839965900/ . License : CC BY: Attribution
- Candide Overture: Leonard Bernstein conducting. Authored by : nickbigd. Located at : https://youtu.be/422-yb8TXj8 . License : All Rights Reserved . License Terms : Standard YouTube LIcense


5.1: Energy, Matter, and Enzymes
Learning Objectives
- Define and describe metabolism
- Compare and contrast autotrophs and heterotrophs
- Describe the importance of oxidation-reduction reactions in metabolism
- Describe why ATP, FAD, NAD + , and NADP + are important in a cell
- Differentiate between substrate-level and oxidative phosphorylation
- Identify the structure and structural components of an enzyme and the roles of substrates and products in a reaction
The term used to describe all of the chemical reactions inside a cell is metabolism (Figure \(\PageIndex{1}\)). Cellular processes such as the building or breaking down of complex molecules occur through series of stepwise, interconnected chemical reactions called metabolic pathways. Reactions that are spontaneous and release energy are exergonic reactions, whereas endergonic reactions require energy to proceed. The term anabolism refers to those endergonic metabolic pathways involved in biosynthesis, converting simple molecular building blocks into more complex molecules, and fueled by the use of cellular energy, usually in the form of ATP (energy) and/or NAD(P)H (electrons). Conversely, the term catabolism refers to exergonic pathways that break down complex molecules into simpler ones. Molecular energy stored in the bonds of complex molecules is released in catabolic pathways and harvested in such a way that it can be used to produce high-energy molecules (usually in ATP (energy) and/or NADH (electrons)), which are used to drive anabolic pathways. Thus, in terms of energy and molecules, cells are continually balancing catabolism with anabolism.
Oxidation and Reduction in Metabolism
The transfer of electrons between molecules is important because most of the energy stored in atoms and used to fuel cell functions is in the form of high-energy electrons. The transfer of energy in the form of electrons allows the cell to transfer and use energy incrementally; that is, in small packages rather than a single, destructive burst. Reactions that remove electrons from donor molecules, leaving them oxidized, are oxidation reaction s ; those that add electrons to acceptor molecules, leaving them reduced, are reduction reaction s . Because electrons can move from one molecule to another, oxidation and reduction occur in tandem. These pairs of reactions are called oxidation-reduction reactions, or redox reaction s .
Electron Carriers: NAD+, NADP+, and FAD
The energy released from the breakdown of the chemical bonds within nutrients can be stored either through the reduction of electron carriers or in the bonds of adenosine triphosphate (ATP). In living systems, a small class of compounds functions as mobile electron carrier s , molecules that bind to and shuttle high-energy electrons between compounds in pathways. The principal electron carriers we will consider originate from the B vitamin group and are derivatives of nucleotides; they are nicotinamide adenine dinucleotide, nicotine adenine dinucleotide phosphate, and flavin adenine dinucleotide. These compounds can be easily reduced or oxidized. Nicotinamide adenine dinucleotide (NAD + /NADH) is the most common mobile electron carrier used in catabolism. NAD + is the oxidized form of the molecule; NADH is the reduced form of the molecule. Nicotine adenine dinucleotide phosphate (NADP + ), the oxidized form of an NAD + variant that contains an extra phosphate group, is another important electron carrier; it forms NADPH when reduced. The oxidized form of flavin adenine dinucleotide is FAD, and its reduced form is FADH 2 . Both NAD + /NADH and FAD/FADH 2 are extensively used in energy extraction from sugars during catabolism in chemoheterotrophs, whereas NADP + /NADPH plays an important role in anabolic reactions and photosynthesis. Collectively, FADH 2 , NADH, and NADPH are often referred to as having reducing power due to their ability to donate electrons to various chemical reactions.
Energy Carrier: ATP
A living cell must be able to handle the energy released during catabolism in a way that enables the cell to store energy safely and release it for use only as needed. Living cells accomplish this by using the compound adenosine triphosphate (ATP). ATP is often called the “energy currency” of the cell, and, like currency, this versatile compound can be used to fill any energy need of the cell. At the heart of ATP is a molecule of adenosine monophosphate (AMP), which is composed of an adenine molecule bonded to a ribose molecule and a single phosphate group. Ribose is a five-carbon sugar found in RNA, and AMP is one of the nucleotides in RNA. The addition of a second phosphate group to this core molecule results in the formation of adenosine diphosphate (ADP); the addition of a third phosphate group forms ATP (Figure \(\PageIndex{2}\)). Adding a phosphate group to a molecule, a process called phosphorylation, requires energy. Phosphate groups are negatively charged and thus repel one another when they are arranged in series, as they are in ADP and ATP. This repulsion makes the ADP and ATP molecules inherently unstable. Thus, the bonds between phosphate groups (one in ADP and two in ATP) are called high-energy phosphate bond s . When these high-energy bonds are broken to release one phosphate (called inorganic phosphate [P i ]) or two connected phosphate groups (called pyrophosphate [PP i ]) from ATP through a process called dephosphorylation, energy is released to drive endergonic reactions (Figure \(\PageIndex{3}\)).
There are two general mechanisms by which ATP is formed in cells: substrate-level phosphorylation and oxidative phosphorylation (Figure \(\PageIndex{4}\)). Remember that a substrate is a molecule on which an enzyme acts. In substrate-level phosphorylation, ADP and a phosphorylated metabolite are both substrates in the same enzymatic reaction. During the exergonic enzymatic reaction, the phosphate on the metabolite is transferred to ADP to form the products ATP and an unphosphorylated metabolite. Any ATP produced in a typical metabolic pathway is through substrate-level phosphorylation.
Oxidative phosphorylation, on the other hand, is specifically the addition of inorganic phosphate to ADP by ATP synthase powered by a proton gradient across a membrane. This almost always occurs in conjunction with an electron transport chain in respiration.
Figure \(\PageIndex{4}\): Substrate-level (top) and oxidative (bottom) phosphorylation (2021; Jeanne Kagle)
Making ATP Interactives
Substrate-Level Phosphorylation
Substrate-Level Versus Oxidative Phosphorylation
Exercise \(\PageIndex{3}\)
What is the function of an electron carrier?
Enzyme Structure and Function
A substance that helps speed up a chemical reaction is a catalyst. Catalysts are not used or changed during chemical reactions and, therefore, are reusable. Whereas inorganic molecules may serve as catalysts for a wide range of chemical reactions, proteins called enzymes serve as catalysts for biochemical reactions inside cells. Enzymes thus play an important role in controlling cellular metabolism.
An enzyme functions by lowering the activation energy of a chemical reaction inside the cell. Activation energy is the energy needed to form or break chemical bonds and convert reactants to products (Figure \(\PageIndex{5}\)). Enzymes lower the activation energy by binding to the reactant molecules and holding them in such a way as to speed up the reaction.
The chemical reactants to which an enzyme binds are called substrate s , and the location within the enzyme where the substrate binds is called the enzyme’s active site. The characteristics of the amino acids near the active site create a very specific chemical environment within the active site that induces suitability to binding, albeit briefly, to a specific substrate (or substrates). Due to this jigsaw puzzle-like match between an enzyme and its substrates, enzymes are known for their specificity. In fact, as an enzyme binds to its substrate(s), the enzyme structure changes slightly to find the best fit between the transition state (a structural intermediate between the substrate and product) and the active site, just as a rubber glove molds to a hand inserted into it. This active-site modification in the presence of substrate, along with the simultaneous formation of the transition state, is called induced fit (Figure \(\PageIndex{6}\)). Overall, there is a specifically matched enzyme for each substrate and, thus, for each chemical reaction; however, there is some flexibility as well. Some enzymes have the ability to act on several different structurally related substrates.
Enzymes are subject to influences by local environmental conditions such as pH, substrate concentration, and temperature. Although increasing the environmental temperature generally increases reaction rates, enzyme catalyzed or otherwise, increasing or decreasing the temperature outside of an optimal range can affect chemical bonds within the active site, making them less well suited to bind substrates. High temperatures will eventually cause enzymes, like other biological molecules, to denature, losing their three-dimensional structure and function. Enzymes are also suited to function best within a certain pH range, and, as with temperature, extreme environmental pH values (acidic or basic) can cause enzymes to denature. Active-site amino-acid side chains have their own acidic or basic properties that are optimal for catalysis and, therefore, are sensitive to changes in pH.
Another factor that influences enzyme activity is substrate concentration: Enzyme activity is increased at higher concentrations of substrate until it reaches a saturation point at which the enzyme can bind no additional substrate. Overall, enzymes are optimized to work best under the environmental conditions in which the organisms that produce them live. For example, while microbes that inhabit hot springs have enzymes that work best at high temperatures, human pathogens have enzymes that work best at 37°C. Similarly, while enzymes produced by most organisms work best at a neutral pH, microbes growing in acidic environments make enzymes optimized to low pH conditions, allowing for their growth at those conditions.
Many enzymes do not work optimally, or even at all, unless bound to other specific nonprotein helper molecules, either temporarily through ionic or hydrogen bonds or permanently through stronger covalent bonds. Binding to these molecules promotes optimal conformation and function for their respective enzymes. Two types of helper molecules are cofactors and coenzymes. Cofactors are inorganic ions such as iron (Fe 2 + ) and magnesium (Mg 2 + ) that help stabilize enzyme conformation and function. One example of an enzyme that requires a metal ion as a cofactor is the enzyme that builds DNA molecules, DNA polymerase, which requires a bound zinc ion (Zn 2 + ) to function.
Coenzymes are organic helper molecules that are required for enzyme action. Like enzymes, they are not consumed and, hence, are reusable. The most common sources of coenzymes are dietary vitamins. Some vitamins are precursors to coenzymes and others act directly as coenzymes.
Some cofactors and coenzymes, like coenzyme A (CoA), often bind to the enzyme’s active site, aiding in the chemistry of the transition of a substrate to a product (Figure \(\PageIndex{7}\)). In such cases, an enzyme lacking a necessary cofactor or coenzyme is called an apoenzyme and is inactive. Conversely, an enzyme with the necessary associated cofactor or coenzyme is called a holoenzyme and is active. NADH and ATP are also both examples of commonly used coenzymes that provide high-energy electrons or phosphate groups, respectively, which bind to enzymes, thereby activating them.
Exercise \(\PageIndex{4}\)
What role do enzymes play in a chemical reaction?
Key Concepts and Summary
- Metabolism includes chemical reactions that break down complex molecules ( catabolism ) and those that build complex molecules ( anabolism ).
- Organisms may be classified according to their source of carbon. Autotrophs convert inorganic carbon dioxide into organic carbon; heterotrophs use fixed organic carbon compounds.
- Organisms may also be classified according to their energy source. Phototrophs obtain their energy from light. Chemotrophs get their energy from chemical compounds. Organotrophs use organic molecules, and lithotrophs use inorganic chemicals.
- Cellular electron carriers accept high-energy electrons from foods and later serve as electron donors in subsequent redox reactions . FAD/FADH 2 , NAD + /NADH , and NADP + /NADPH are important electron carriers.
- Adenosine triphosphate (ATP) serves as the energy currency of the cell, safely storing chemical energy in its two high-energy phosphate bonds for later use to drive processes requiring energy.
- Enzymes are biological catalysts that increase the rate of chemical reactions inside cells by lowering the activation energy required for the reaction to proceed.
- In nature, exergonic reactions do not require energy beyond activation energy to proceed, and they release energy. They may proceed without enzymes, but at a slow rate. Conversely, endergonic reactions require energy beyond activation energy to occur. In cells, endergonic reactions are coupled to exergonic reactions, making the combination energetically favorable.
- Substrates bind to the enzyme’s active site . This process typically alters the structures of both the active site and the substrate, favoring transition-state formation; this is known as induced fit .
- Cofactors are inorganic ions that stabilize enzyme conformation and function. Coenzymes are organic molecules required for proper enzyme function and are often derived from vitamins. An enzyme lacking a cofactor or coenzyme is an apoenzyme; an enzyme with a bound cofactor or coenzyme is a holoenzyme .
Contributors and Attributions
-
Nina Parker, (Shenandoah University), Mark Schneegurt (Wichita State University), Anh-Hue Thi Tu (Georgia Southwestern State University), Philip Lister (Central New Mexico Community College), and Brian M. Forster (Saint Joseph’s University) with many contributing authors. Original content via Openstax (CC BY 4.0; Access for free at https://openstax.org/books/microbiology/pages/1-introduction )


3.4: Body Mechanics and Safe Equipment Use
In addition to promoting safety for patients and their families, it is important for health care workers to be aware of safety risks in the environment and to take measures to protect themselves. Common safety risks to health care workers include sharps injuries, exposure to blood-borne pathogens, lack of personal protective equipment, and lifting injuries. A sharps injury is a penetrating wound from a needle, scalpel, or other sharp object that may result in exposure to blood-borne pathogens. Blood-borne pathogens are pathogenic microorganisms present in blood and body fluids that can cause disease such as hepatitis B (HBV) and human immunodeficiency virus (HIV). Personal protective equipment (PPE) is used to prevent transmission of blood-borne pathogens and infection and includes gloves, masks, goggles, gowns, and other types of protective equipment. This section will focus on lifting injuries related to moving clients, and the other safety risks will be discussed in Chapter 4 .
The health and well-being of nurse aides is directly related to the quality of care residents receive. When a health care worker is injured, they may be unable to provide care to the extent required by residents. With this in mind, it is vital for nursing assistants to know how to prevent injury in the workplace. An article published in the 2018 International Journal of Environmental Research and Public Health noted that 88% of nurse aides reported at least one of their body parts having a work-related musculoskeletal symptoms (WRMS) . [1] The lower back was the most commonly affected WRMS area, followed by the arms and shoulders. According to this study, nursing assistants ranked first for occupational-related back sprains and strains, above construction workers, garbage collectors, and other health care workers. WRMS reported by nurse aides account for over 50% of all musculoskeletal injuries reported in the United States. These injuries are attributed to manual handling of clients, lifting heavy physical loads, assuming frequent awkward positions, and performing repetitive movements. [2]
Using gait belts and mechanical lifts for transferring residents from one location to another, such as from the bed to a wheelchair or a wheelchair to the toilet, has greatly reduced the risk of lifting injuries to both residents and aides. These transferring techniques will be discussed in Chapter 8 .
Lifting injuries can also occur when repositioning residents while they are in bed. Repositioning is frequently performed for residents to provide hygiene, alleviate pain, or prevent skin breakdown. The ABC mnemonic for using proper body mechanics when transferring or repositioning residents stands for A lignment, B ase of support, and C enter of gravity [3] :
-
Alignment:
Correct body alignment is also referred to as good posture. When standing up straight, an imaginary line should be able to be drawn straight down through the center of the body so that both sides of the body are mirror images of each other. Body parts should be lined up naturally, with arms at one’s side, palms directed forward, and feet pointed forward and slightly apart. Follow these guidelines to use proper alignment to prevent lifting injuries:
- Maintain correct body alignment when lifting or carrying an object.
- Keep the object close to your body, unless close proximity could transmit pathogens.
- Point your feet and body in the direction you are moving.
- Do not twist at the waist.
- Base of support: Creating a good base of support improves your balance, whereas imbalance creates awkward positioning that can lead to injury. To create a strong base of support, place your feet about shoulder width apart or just slightly wider than your hips.
- Center of gravity: A person’s center of gravity is where most of one’s weight is concentrated. When standing, the pelvis is the center of gravity. Maintaining a low center of gravity provides a stable base of support and improves balance.
For example, when lifting objects or people, keep your center of gravity low with a good base of support by bending at the knees with the feet shoulder width apart. Keep in mind that your center of gravity also includes the resident or the object, so keep them as close to your body as possible. To maintain good alignment, face the person or object you are moving and use both sides of your body equally. Figure 3.7 [4] illustrates safer body mechanics in Option “C” by maintaining good alignment, establishing a base of support, and keeping the load close and near to one’s center of gravity while bending the knees.
Facilities have specialized equipment used to assist in lifting and transferring clients that significantly reduces the risk of lifting injuries. Manufacturers provide specific instructions for the safe use and maintenance of their equipment. Be certain that you receive extensive training on safely using this equipment during your orientation to the facility. Orientation to lifting equipment should include becoming familiar with all parts of the device, the requirements for the mobility status of residents who will use that device, and potential risks to residents and caregivers while using the device. See Figure 3.8 [5] for an image of lifting equipment.
For additional information on OSHA regulations for using lifting equipment and preventing lifting injuries, refer to this document: Guidelines for Nursing Homes PDF.
- Cheung, K., Szeto, G., Lai, G., & Ching, S. (2018). Prevalence of and factors associated with work-related musculoskeletal symptoms in nursing assistants working in nursing homes. International Journal of Environmental Research and Public Health, 15 (2), 265. https://doi.org/10.3390/ijerph15020265 ↵
- Cheung, K., Szeto, G., Lai, G., & Ching, S. (2018). Prevalence of and factors associated with work-related musculoskeletal symptoms in nursing assistants working in nursing homes. International Journal of Environmental Research and Public Health, 15 (2), 265. https://doi.org/10.3390/ijerph15020265 ↵
- North Carolina Department of Health and Human Services. (2019). State-approved curriculum: Nurse aide I Training program. https://info.ncdhhs.gov/dhsr/hcpr/curriculum/pdf/moduleI.pdf ↵
- “ Centre_of_Gravity.png ” by Glynda Rees Doyle and Jodie Anita McCutcheon is licensed under CC BY 4.0. Access for free at https://opentextbc.ca/clinicalskills/chapter/3-2-body-mechanics/ ↵
- “ User-Integra-lifter1.jpg ” by Integracp is licensed under CC BY-SA 3.0 ↵


30.4: Chapter Summary
This chapter discussed gastrointestinal disturbances such as nausea, vomiting, motion sickness, constipation, and diarrhea, which are often symptoms of an underlying condition. While treatment of the GI symptom is a priority, providers should explore the potential causes of the symptoms. Antiemetics, antidiarrheals, and laxatives may only be temporary solutions until the primary cause is discovered and treated.
The text also noted that the GI system is vulnerable to fluid and electrolyte imbalances from GI disturbances as well as GI medications. Nurses must consistently assess GI status, the risk of dehydration, and electrolyte imbalances. Nurses should encourage clients to drink at least 2 liters of water a day, unless contraindicated, to promote a healthy GI tract and to optimize its proper functioning.


1.9: Inexact Numbers
Example:
\[\frac{1}{3}=(-1)^{0} \times \frac{1}{4} \times\left(1+\frac{1}{3}\right) \text {, } \nonumber \]
so that \(p=e-127=-2\) and \(e=125=128-3\) , or in binary, \(e=01111101\) . How is \(f=1 / 3\) represented in binary? To compute binary number, multiply successively by 2 as follows:
\(\begin{array}{lr}0.333 \ldots & 0 . \\ 0.666 \ldots & 0.0 \\ 1.333 \ldots & 0.01 \\ 0.666 \ldots & 0.010 \\ 1.333 \ldots & 0.0101 \\ \text { etc. } & \end{array}\)
so that \(1 / 3\) exactly in binary is \(0.010101 \ldots\) With only 23 bits to represent \(f\) , the number is inexact and we have
\[f=01010101010101010101011 \nonumber \]
where we have rounded to the nearest binary number (here, rounded up). The machine number \(1 / 3\) is then represented as
\[00111110101010101010101010101011 \nonumber \]
or in hex
\[\text { Зeaaaaab. } \nonumber \]
Find smallest positive integer that is not exact in single pre- cision
Let \(N\) be the smallest positive integer that is not exact. Now, I claim that
\[N-2=2^{23} \times 1.11 \ldots 1 \nonumber \]
and
\[N-1=2^{24} \times 1.00 \ldots 0 \nonumber \]
The integer \(N\) would then require a one-bit in the \(2^{-24}\) position, which is not available. Therefore, the smallest positive integer that is not exact is \(2^{24}+1=16777217\) . In MATLAB, single \(\left(2^{24}\right)\) has the same value as single \(\left(2^{24}+1\right) .\) Since single \(\left(2^{24}+1\right)\) is exactly halfway between the two consecutive machine numbers \(2^{24}\) and \(2^{24}+2\) , MATLAB rounds to the number with a final zero-bit in \(f\) , which is \(2^{24} .\)


3.3: The Meaning of Statements
Have you ever taken standardized tests where they give you the first few terms of a sequence and then ask you for the next one? Here are some sample questions. In each case, see if you can determine a reasonable answer for the next term.
- \(2,5,8,11,14,17,20,23,26,...\)
- \(1,1,2,3,5,8,13,21,34,55,89,144,233,377,...\)
- \(1,2,5,14,42,132,429,1430,4862,...\)
- \(2,6,12,20,30,42,56,72,90,110,...\)
- \(2,3,6,11,18,27,38,51,...\)
Pretty easy stuff! OK, now try the following somewhat more challenging sequence. Here, we'll give you a lot more terms and challenge you to find the next one.
\(1,2,3,4,1,2,3,4,5,1,2,3,4,5,2,3,4,5,6,2,3,4,5,6,1,2,3,4,5,2,3,4,5,6,…\)
Trust us when we say that we really have in mind something very concrete, and once it's explained, you'll agree that it's “obvious.” But for now, it's far from it.
Here's another danger lurking around the corner when we encounter formulas like
\(1+2+3+ \cdot \cdot \cdot +n = \dfrac{n(n+1)}{2}\).
What do the dots in this statement mean? In fact, let's consider a much simpler question. What is meant by the following expression:
\(1+2+3+\cdot \cdot \cdot +6\)
Are we talking about the sum of the first six positive integers, or are we talking about the sum of the first 19 terms from the more complicated challenge sequence given above? You are supposed to answer that you don't know, and that's the correct answer.
The point here is that without a clarifying comment or two, the notation \(1+2+3+\cdot \cdot \cdot+6\) isn't precisely defined. Let's see how to make things right.
First, let \(f: \mathbb{N} \rightarrow \mathbb{N}\) be a function. Set
\(\displaystyle \sum_{i=1}^1 f(i) = f(1)\)
and if \(n > 1\), define
\(\displaystyle \sum_{i=1}^n f(i) = f(n) + \displaystyle \sum_{i=1}^{n-1} f(i)\)
To see that these two statements imply that the expression \(\sum_{i=1}^n f(i)\) is defined for all positive integers, apply the Well Ordered Property to the set of all positive integers for which the expression is not defined and use the recursive definition to define it for the least element.
So if we want to talk about the sum of the first six positive integers, then we should write:
\(\displaystyle \sum_{i=1}^6 i\)
Now it is clear that we are talking about a computation that yields 21 as an answer.
A second example: previously, we defined \(n!\) by writing
\(n! = n \times (n-1) \times (n-2) \times \cdot \cdot \cdot \times 3 \times 2 \times 1\)
By this point, you should realize that there's a problem here. Multiplication, like addition, is a binary operation. And what do those dots mean? Here's a way to do the job more precisely. Define \(n!\) to be 1 if \(n=1\). And when \(n>1\), set \(n! = n(n-1)!\).
Definitions like these are called recursive definitions . They can be made with different starting points. For example, we could have set \(n! = 1\) when \(n=0\), and when \(n > 0\), set \(n! = n(n-1)!\).
Here's a code snippet in SageMath, which is based on Python, so this also works as Python code.
//Code
What is the value of
sumrecursive(4)
? (In order to make sure you understand how this recursive function works, calculate out
sumrecursive(4)
should be by hand before modifying the SageMath cell above.) Does it make sense to say that
sumrecursive(n)
is defined for all positive integers \(n\)? Did you recognize that this program provides a precise meaning to the expression:
\(2 + 3 + 6 + 11 + 18 + 27 + 38 + 51 + \cdot \cdot \cdot + (n^2 - 2n + 3)\)


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Abruption
: Premature separation of the placenta from the wall of the womb
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Amnion
: An embryonic membrane that encircles a developing fetus and contains amniotic fluid.
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Amniocentesis
: A procedure in which a small sample of amniotic fluid is removed from around the fetus
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Amniotic fluid
: The fluid surrounding the fetus
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Amniotomy
: (artificial rupture of membranes, ARM) Breaking the membranes using a special plastic hook
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Anemia
: Lack of hemoglobin in red blood cells, due to iron deficiency or disease
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Antepartum Hemorrhage
: (APH) Vaginal bleeding that happens after 24 weeks of pregnancy and before delivery
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Breech
: The baby is lying bottom down in the womb
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Celiac sprue
: Nutrient absorption impairment which is improved when gluten is removed from the diet. Characteristic mucosal lesion of the small intestine.
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Cephalic
: The baby is lying head down in the womb
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Chorion
: The embryonic membrane that forms the outermost covering around the developing fetus.
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Chorionic Villus Sampling
: (CVS) A method for sampling placental tissue for genetic or chromosome studies.
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Colostrum:
the fluid that is made late in pregnancy and the first few days postpartum in the breast that contains immunologic substances and essential nutrients.
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Cleavage
: The early successive divisions of embryonic cells into smaller and smaller cells.
  Sperm then propel themselves into the fallopian tubes where fertilization may occur if an ovum is present.
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Crohn's disease
: Skip lesions in the colon and is a malabsorptive disease.
-
Cystitis
: Infection of the bladder
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Dizygous
: Not identical (fraternal) twins
-
Doppler
: A form of ultrasound used specially to investigate blood flow in the placenta or in the fetus
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Down Syndrome
: (Trisomy 21) A disorder caused by the presence of an extra chromosome 21 in the cells
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Ectopic Pregnancy
: A pregnancy that develops outside of the womb
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Edema
: Swelling of the fingers, legs, toes, and face.
-
Embryo
: The medical term for the baby from conception to about six weeks
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Engagement
: The process in which the head of the baby moves down from high in the mother's abdomen and settles deeper into her pelvis in preparation for birth. This can happen any time between 36 weeks and labor.
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Epidural Anesthesia
: A method of numbing the nerves of the lower spinal cord to ensure a pain-free labor
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Episiotomy
: A cut of the perineum and vagina performed to make the delivery easier
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External Fetal Monitor
: An electronic monitor used to record the fetal heartbeat and mother’s contractions
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Fallopian Tubes
: (uterine tubes) Two tubular structures (one on each side of the womb) leading from the ovaries to the uterus
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Fertilization
: The union of an egg cell and a sperm cell is present wherein 23 chromosomes from each parent come together to form a zygote. After sperm penetrates, the ovum undergoes a chemical change to prevent other sperm from entering. Multiple births can occur from complete division of the conceptus during early cleavage or from fertilization of multiple ova. Birth control techniques are designed to prevent ovulation or to prevent fertilization by barriers that keep sperm and ova separated.
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Fetus
: Medical term for the baby from six weeks after conception until birth
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Forceps
: Metal instruments that fit on either side of the baby's head and are used to help deliver the baby
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Fundus
: The top of the womb
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Germ layer
: Layers of cells within an embryo that form the body organs during development.
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Glial Cells
(neuroglia; glia): Non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin, and participate in signal transmission in the nervous system. In the human brain, glia are estimated to outnumber neurons by about 10 to 1. Glial cells provide support and protection for neurons, the other main type of cell in the central nervous system. They are thus known as the "glue" of the nervous system. The four main functions of glial cells are to surround neurons and hold them in place, to supply nutrients and oxygen to neurons, to insulate one neuron from another, and to destroy pathogens and remove dead neurons.
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Hemoglobin
: (Hb)The oxygen carrying constituent of red blood cells
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Induction of labor
: (IOL) the procedure for initiating labor artificially
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In utero death
: (IUD)the death of the unborn fetus after 24 weeks
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In vitro fertilization
: (IVF) a method of assisted conception in which fertilization occurs outside the mother's and the embryo is replaced in the womb
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Lanugo
: fine hair that covers the fetus in the womb
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Lochia
: blood loss after birth
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Mastitis
inflammation of the breast most frequently in lactation.
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Neonatal
: baby less than 28 days old
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Nuchal scan
: special ultrasound scan that gives an estimate of the risk of Down syndrome
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Oocyte
: one ovum that is released from the ovary at each ovulation
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Placenta
: The structure by which an unborn child is attached to its mother's uterine wall and through which it is nourished.
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Postnatal
: After birth
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Prenatal
: Before birth
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Quickening
: The process that occurs between the seventeenth and twentieth weeks of fetal development, the fetus's leg bones achieve their final relative proportions. In this process the muscles contract, causing movement at the fetus's synovial joints. The joint movement enhances the nutrition of the articular cartilage and prevents the fusion of connective tissues within the joint. It also promotes bone hardening. It is this stage, where the fetus's bones become more developed and harder, that the mother begins to notice fetal movement.
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Rudimentary
: Basic; minimal; with less than, or only the minimum, necessary
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Thrush
: Creamy white flakes on a red papillae on tongue and tongue may be enlarged.
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Umbilical cord
: The cord-like structure that connects the fetus to the placenta.
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Zygote
: A cell produced by the fusion of an egg and a sperm; a fertilized egg cell