Pharynx Epiglottis Trachea

Define essential nutrient.

List some common sources of carbohydrates.

Summarize the importance of cellulose in the diet.

Explain what happens to excess glucose in the body.

Explain why a temporary drop in the blood glucose concentration may impair nervous system functioning.

List some of the factors that affect an individual's need for carbohydrates.

Define triglyceride.

List some common sources of lipids.

Define beta oxidation.

Explain how fats may provide energy.

Describe the liver's role in fat metabolism.

Discuss the functions of cholesterol.

Define deamination, and explain its importance.

List some common sources of protein.

Distinguish between essential and nonessential amino acids.

Explain why all of the essential amino acids must be present before growth can occur.

Distinguish between complete and incomplete proteins. Review the major functions of amino acids. Define nitrogen balance.

Explain why a protein deficiency may be accompanied by edema.

Define calorie.

Explain how the caloric values of foods are determined.

Define basal metabolic rate.

List some of the factors that affect the BMR.

Define energy balance.

26. Explain what is meant by desirable weight.

27. Distinguish between overweight and obesity.

28. Discuss the general characteristics of fat-soluble vitamins.

29. List the fat-soluble vitamins, and describe the major functions of each vitamin.

30. List some good sources for each of the fat-soluble vitamins.

31. Explain what is meant by the vitamin B complex.

32. List the water-soluble vitamins, and describe the major functions of each vitamin.

33. List some good sources for each of the water-soluble vitamins.

34. Discuss the general characteristics of the mineral nutrients.

35. List the major minerals, and describe the major functions of each mineral.

36. List some good sources for each of the major minerals.

37. Distinguish between a major mineral and a trace element.

38. List the trace elements, and describe the major functions of each trace element.

39. List some good sources of each of the trace elements.

40. Define adequate diet.

41. Define malnutrition.

42. Distinguish between primary and secondary malnutrition.

43. Discuss bodily changes during starvation.

44. Distinguish among marasmus, kwashiorkor, anorexia nervosa, and bulimia.

45. Describe some medical conditions that affect the ability to obtain adequate nutrition as a person ages.

Person Afect Kwashiokor

m understanding ^Vo rds alveol-, small cavity: alveolus— microscopic air sac within a lung.

bronch-, windpipe: bronchus— primary branch of the trachea. carcin-, spreading sore:

carcinoma—type of cancer. carin-, keel-like: carina—ridge of cartilage between the right and left bronchi. cric-, ring: cricoid cartilage— ring-shaped mass of cartilage at the base of the larynx.

epi-, upon: epiglottis—flaplike structure that partially covers the opening into the larynx during swallowing. hem-, blood: hemoglobin—

pigment in red blood cells. inhal-, to breathe in:

inhalation—to take air into the lungs. phren-, mind, diaphragm: phrenic nerve—nerve associated with the cervical plexuses that stimulate the muscle fibers of the diaphragm to contract. tuber-, swelling: tuberculosis— disease characterized by the formation of fibrous masses within the lungs.

chapter objectives

After you have studied this chapter, you should be able to

1. List the general functions of the respiratory system.

2. Name and describe the locations of the organs of the respiratory system.

3. Describe the functions of each organ of the respiratory system.

4. Explain how inspiration and expiration are accomplished.

5. Name and define each of the respiratory air volumes and capacities.

6. Explain how the alveolar ventilation rate is calculated.

7. List several nonrespiratory air movements and explain how each occurs.

8. Locate the respiratory center and explain how it controls normal breathing.

9. Discuss how various factors affect the respiratory center.

10. Describe the structure and function of the respiratory membrane.

11. Explain how the blood transports oxygen and carbon dioxide.

12. Describe the effects of aging on the respiratory system.

Epiglottis Malfunction

Detecting the colorless, odorless gas carbon monoxide can be lifesaving, because this molecule prevents hemoglobin from adequately binding oxygen. Carbon monoxide is produced from the incomplete combustion of carbon-containing fuels. Common culprits include wood stoves, kerosene heaters, gasoline engines, blocked chimneys, malfunctioning fireplaces, faulty ice-resurfacing machines, gas-powered equipment used in poorly ventilated warehouses and garages, and even indoor tractor pulls.

seventy-eight-year-old man arrived in the emergency

A department reporting chest pain, shortness of breath, and fatigue. He was confused and upset, with an irregular pulse, fast respirations, and abnormal heart rhythm. Physicians treated the man with oxygen, aspirin, and nitroglycerin, suspecting a heart condition. Then they noticed that his wife lay on a nearby stretcher, complaining of the same symptoms! The woman said that her symptoms had begun two hours after her husband fell ill. Her chest pain had begun in her left arm and intensified as she served him tea. She, too, was treated as if she had suffered heart damage. But the doctors were puzzled.

The couple was admitted to the hospital, even though their symptoms improved after spending two hours in the emergency department. They felt well when they returned to their apartment two days later but in another two days, returned to the hospital, reporting the same symptoms. This time, medical workers suspected that something in their home environment was causing the symptoms. They were right.

Upon questioning, the couple mentioned that they had spent the winter in a small, unventilated apartment that was heated by two kerosene space heaters. The source of their medical problem became clear—carbon monoxide (CO) poisoning. This colorless, odorless gas was binding to their hemoglobin molecules, robbing tissues of their oxygen supply. But the man and woman were lucky to have developed symptoms suggestive of heart failure, because it sent them back to the hospital for help. They could have easily fallen unconscious, gone into a coma, and died. CO poisoning is known as "the great imitator," because its symptoms are easily attributed to other causes.

Detecting the colorless, odorless gas carbon monoxide can be lifesaving, because this molecule prevents hemoglobin from adequately binding oxygen. Carbon monoxide is produced from the incomplete combustion of carbon-containing fuels. Common culprits include wood stoves, kerosene heaters, gasoline engines, blocked chimneys, malfunctioning fireplaces, faulty ice-resurfacing machines, gas-powered equipment used in poorly ventilated warehouses and garages, and even indoor tractor pulls.

The respiratory system consists of a group of passages that filter incoming air and transport it into the body, into the lungs, and to the many microscopic air sacs where gases are exchanged. The entire process of exchanging gases between the atmosphere and body cells is called respiration (res"pi-ra'shun). It involves several events:

• Movement of air in and out of the lungs, commonly called breathing or ventilation.

• Exchange of gases between the air in the lungs and the blood, sometimes called external respiration.

• Transport of gases by the blood between the lungs and body cells.

• Exchange of gases between the blood and the body cells, sometimes called internal respiration.

• Oxygen utilization and production of carbon dioxide by body cells is part of the process of cellular respiration.

Why We Breathe

Respiration occurs on a macroscopic level—a function provided by an organ system. However, the reason that body cells must exchange gases—that is, take up oxygen and rid themselves of carbon dioxide—is apparent at the cellular and molecular levels.

OO Reconnect to chapter 4, Aerobic Respiration, page 117

Respiration enables cells to harness the energy held in the chemical bonds of nutrient molecules. Recall that energy is slowly liberated from food molecules by stripping off electrons and channeling them through a series of electron carriers. Without oxygen as a final electron acceptor, much energy remains locked in nutrient molecules. Recall also that in the reactions that remove electrons, carbons are cleaved, combined with oxygen, and released as carbon dioxide (CO2), a metabolic waste. Just as oxygen is required for cellular respiration, carbon dioxide, by combining with water to form carbonic acid, contributes to blood pH. However, too much CO2 will lower blood pH, threatening homeostasis. Cellular respiration and control of blood pH, then, explain why we must obtain oxygen and get rid of carbon dioxide.

Organs of the Respiratory System

Soft palate

The organs of the respiratory system can be divided into two groups, or tracts. Those in the upper respiratory tract include the nose, nasal cavity, sinuses, and pharynx. Those in the lower respiratory tract include the larynx, trachea, bronchial tree, and lungs (fig. 19.1).


The nose is covered with skin and is supported internally by muscle, bone, and cartilage. Its two nostrils (external nares) provide openings through which air can enter and leave the nasal cavity. Many internal hairs guard these openings, preventing entry of large particles carried in the air.

Nasal Cavity

The nasal cavity, a hollow space behind the nose, is divided medially into right and left portions by the nasal septum. This cavity is separated from the cranial cavity by the cribriform plate of the ethmoid bone and from the oral cavity by the hard palate.

The nasal septum may bend during birth or shortly before adolescence. Such a deviated septum may obstruct the nasal cavity, making breathing difficult.

As figure 19.2 shows, nasal conchae (turbinate bones) curl out from the lateral walls of the nasal cavity on each side, dividing the cavity into passageways called the superior, middle, and inferior meatuses (see chapter 7, p. 219). They also support the mucous membrane that lines the nasal cavity and help increase its surface area.

The upper posterior portion of the nasal cavity, below the cribriform plate, is slitlike, and its lining contains the olfactory receptors that provide the sense of smell. The remainder of the cavity conducts air to and from the nasopharynx.

The mucous membrane lining the nasal cavity contains pseudostratified ciliated epithelium that is rich in mucus-secreting goblet cells (see chapter 5, p. 144). It also includes an extensive network of blood vessels and normally appears pinkish. As air passes over the membrane, heat radiates from the blood and warms the air, adjusting its temperature to that of the body. In addition, evaporation of water from the mucous lining moistens the air.

Oral cavity


Pharynx Epiglottis Esophagus

Soft palate

Pharynx Epiglottis Esophagus

Buccal Cavity Pharynx Epiglottis

Oral cavity

Figure 19.1

Organs of the respiratory system.

Figure 19.1

Organs of the respiratory system.

The sticky mucus the mucous membrane secretes entraps dust and other small particles entering with the air.

As the cilia of the epithelial cells move, a thin layer of mucus and any entrapped particles are pushed toward the pharynx (fig. 19.3). When the mucus reaches the pharynx, it is swallowed. In the stomach, gastric juice is likely to destroy microorganisms in the mucus, including disease-causing forms. Thus, the filtering that the mucous membrane provides not only prevents particles from reaching the lower air passages, but also helps prevent respiratory infections. Clinical Application 19.1 discusses how cigarette smoking impairs the respiratory system, beginning with the cleansing mucus and cilia.

D What is respiration?

Which organs constitute the respiratory system?

What is the function of the mucous membrane that lines the nasal cavity?

What is the function of the cilia on the cells that line the nasal cavity?

Figure 19.2

Major features of the upper respiratory tract.

Anatomy The Upper Respiratory Tract

Figure 19.2

Major features of the upper respiratory tract.

Picture Cilia Mucus Nose


Cilia move mucus and trapped particles from the nasal cavity to the pharynx.


Cilia move mucus and trapped particles from the nasal cavity to the pharynx.


Recall from chapter 7 (p. 220) that the sinuses (paranasal sinuses) are air-filled spaces located within the maxillary, frontal, ethmoid, and sphenoid bones of the skull (fig. 19.4). These spaces open into the nasal cavity and are lined with mucous membranes that are continuous with the lining of the nasal cavity. Consequently, mucus secretions drain from the sinuses into the nasal cavity. Membranes that are inflamed and swollen because of nasal infections or allergic reactions (sinusitis) may block this drainage, increasing pressure within a sinus and causing headache.

The sinuses reduce the weight of the skull. They also serve as resonant chambers that affect the quality of the voice.

It is possible to illuminate a person's frontal sinus in a darkened room by holding a small flashlight just beneath the eyebrow. Similarly, holding the flashlight in the mouth illuminates the maxillary sinuses.

U Where are the sinuses located?

What are the functions of the sinuses?


The pharynx (throat) is located posterior to the oral cavity and between the nasal cavity and the larynx. It is a passageway for food moving from the oral cavity to the esophagus and for air passing between the nasal cavity and the larynx (see fig. 19.2). It also aids in producing the sounds of speech. The subdivisions of the pharynx— the nasopharynx, oropharynx, and laryngopharynx—are described in chapter 17 (p. 695).

The Effects of Cigarette Smoking on the Respiratory System

Damage to the respiratory system from cigarette smoking is slow, progressive, and deadly. A healthy respiratory system is continuously cleansed. The mucus produced by the respiratory tubules traps dirt and disease-causing organisms, which cilia sweep toward the mouth, where they can be eliminated. Smoking greatly impairs this housekeeping. With the very first inhalation of smoke, the beating of the cilia slows. With time, the cilia become paralyzed and, eventually, disappear altogether. The loss of cilia leads to the development of smoker's cough. The cilia no longer effectively remove mucus, so the individual must cough it up. Coughing is usually worse in the morning because mucus has accumulated during sleep.

To make matters worse, excess mucus is produced and accumulates, clogging the air passageways. Pathogenic organisms that are normally removed now have easier access to the respiratory surfaces, and the resulting lung congestion favors their growth. This is why smokers are sick more often than nonsmokers. In addition, a lethal chain reaction begins. Smoker's cough leads to chronic bronchitis, caused by destroyed respiratory cilia. Mucus production increases and the lining of the bronchioles thickens, making breathing difficult. The bronchioles lose elasticity and are no longer able to absorb the pressure changes accompanying coughing. As a result, a cough can increase the air pressure within the alveoli (microscopic air sacs) enough to rupture the delicate alveolar walls; this condition is the hallmark of smoking-

induced emphysema. The burst alveoli cause worsening of the cough, fatigue, wheezing, and impaired breathing. Emphysema is fifteen times more common among individuals who smoke a pack of cigarettes a day than among nonsmokers.

Simultaneous with the structural changes progressing to emphysema may be cellular changes leading to lung cancer. First, cells in the outer border of the bronchial lining begin to divide more rapidly than usual. Eventually, these cells displace the ciliated cells. Their nuclei begin to resemble those of cancerous cells — large and distorted with abnormal numbers of chromosomes. Up to this point, the damage can be repaired if smoking ceases. If smoking continues, these cells may eventually break through the basement membrane and begin dividing within the lung tissue, forming a tumor with the potential of spreading throughout lung tissue (figs. 19A and 19B) and


The larynx is an enlargement in the airway superior to the trachea and inferior to the pharynx. It is a passageway for air moving in and out of the trachea and prevents foreign objects from entering the trachea. The larynx also houses the vocal cords (see reference plates 49 and 71).

The larynx is composed of a framework of muscles and cartilages bound by elastic tissue. The largest of the cartilages are the thyroid, cricoid, and epiglottic cartilages (fig. 19.5). These structures are single. The other laryngeal cartilages—the arytenoid, corniculate, and cuneiform cartilages—are paired.

The thyroid cartilage was named for the thyroid gland that covers its lower area. This cartilage is the shieldlike structure that protrudes in the front of the neck and is sometimes called the Adam's apple. The protrusion typically is more prominent in males than in fe males because of an effect of male sex hormones on the development of the larynx.

The cricoid cartilage lies inferior to the thyroid cartilage. It marks the lowermost portion of the larynx.

The epiglottic cartilage, the only one of the laryn-geal cartilages that is elastic, not hyaline, cartilage, is attached to the upper border of the thyroid cartilage and supports a flaplike structure called the epiglottis. The epiglottis usually stands upright and allows air to enter the larynx. During swallowing, however, muscular contractions raise the larynx, and the base of the tongue presses the epiglottis downward. As a result, the epiglottis partially covers the opening into the larynx, helping prevent foods and liquids from entering the air passages.

The pyramid-shaped arytenoid cartilages are located superior to and on either side of the cricoid cartilage. Attached to the tips of the arytenoid cartilages are beyond, such as to the brain or bones. Eighty percent of lung cancer cases are due to cigarette smoking. Only 13% of lung cancer patients live as long as five years after the initial diagnosis.

It pays to quit. Much of the damage to the respiratory system can be repaired. Cilia are restored, and the thickening of alveolar walls due to emphysema can be reversed. But ruptured alveoli are gone forever. The nicotine in tobacco smoke causes a powerful dependency by binding to certain receptors on brain cells. ■

Normal lung tissue

Cancerous lung tissue

Normal lung tissue

Cancerous lung tissue

Blood Vessel Tumor
Epiglottis Cancer


Lung cancer may begin as a tiny tumor growing in an alveolus, a microscopic air sac (125x).


The lung on the left is healthy. A cancerous tumor has invaded the lung on the right, taking up nearly half of the lung space.

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  • lara cocci
    What happens when the blood vessels in trachea burst?
    2 years ago
  • Jasmine
    Where is thebuccal cavity?
    3 months ago

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