Chapter 8 | The Respiratory System

  1. Figure 8.7 Which of the following statements about the mammalian respiratory system is false?
    1. When we breathe in, air travels from the pharynx to the trachea.
    2. The bronchioles branch into bronchi.
    3. Alveolar ducts connect to alveolar sacs.
    4. Gas exchange between the lung and blood takes place in the alveolus.
      The illustration shows the flow of air through the human respiratory system. The nasal cavity is a wide cavity above and behind the nostrils, and the pharynx is the passageway behind the mouth. The nasal cavity and pharynx join and enter the trachea through the larynx. The larynx is somewhat wider than the trachea and flat. The trachea has concentric, ring-like grooves, giving it a bumpy appearance. The trachea bifurcates into two primary bronchi, which are also grooved. The primary bronchi enter the lungs, and branch into secondary bronchi. The secondary bronchi in turn branch into many tertiary bronchi. The tertiary bronchi branch into bronchioles, which branch into terminal bronchioles. Each terminal bronchiole ends in an alveolar sac. Each alveolar sac contains many alveoli clustered together, like bunches of grapes. The alveolar duct is the air passage into the alveolar sac. The alveoli are hollow, and air empties into them. Pulmonary arteries bring deoxygenated blood to the alveolar sac (and thus appear blue), and pulmonary veins return oxygenated blood (and thus appear red) to the heart. Capillaries form a web around each alveolus. The diaphragm is a membrane that pushes up against the lungs.
      Figure 8.7 Air enters the respiratory system through the nasal cavity and pharynx, and then passes through the trachea and into the bronchi, which bring air into the lungs. (credit: modification of work by NCI)
  2. Figure 8.13 Which of the following statements is false?
    1. In the tissues, PO2 drops as blood passes from the arteries to the veins, while PCO 2 increases.
    2. Blood travels from the lungs to the heart to body tissues, then back to the heart, then the lungs.
    3. Blood travels from the lungs to the heart to body tissues, then back to the lungs, then the heart.
    4. PO2 is higher in air than in the lungs.
      The illustration shows the movement of deoxygenated air into the lungs, and oxygenated air out of the lungs. Also shown is the circulation of blood through the body. Circulation begins when deoxygenated blood in arteries leaves the right side of the heart and enters the lungs. Oxygenated blood exits the lungs, and enters the left side of the heart, which pumps it to the rest of the body via arteries. The partial pressure of oxygen in the atmosphere is 160 millimeters of mercury, and the partial pressure of carbon dioxide is 0.2 millimeters of mercury. The partial pressure of oxygen in the arteries is 100 millimeters of mercury, and the partial pressure of carbon dioxide is 40 millimeters of mercury. The partial pressure of oxygen in the veins is 40 millimeters of mercury, and the partial pressure of carbon dioxide is 46 millimeters of mercury.
      Figure 8.13 The partial pressures of oxygen and carbon dioxide change as blood moves through the body.
  3. Figure 8.20 The kidneys are responsible for removing excess H+ ions from the blood. If the kidneys fail, what would happen to blood pH and to hemoglobin affinity for oxygen?
    The graph plots percent oxygen saturation of hemoglobin as a function of oxygen partial pressure. Oxygen saturation increases in an S shaped curve, from 0 to 100 percent. The curve shifts to the left under conditions of low carbon dioxide, high p H, and low temperature, and to the right in conditions of high carbon dioxide, low p H, or high temperature.
    Figure 8.20 The oxygen dissociation curve demonstrates that, as the partial pressure of oxygen increases, more oxygen binds hemoglobin. However, the affinity of hemoglobin for oxygen may shift to the left or the right depending on environmental conditions.

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