MCAT Biology Practice Test 6: The Respiratory System

1. All of the following facilitate gas exchange in the lungs EXCEPT:

• A. thin alveolar walls.
• B. multiple subdivisions of the respiratory tree.
• C. differences in the partial pressures of O₂ and CO₂.
• D. active transporters in alveolar cells.

2. Which of the following associations correctly pairs a stage of respiration with the muscle actions occurring during that stage?

• A. Inhalation—diaphragm relaxes
• B. Inhalation—internal intercostal muscles contract
• C. Exhalation—diaphragm contracts
• D. Exhalation—external intercostal muscles relax

3. Total lung capacity is equal to the vital capacity plus the:

• A. tidal volume.
• B. expiratory reserve volume.
• C. residual volume.
• D. inspiratory reserve volume.

4. The intrapleural pressure is necessarily lower than the atmospheric pressure during:

• A. inhalation, because the expansion of the chest cavity causes compression of the intrapleural space, decreasing its pressure.
• B. inhalation, because the expansion of the chest cavity causes expansion of the intrapleural space, decreasing its pressure.
• C. exhalation, because the compression of the chest cavity causes compression of the intrapleural space, decreasing its pressure.
• D. exhalation, because the compression of the chest cavity causes expansion of the intrapleural space, decreasing its pressure.

5. A patient presents to the emergency room with a stab wound to the left side of the chest. On a chest x-ray, blood is noted to be collecting in the chest cavity, causing collapse of both lobes of the left lung. The blood is most likely located between:

• A. the parietal pleura and the chest wall.
• B. the parietal pleura and the visceral pleura.
• C. the visceral pleura and the lung.
• D. the alveolar walls and the lung surface.

6. Each of the following statements regarding the anatomy of the respiratory system is true EXCEPT:

• A. the epiglottis covers the glottis during swallowing to ensure that food does not enter the trachea.
• B. the trachea and bronchi are lined by ciliated epithelial cells.
• C. the pharynx contains two vocal cords, which are controlled by skeletal muscle and cartilage.
• D. the nares are lined with vibrissae, which help filter out particulate matter from inhaled air.

7. Which of the following is a correct sequence of passageways through which air travels during inhalation?

• A. Pharynx → trachea → bronchioles → bronchi → alveoli
• B. Pharynx → trachea → larynx → bronchi → alveoli
• C. Larynx → pharynx → trachea → bronchi → alveoli
• D. Pharynx → larynx → trachea → bronchi → alveoli

8. Idiopathic pulmonary fibrosis (IPF) is a disease in which scar tissue forms in the alveolar walls, making the lung tissue significantly more stiff. Which of the following findings would likely be detected through spirometry in a patient with IPF?

Decreased total lung capacity

Decreased inspiratory reserve volume

Increased residual volume

• A. I only
• B. II only
• C. I and II only
• D. I, II, and III

9. Studies have indicated that premature babies are often deficient in lysozyme. What is a possible consequence of this deficiency?

• A. Respiratory distress and alveolar collapse shortly after birth
• B. Increased susceptibility to certain infections
• C. Inability to humidify air as it passes through the nasal cavity
• D. Slowing of the respiratory rate in response to acidemia

10. Some forms of pneumonia cause an excess of fluids such as mucus or pus to build up within an entire lobe of the lung. How will this affect the diffusion of gases within the affected area?

• A. Carbon dioxide can diffuse out, but oxygen will not be able to enter the blood.
• B. Oxygen can diffuse into the blood, but carbon dioxide cannot diffuse out.
• C. No change in diffusion will occur.
• D. No diffusion will occur in the affected area.

11. Some people with anxiety disorders respond to stress by hyperventilating. It is recommended that these people breathe into a paper bag and then rebreathe this air. Why is this treatment appropriate?

• A. Hyperventilation causes an increase in blood carbon dioxide, and breathing the air in the bag helps to readjust blood levels of carbon dioxide.
• B. Hyperventilation causes a decrease in blood carbon dioxide, and breathing the air in the bag helps to readjust blood levels of carbon dioxide.
• C. Hyperventilation causes an increase in blood oxygen, and breathing the air in the bag helps to readjust blood levels of oxygen.
• D. Hyperventilation causes a decrease in blood oxygen, and breathing the air in the bag helps to readjust blood levels of oxygen.

12. A patient presents to the emergency room with an asthma attack. The patient has been hyperventilating for the past hour and has a blood pH of 7.52. The patient is given treatment and does not appear to respond, but a subsequent blood pH reading is 7.41. Why might this normal blood pH NOT be a reassuring sign?

• A. The patient's kidneys may have compensated for the alkalemia.
• B. The normal blood pH reading is likely inaccurate.
• C. The patient may be descending into respiratory failure.
• D. The patient's blood should ideally become acidemic for some time to compensate for the alkalemia.

13. Premature infants with respiratory distress are often placed on ventilators. Often, the ventilators are set to provide positive end-expiratory pressure. Why might this setting be useful for a premature infant?

• A. Premature infants lack surfactant.
• B. Premature infants lack lysozyme.
• C. Premature infants cannot thermoregulate.
• D. Premature infants are unable to control pH.

14. In emphysema, the alveolar walls are destroyed, decreasing the recoil of the lung tissue. Which of the following changes may be seen in a patient with emphysema?

• A. Increased residual volume
• B. Decreased total lung capacity
• C. Increased blood concentration of oxygen
• D. Decreased blood concentration of carbon dioxide

15. Allergic reactions occur due to an overactive immune response to a substance. Which cells within the respiratory tract play the largest role in the generation of allergic reactions?

• A. Alveolar epithelial cells
• B. Macrophages
• C. Mast cells
• D. Ciliated epithelial cells