For each question, choose the one best answer.
1. Which of the following statements about the blood-gas barrier of the human lung is FALSE?
A. Much of the blood-gas barrier has a thickness of less than 0.3 ^.m.
B. The total area of the blood-gas barrier exceeds 50 square meters.
C. Most of the area of the alveolar wall is occupied by capillaries.
D. If the pressure in the capillaries rises to unphysiologically high levels, the blood-gas barrier can be damaged.
E. Oxygen crosses the blood-gas barrier by active transport.
2. When oxygen moves through the thin side of the blood-gas barrier from the alveolar gas to the hemoglobin of the red blood cell it traverses the following layers in order:
A, Epithelial cell, surfactant, ¡nterstitium, endothelial ceil, plasma, red cell membrane.
B. Surfactant, epithelial cell, interstitium, endothelial cell, plasma, red cell membrane.
C. Surfactant, endothelial cell, interstitium, epithelial cell, plasma, red cell membrane.
D. Epithelium, interstitium, endothelial cell, plasma, red cell membrane.
E. Surfactant, epithelial cell, interstitium, endothelial ceil, red cell membrane.
3. What is the P02 (in mm Hg) of moist inspired gas of a climber on the summit of Mt. Everest (assume barometric pressure is 247 mm Hgl?
4. Which of the following statements about the airways of the human lung is FALSE?
A. The volume of the conducting zone is about 150 ml.
B. The volume of the rest of the lung during resting conditions is about 2.5-3.0 liters.
C. A respiratory bronchiole can be distinguished from a terminal bronchiole because the former has alveoli in its walls.
D. On the average there are about 3 branchings of the conducting airways before the first alveoli appear in their walls,
E. In the respiratory bronchioles the predominant mode of gas flow is diffusion rather than convection.
5. Which of the following statements about the blood vessels of the human lung is FALSE?
A. The pulmonary arteries form a branching pattern which matches that of the airways.
B. The average diameter of the capillaries is about 50 |u,m.
C. Most of the surface of the alveoli is covered with capillaries. D On the average blood spends about 3/4 sec in the capillaries.
E. The mean pressure in the pulmonary artery is only about 15 mm Hg at rest.
6. Which of the following statements about the removal of inhaled dust in the lung is FALSE?
A. Very small particles are filtered out by the nose. B- Particles that deposit on the airways are removed by the mucus escalator.
C. The escalator is propelled by millions of tiny cilia.
D. The mucus comes from mucous glands and goblet cells in the bronchial walls.
E. Particles that reach the alveoli are engulfed by macrophages.
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