Question

question 4
1 pts
which structural feature facilitates oxygen diffusion from the alveolar air into the blood in lung capillaries?
the alveolar and capillary walls are both very thin.
the alveolar and capillary surfaces are both extremely large.
the lung capillaries accommodate a large amount of blood at one time.
each red blood cell comes close to alveolar air.
all of these are correct.
question 5
1 pts
an obstructive lung disorder that is characterized by recurring spasms of the smooth muscles in the wall of the bronchial air passages is
chronic obstructive pulmonary disease.
asthma.
emphysema.
dyspnea.
question 6
1 pts
the exact amount of oxygen in blood depends mainly on the amount of
platelets.
white blood cells.
hemoglobin.
protein.

Explanation:

• Question 4:
• Thin alveolar and capillary walls (\(1\) - \(3\) cell layers) minimize diffusion distance.
• Large alveolar and capillary surfaces (\(\sim70m^{2}\) in lungs) increase diffusion area.
• Lung capillaries holding \(\sim70ml\) blood at rest and red blood cells (RBCs) near alveoli (due to thin walls) aid diffusion. All factors enhance \(O_{2}\) transfer.
• Question 5:
• Asthma: Bronchial smooth - muscle spasms (bronchoconstriction), mucus overproduction narrow airways. Chronic obstructive pulmonary disease (COPD) (e.g., emphysema) has airway obstruction (e.g., alveolar damage), but asthma’s key is spasms. Emphysema has alveolar wall destruction. Dyspnea is shortness of breath (symptom, not disorder).
• Question 6:
• Hemoglobin (\(Hb\)) in RBCs binds \(O_{2}\) (\(1.34ml O_{2}/g Hb\)). Platelets (clotting), white blood cells (immune), and proteins (e.g., plasma proteins) don’t carry \(O_{2}\) like \(Hb\).

Answer:

• Question 4: All of these are correct.
• Question 5: asthma.
• Question 6: hemoglobin.