Oxygen saturation of left atrial blood is normally between 96% and 99%. What is the explanation for less than 100% saturation?
a. As blood passes to the alveolar–capillary membrane, a predicted percentage of hemoglobin will not bind with oxygen.
b. During normal respiration, the majority of alveoli are not expanded.
c. Venous blood from the bronchial circulation is returned to the left atrium.
d. A small amount of blood leaks from the right atrium to the left atrium with each ventricular contraction.
C
Venous blood from the bronchial circulation returns directly into the left atrium. The mixing of venous blood decreases the saturation of left atrial blood to a range between 96% and 99%.
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