If the inner lining of the air sacs is neither thin nor highly vascularized, then what can be inferred about the air sacs?
A) They must not belong to the respiratory system.
B) They cannot be derived from endoderm.
C) They are not efficient sites of gas exchange between air and blood.
D) They must obtain nutrition from some source other than the bloodstream.
E) They cannot effectively moisturize the air before it reaches the lungs.

Question

Quizplus · Accepted Answer

The inner lining of the air sacs, called the alveoli, is where gas exchange between air and blood occurs. If the lining is neither thin nor highly vascularized, it means that the diffusion of gases between air and blood is likely to be difficult and inefficient, indicating that the air sacs are not efficient sites of gas exchange between air and blood.

If the Inner Lining of the Air Sacs Is Neither