Question

Type I alveolar cells are _______ and ________, which allows for efficient gas exchange. It covers ____ of alveolar surface area.

a) Squamous, thin, 90%
b) Cuboidal, thick, 75%
c) Columnar, flexible, 50%
d) Ciliated, rigid, 25%

Answer 1

Type I alveolar cells are squamous and thin, covering about 97% of the alveolar surface area, which facilitates efficient gas exchange. The correct option is A.

Step-by-step explanation:

Type I alveolar cells are squamous, thin, which allows for efficient gas exchange. These cells comprise a significant portion of the alveolar surface area, and due to their thinness, approximately 25 nm, they are highly permeable to gases. Specifically, type I alveolar cells cover approximately 97% of the alveolar surface area.

In contrast, type II alveolar cells, which are cuboidal and secrete pulmonary surfactant, are interspersed among type I cells. Together, the alveolar cells and the capillaries form a respiratory membrane that facilitates simple diffusion of O₂ and CO₂ between the alveoli and the blood.