Final answer:
Type I alveolar cells are thin, flat cells that cover 97% of the alveolar surface area and are highly permeable to gases, allowing efficient gas exchange. With a large surface area and a thickness of only about 25 nm, they enable optimal oxygen and CO₂ diffusion with the blood.
Step-by-step explanation:
Type I alveolar cells are squamous epithelial cells and highly permeable to gases which allows for efficient gas exchange. It covers 97% of alveolar surface area. Because of their tiny (about 25 nm thick) shape, which provides little to no barrier to the exchange of carbon dioxide and oxygen between the blood in the capillaries and the alveoli, these cells are essential to the respiration process. The amount of gas that can permeate into and out of the lungs is maximized by the enormous surface area of the alveoli, which is roughly 75 m² in the human lung, and the thin nature of the type I alveolar cells.