Question

The alveoli are lined by simple squamous epithelium which is coated with a thin film of lecithin, a phospholipid. What purpose does this serve?

• A. Lecithin reduces the friction between the millions of alveoli in the lungs
• B. Lecithin protects against infections
• C. Lecithin increases the surface tension and prevents the alveoli from bursting
• D. Lecithin lowers the surface tension and prevents the alveoli from collapsing

Answer 1

The correct option is D

Lecithin lowers the surface tension and prevents the alveoli from collapsing

When air laden with moisture comes in contact with wall of the alveoli, high surface tension can result in the collapse of the wall. Lecithin coating on the wall acts as a surfactant and reduces the surface tension, reducing the possibility of a collapse.