Question

Which of the following is correct regarding lecithin?

• A. It lowers surface tension in alveoli
• B. It can be produced by pneumocyte-II
• C. It is a phospholipid that prevents the collapsing of alveoli
• D. All of the above

Answer 1

The correct option is D All of the above

The wall of the alveoli has two layers. The inner layer is made up of simple squamous epithelium whereas the outer layer is composed of yellow fibrous connective tissue. The squamous cells are called pneumocytes which are of two types. Pneumocyte-I is involved in the exchange of gases whereas pneumocyte-II secretes lecithin that lines the alveoli normally. Lecithin is a phospholipid that acts as a surfactant. It has both hydrophilic and hydrophobic ends. The hydrophilic ends attach to the water molecules in lungs and the hydrophobic ends face towards the air. So it reduces the force of water on lungs and thereby reduces the surface tension. It keeps the alveoli open and prevents alveoli from collapsing.
Therefore, all the given statements are true with respect to lecithin.