Question

The function of surfactant is/are
A)Facilitating lung expansion
B)Maintaining the stable size of the alveoli
C)To reduce the surface tension on the alveoli
D)All of the above

Answer 1

Hint: Pulmonary surfactant is the most important medicine for the basic health system as declared by WHO. It is a surface-active lipoprotein complex produced by the alveolar cells. The artificial surfactants are also available as a supplement.

Complete answer:
To solve this question, we must know about the function of pulmonary surfactants.
The surfactants are lipoproteins in nature. They have both hydrophilic and hydrophobic regions. The hydrophilic head adorns the air water interface whereas the hydrophobic tail faces towards the air. The lipid component reduces the surface tension on the alveoli. (Option C is correct)

Function of Alveoli-
1.It helps in increasing the pulmonary compliance. Compliance means the ability of lungs and the thorax to expand. The surfactant reduces the pressure needed for the lungs to inflate. This reduces the work of breathing. (Option A is correct).
2.The regulation of alveolar size- The surfactant reduces the surface tension more easily when the surfactant is more concentrated. This reduces the size of the alveoli. The increase in surface tension reduces the size of alveoli more effectively. (Option B is correct)
3.Surfactant reduces the fluid accumulation and helps in keeping the air pathway dry by reducing the surface tension.

Hence, the correct answer is option (D)

Note: The proteins present in the surfactants provide innate immunity. They bind to the surface of the pathogens and facilitate WBC for their destruction. It also regulates inflammatory responses. If the surfactant becomes inactive then the lungs become susceptible to inflammation and infection.