The detergent-like substance that keeps the alveoli from collapsing between breaths because it reduces the surface tension of the water film in the alveoli is called:
a. Lecithin
b. Bile
c. Surfactant
d. Reluctant

Verified step by step guidance

1. Understand the function described: the substance prevents alveoli from collapsing by reducing surface tension in the water film lining the alveoli.
2. Recall that alveoli are tiny air sacs in the lungs where gas exchange occurs, and they are lined with a thin layer of water which creates surface tension.
3. Recognize that surface tension tends to make alveoli collapse, so the body produces a detergent-like substance to reduce this tension and keep alveoli open.
4. Identify the substance responsible for this function as 'surfactant,' which is a lipoprotein complex produced by specialized cells in the lungs.
5. Match the correct answer choice to this substance, which is option c. Surfactant.

Key Concepts

Alveoli Structure and Function

Alveoli are tiny air sacs in the lungs where gas exchange occurs. Their thin walls and moist surfaces allow oxygen and carbon dioxide to diffuse efficiently between air and blood. Maintaining alveolar stability is crucial to prevent collapse and ensure proper lung function.

Surface Tension in the Alveoli

The inner surface of alveoli is coated with a thin water film, which creates surface tension that tends to collapse the alveoli. Without a mechanism to reduce this tension, the alveoli would collapse after exhalation, impairing breathing and gas exchange.

Pulmonary Surfactant

Pulmonary surfactant is a detergent-like substance produced by specialized lung cells that reduces surface tension in the alveoli. By lowering surface tension, surfactant prevents alveolar collapse between breaths, facilitating easier lung expansion and efficient respiration.