Lungs and capillaries both have porous linings that allow certain substances to move into or out of the structures. Which function do these porous linings most likely serve in living organisms?
A. heat release
B. gas exchange
C. carbohydrate absorption
D. osmotic pressure regulation
The Correct Answer and Explanation is :
The correct answer is B. gas exchange.
Lungs and capillaries play a crucial role in the process of gas exchange, which is vital for maintaining life. The porous linings of these structures allow oxygen and carbon dioxide to pass between the blood and the environment or tissues, facilitating this essential exchange.
Lungs and Gas Exchange
The primary function of the lungs is to bring oxygen into the body and expel carbon dioxide. The lungs contain tiny air sacs called alveoli, which are surrounded by a dense network of capillaries. Both alveoli and capillaries have thin, porous linings made of simple squamous epithelial cells, designed to allow gases to easily diffuse across them.
When you inhale, oxygen enters the alveoli. Due to the concentration gradient, oxygen diffuses from the alveoli into the capillaries, where it binds to hemoglobin in red blood cells and is transported throughout the body. Conversely, carbon dioxide, a waste product of cellular respiration, diffuses from the blood into the alveoli and is exhaled from the body. This gas exchange process happens because the porous linings allow these small gas molecules to move freely between the air in the lungs and the blood.
Capillaries and Gas Exchange in Tissues
Capillaries are the smallest blood vessels, and their porous walls allow the diffusion of gases, nutrients, and waste products between the blood and tissues. Oxygen-rich blood from the lungs travels to body tissues via the circulatory system. Once in the capillaries, oxygen diffuses into the tissues, while carbon dioxide, produced by cells during metabolism, diffuses into the capillaries to be carried back to the lungs for removal.
The porous nature of both lung alveoli and capillaries ensures that gas exchange is efficient and continuous, supporting respiration, the body’s way of obtaining energy. Therefore, the primary function of these porous linings is gas exchange.