Question

capillary structure is uniquely adapted for exchange processes, like simple diffusion and osmosis, because __________. a there are many of them b they have valves to control flow c they have only one layer of simple squamous epithelium (endothelium) d they contract

Explanation:

• Option A: While having many capillaries increases the surface area for exchange to some extent, it is not the most crucial factor for simple diffusion and osmosis.
• Option B: Capillaries do not have valves. Valves are mainly found in veins to prevent back - flow.
• Option C: Capillaries have only one layer of simple squamous epithelium (endothelium). This thin wall allows for easy passage of substances by simple diffusion and osmosis. For example, oxygen and carbon dioxide can diffuse across this thin layer between the blood in the capillary and the surrounding tissues.
• Option D: Capillaries do not contract. Arterioles (smaller arteries) have smooth muscle that can contract to regulate blood flow.

Answer:

C. they have only one layer of simple squamous epithelium (endothelium)