Textbook Question
Blood flow in the capillaries is steady despite the rhythmic pumping of the heart because of the:
a. Elasticity of the large arteries
b. Small diameter of capillaries
c. Thin walls of the veins
d. Venous valves
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19. The Blood Vessels
Capillaries
Multiple Choice
Which of the following is not true of capillaries?
A
Capillaries have thin walls to facilitate gas exchange.
B
Capillaries have a thick muscular layer to regulate blood flow.
C
Capillaries connect arterioles and venules.
D
Capillaries are the site of nutrient and waste exchange between blood and tissues.
Verified step by step guidance1
Understand the structure and function of capillaries: Capillaries are the smallest blood vessels in the body, and their primary function is to facilitate the exchange of gases, nutrients, and waste products between the blood and surrounding tissues.
Analyze the statement about capillary walls: Capillaries have thin walls, typically one cell layer thick, which allows for efficient diffusion of gases and nutrients. This statement is true.
Evaluate the statement about capillaries connecting arterioles and venules: Capillaries serve as a bridge between arterioles (small arteries) and venules (small veins), allowing blood to flow from the arterial to the venous system. This statement is true.
Consider the statement about nutrient and waste exchange: Capillaries are indeed the primary site for the exchange of nutrients and waste products between the blood and tissues, due to their thin walls and extensive network. This statement is true.
Assess the statement about a thick muscular layer: Capillaries do not have a thick muscular layer; instead, they have a single layer of endothelial cells. The presence of a thick muscular layer is characteristic of larger blood vessels like arteries. Therefore, this statement is not true of capillaries.
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