Multiple Choice
Which of the following correctly describes the flow of blood through a mesenteric capillary bed when the precapillary sphincters are constricted?
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19. The Blood Vessels
Capillaries
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How thick are the walls of the alveoli and the capillaries involved in capillary exchange?
A
Four cell layers thick
B
Two cell layers thick
C
One cell layer thick
D
Three cell layers thick
Verified step by step guidance1
Understand the structure of alveoli and capillaries: Alveoli are tiny air sacs in the lungs where gas exchange occurs, and capillaries are small blood vessels that facilitate the exchange of gases, nutrients, and waste products between blood and tissues.
Recognize the importance of thin walls: The walls of alveoli and capillaries need to be thin to allow efficient diffusion of gases such as oxygen and carbon dioxide. Thinner walls reduce the distance over which these gases must travel, enhancing the rate of exchange.
Identify the composition of the walls: The walls of both alveoli and capillaries are composed of a single layer of epithelial cells. In alveoli, this layer is known as the alveolar epithelium, while in capillaries, it is referred to as the endothelial layer.
Consider the physiological advantage: Having walls that are one cell layer thick minimizes the barrier for gas exchange, allowing oxygen to move from the alveoli into the blood and carbon dioxide to move from the blood into the alveoli efficiently.
Conclude with the correct answer: Based on the structure and function of alveoli and capillaries, the correct answer is that their walls are one cell layer thick, facilitating optimal gas exchange.
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