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Multiple Choice
The minute-to-minute blood flow through the capillary beds is determined by the __________.
A
diameter of the arterioles
B
number of red blood cells
C
pressure in the veins
D
rate of lymphatic drainage
Verified step by step guidance
1
Understand the role of capillary beds in the circulatory system: Capillary beds are networks of tiny blood vessels where the exchange of oxygen, nutrients, and waste products occurs between blood and tissues. Blood flow through these beds is regulated to meet the metabolic needs of tissues.
Identify the factors that influence blood flow: Blood flow is primarily determined by the resistance in blood vessels, which is influenced by the diameter of the vessels, particularly the arterioles. Arterioles are small blood vessels that lead into capillary beds and can constrict or dilate to regulate blood flow.
Eliminate incorrect options: The number of red blood cells affects oxygen transport but does not directly regulate minute-to-minute blood flow. Pressure in the veins is relatively low and does not play a significant role in controlling blood flow through capillaries. The rate of lymphatic drainage is unrelated to blood flow regulation.
Focus on the correct factor: The diameter of the arterioles is the key determinant of blood flow through capillary beds. Arterioles can undergo vasoconstriction (narrowing) or vasodilation (widening) in response to signals from the nervous system, hormones, or local tissue conditions.
Conclude the reasoning: Since the diameter of the arterioles directly controls the resistance to blood flow, it is the primary factor determining the minute-to-minute blood flow through capillary beds.