Which of the choices below explains why the arterioles are known as resistance vessels?
They distribute blood to various parts of the body.
Their prime function is the exchange of nutrients and wastes between the blood and tissue cells.
They contain a large quantity of elastic tissue.
The contraction and relaxation of the smooth muscle in their walls can change their diameter.
The Correct Answer is D
A. They distribute blood to various parts of the body: While arterioles direct blood flow to different tissues, distribution alone does not explain why they are called resistance vessels. Their role in regulating flow is more about controlling pressure and resistance.
B. Their prime function is the exchange of nutrients and wastes between the blood and tissue cells: Nutrient and waste exchange occurs primarily in capillaries, not arterioles. Arterioles function upstream of capillaries, regulating the flow into these exchange vessels rather than performing exchange themselves.
C. They contain a large quantity of elastic tissue: Arterioles have some elastic fibers, but not in large amounts like elastic arteries. Elastic tissue contributes to vessel recoil, but it is not the main reason they are classified as resistance vessels.
D. The contraction and relaxation of the smooth muscle in their walls can change their diameter: Arterioles can constrict or dilate due to smooth muscle activity, which alters resistance to blood flow. This ability to adjust diameter directly controls peripheral resistance and, therefore, systemic blood pressure, making them the primary resistance vessels in the circulation.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. All contain valves to prevent the backflow of blood:Valves are present in veins, not arteries. Arteries rely on high pressure generated by the heart to maintain forward blood flow, so valves are generally unnecessary.
B. All carry blood away from the heart:By definition, arteries transport blood away from the heart, regardless of whether the blood is oxygenated or deoxygenated. Pulmonary arteries, for example, carry deoxygenated blood to the lungs, while systemic arteries carry oxygenated blood to tissues.
C. All carry oxygenated blood to the heart:Arteries do not carry blood to the heart; veins do. Additionally, some arteries (like the pulmonary arteries) carry deoxygenated blood away from the heart, so oxygen content is not a defining feature.
D. Only large arteries are lined with endothelium:All arteries, regardless of size, have an endothelial lining (tunica intima). This layer is essential for maintaining a smooth blood flow and regulating vascular functions.
Correct Answer is B
Explanation
A. Large intestine:While the large intestine contains some lymphoid tissue, Peyer’s patches are not located here. The large intestine has other immune structures but lacks these organized nodules.
B. Small intestine:Peyer’s patches are clusters of lymphoid follicles primarily located in the distal portion of the small intestine, especially the ileum. They monitor intestinal bacteria and pathogens, contributing to gut-associated lymphoid tissue (GALT).
C. Esophagus:The esophagus has minimal lymphoid tissue and does not contain Peyer’s patches. Its mucosa is primarily designed for transport of food rather than immune surveillance.
D. Stomach:The stomach contains scattered lymphoid tissue but does not house organized Peyer’s patches. Its primary role is digestion, with lymphoid tissue present mainly in the mucosa for local immunity.
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