Which blood vessels lack elastic tissue?
muscular arteries and arterioles
venules and veins
capillaries and venules
arterioles and capillaries
The Correct Answer is C
A. Muscular arteries and arterioles: Both muscular arteries and arterioles contain smooth muscle and some elastic tissue within their walls. These elastic components help them withstand pressure changes and regulate blood flow. Because they possess measurable elasticity, they cannot be categorized as vessels lacking elastic tissue.
B. Venules and veins: Veins and venules do contain small amounts of elastic fibers, even though they are far less elastic than arteries. These fibers help accommodate changes in blood volume and allow the vessel walls to stretch as they act as capacitance vessels. Since elastic tissue is present, they do not fit the criterion of lacking elasticity.
C. Capillaries and venules: Capillaries lack elastic tissue entirely because their walls consist of only a single layer of endothelial cells to allow rapid exchange of gases and nutrients. Venules, especially the smallest ones, also have minimal to no elastic tissue, consisting mainly of endothelium and a thin connective layer. This combination makes them the best match for vessels lacking elastic fibers.
D. Arterioles and capillaries: Arterioles possess smooth muscle and contain elastic tissue that allows them to regulate resistance and control blood flow into capillary beds. Capillaries alone lack elastic tissue, but arterioles do not.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. 120/80:This reading falls within the normal blood pressure range. Systolic pressure is at the upper end of normal, and diastolic pressure is well within normal limits, so it does not indicate hypertension.
B. 110/60:This is considered a low-normal blood pressure reading. Both systolic and diastolic pressures are below the thresholds for hypertension, indicating normal or slightly low blood pressure.
C. 170/96:This reading is significantly elevated, with both systolic and diastolic pressures above normal limits. A systolic pressure ≥140 mmHg or a diastolic pressure ≥90 mmHg meets the criteria for hypertension, making this reading indicative of the condition.
D. 140/90:While this reading meets the minimum threshold for stage 2 hypertension, it is less severe than 170/96. It does indicate hypertension but is less markedly elevated compared with option C.
Correct Answer is B
Explanation
A. A decrease in oxygen levels:While low oxygen levels stimulate chemoreceptors, baroreceptors are not primarily sensitive to oxygen. Their function is focused on detecting pressure changes rather than gas concentrations.
B. Changes in arterial pressure:Baroreceptors in the carotid sinus and aortic arch detect stretch in the arterial walls caused by increases or decreases in blood pressure. This information is sent to the cardiovascular center to regulate heart rate and vessel tone, making them pressure-sensitive sensors.
C. An increase in oxygen levels:High oxygen levels do not directly affect baroreceptor activity. Baroreceptors respond to mechanical stretch, not oxygen concentration, so oxygen changes are irrelevant to their primary function.
D. A decrease in carbon dioxide:Carbon dioxide levels primarily influence chemoreceptors, not baroreceptors. While CO₂ can indirectly affect cardiovascular responses, baroreceptors themselves do not respond to changes in CO₂.
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