19. Cardiovascular System: Blood Vessels

The vessel layer that has a direct role in vasoconstriction is the __________.

The endothelium is composed of __________.

Which of the following is the correct sequence of layers in the vessel wall from superficial to deep?

Reduction in the lumen diameter of a blood vessel as the smooth muscle contracts is known as __________.

Which of the layers of an artery wall is regulated by the sympathetic nervous system and many hormones?

Which of the following would not result in the dilation of the terminal arterioles and upstream arterioles in systemic capillary beds? a. a decrease in local tissue O₂ content, b. an increase in local tissue CO₂, c. a local increase in histamine, d. a local increase in pH.

The structure of a capillary wall differs from that of a vein or an artery because a. it has two tunics instead of three, b. there is less smooth muscle, c. it has a single tunic—only the tunica intima, d. none of these.

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.

Multiple Choice More than one choice may apply. Which layer of the artery wall thickens most in atherosclerosis? a. Tunica media b. Tunica intima c. Tunica adventitia d. Tunica externa

Describe neural and chemical (both systemic and local) effects exerted on the blood vessels when you are fleeing from a mugger. (Be careful, this is more involved than it appears at first glance.)

When we are cold or the external temperature is low, most venous blood returning from the distal part of the arm travels in the deep veins where it picks up heat (by countercurrent exchange) from the nearby brachial artery en route. However, when we are hot, and especially during exercise, venous return from the distal arm travels in the superficial veins and those veins tend to bulge superficially in a person who is working out. Explain why venous return takes a different route in the second situation.