21) Precapillary sphincters allow blood to leave this structure and enter true capillaries.
A) sinusoids
B) fenestrated capillaries
C) continuous capillaries
D) metarterioles
E) none of the above
22) Collective name for the structures that drain the cranium.
A) vascular anastomosis
B) dural sinuses
C) internal jugular vein
D) cavernous sinuses
E) inferior vena cava
23) Present in most capillaries, these structures are absent in those of the blood-brain barrier.
A) tight junctions
B) endothelial cells
C) basement membrane
D) intercellular clefts
E) pericytes
24) Vessels of the small intestines, renal glomerulus, and synovial membranes that allow passage of fluid and solutes through "windows" in the endothelium.
A) sinusoids
B) fenestrated capillaries
C) continuous capillaries
D) metarterioles
E) none of the above
25) Microvasculature that provides nourishment to the outer walls of the aorta.
A) tunica intima
B) subendothelial layer
C) tunica media
D) tunica externa
E) vasa vasorum
26) Which layer of blood vessels contains smooth muscle tissue?
A) tunica intima
B) tunica media
C) tunica externa
D) tunica adventitia
27) Most small molecules pass through a capillary wall through which route?
A) via direct diffusion through the endothelium
B) via pinocytotic vesicles
C) through intercellular clefts
D) through tight junctions
28) Functionally, there are no valves in arteries (as opposed to in veins) because
A) valves direct blood only toward the heart and arterial blood passes away from the heart.
B) valves would tear apart from the high arterial pressure.
C) arteries get more atherosclerosis, so valves would cause lethal blood clotting.
D) the blood pressure in arteries is high enough that there is no backflow of blood.
29) Blood pressure is highest in the
A) elastic arteries.
B) arterioles.
C) veins.
D) capillaries.
30) The hepatic portal system has two distinct capillary beds separated by a portal vein. What are the functions of these two capillary beds?
A) The first picks up digested nutrients, and the second delivers these nutrients to liver cells.
B) The first nourishes the digestive tube, and the second picks up nutrients from the digestive tube.
C) The first provides oxygen to the liver, and the second picks up nutrients from the liver.
D) The first picks up toxins from the liver, and the second delivers them to the digestive tube for detoxification.