Blood Vessels pt 1: Exam 2

Identify the two types of capillaries with a complete endothelium.

are continuous capillaries and fenestrated capillaries.

what factors are involved in the formation of varicose veins

are sagging, swollen superficial veins in the thighs and legs. They result from the pooling of blood due to gravity and the failure of venous valves.

Five general blood vessel classes

arteries, arterioles, capillaries, venules, veins

throughfare channel

bypasses capillary bed

sinusoids

capillaries in the liver

Describe a capillary.

is a small blood vessel, located between an arteriole and a venule, whose thin wall permits exchange between blood and interstitial fluid by diffusion.

Continuous capillary

least permeable and most common, permits diffusion of small solutes and lipids

capillary bed

network of capillaries

Valves

permit blood flow in one direction and prevent backflow of blood toward capillaries

How is blood pressure maintained in veins to counter the force of gravity?

valves, the contraction of smooth skeletal muscles squeezes venous blood toward the heart

Total blood volume distribution

venous system: 64% arterial system: 13% heart: 7% pulmonary circulation: 9% systemic capillaries: 7%

Distinguish among efferent vessels, afferent vessels, and exchange vessels.

Efferent vessels (arteries) carry blood away from the heart, afferent vessels (veins) carry blood to the heart, and exchange vessels (capillaries) exchange nutrients, dissolved gases, and wastes between the blood and interstitial fluid.

systemic circuit

transports blood to and from the rest of the body

Why are valves located in veins but not in arteries?

A. In the arterial system, pressures are high enough to keep the blood moving away from the heart and through arteries and capillaries. In the venous system, blood pressure is too low to keep the blood moving back toward the heart. Valves in veins prevent blood from flowing backward whenever the venous pressure drops.

pulmonary circuit

Carries blood to and from gas exchange surfaces of lungs

Venoconstriction

Contraction of smooth muscle fibers in veins, Controlled by the vasomotor center in the medulla oblongata

vasomotion

changes in diameter of the blood vessel brought about by smooth muscle

left atrium

collects blood from pulmonary circuit

right atrium

collects blood from systemic circuit

blood vessels

conduct blood between the heart and peripheral tissues, consisting of the ateries, veins, and capillaries

large vessel walls

contain small arteries and veins for nourishment (vasa vasorum)

At what sites in the body are fenestrated capillaries located?

endocrine glands, the choroid plexus of the brain, absorptive areas of the intestine, and filtration areas of the kidneys.

fenestrated capillaries

have pores in vessel wall; found in kidneys, intestines, and endocrine glands (larger solutes)

precapillary sphincters

regulate blood flow into true capillaries

the venous system

returns blood toward the heart, low pressures

which chamber of the heart receives blood from the systemic circuit?

right atrium