CH. 23 Vessels and Circulation Flashcards
What are the 3 classes of blood vessels? Give a brief explanation of their pathways.
arteries, capillaries, and veins
In systemic circulation, as ventricles of the heart contract, arteries convey blood away from the heart to the body. Arteries branch into smaller and smaller vessels until they feed into capillaries, where gas and nutrient exchange occurs. From the capillaries, veins return blood to the heart.
What is the site where two or more arteries (or two or more veins) converge to supply the same body region?
Anastomosis
What are arteries that provide only one pathway through which blood can reach an organ called?
end arteries
What are the 3 layers that surround artery and vein walls?
tunics surround the lumen, or inside space, of the vessel through which blood flows
1) Tunica intima: innermost layer of a blood vesel; composed of endothelium and a subendothelial layer of areolar CT
2) Tunica media: middle layer of the vessel wall: composed of circularly arranged layers of smooth muscle cells; sympathetic innervation of smooth muscle is what causes vasoconstriction and vasodilation
3) Tunica externa: outermost layer of the blood vessel wall that is composed of areolar CT and elastic and collagen fibers; helps to anchor vessels to other structures
What is the difference in function of arteries in systemic circulation and pulmonary circulation?
Arteries in the systemic circulation transport oxygenated blood to the body tissues while arteries in the pulmonary circuit transport deoxygenated blood to the lungs
What are the 3 basic types of arteries?
1) Elastic arteries: largest arteries that conduct blood away from the heart to the smaller muscular arteries
2) Muscular arteries: medium sized arteries that distribute blood to body organs and tissues; confined to two circumscribed rings - internal elastic lamina (separates the tunica intima from the tunica media) and the external elastic lamina (separates the tunica media from the tunica externa)
3) Arterioles: smallest arteries; arteriole vasoconstriction decreases blood flow into the capillaries, whereas arteriole vasodilation increases blood flow into the capillaries
What is the function and basic structure of capillaries?
smallest blood vessels, that connect arterioles to venules
most capillaries consist solely of a tunica intima composed of a very thin, single layer of endothelium and a basement membrane; there is no subendothal layer
Why is a thin wall and narrow vessel diameter optimal in capillaries?
diffusion of gases and nutrients between blood in the capillaries
and body tissues. Oxygen and nutrients from the blood can
pass through the endothelial lining to the tissues, whereas carbon
dioxide and waste products may be removed from the tissues
and enter the cardiovascular system for removal
Describe the function of a precapillary sphincter.
a smooth muscle ring at the orgin of each true capillary that controls blood flow; sphincter relaxation permist blood flow into the true capillaries whereas sphincter contractiuon causes blood to flow directly from the metarteriole into the postcapillary venule
precapillary sphincters open when the tissue needs nutrients and they close when the tissue’s needs have been met - vasomotion
What are the 3 basic kinds of capillaries?
1) continuous capillaries
2) fenestrated capillaries
3) sinusoids
What is the general function of veins in the cardiovascular system?
drain capillaries and return the blood to the heart; systemic veins transport deoxygenated blood to the right atrium of the heart, whereas pulmonary veins tranpsport oxygenated blood to the left atrium of the heart
What is the distinction between a venule and a vein?
Venules: smallest veins, companions with arterioles because they both supply the same areas and generally of similar sizes
Veins: a venule becomes a vein when its diameter is greater than 100 micrometers
What is the purpose of valves in veins?
to prevent blood from pooling in the limbs and assist blood moving back to the heart; formed primarily of tunica intima and strengthend by elastic and collagen fibers
one way valves that close to prevent backflow
Explain the general arterial flow out of the heart.
Systemic circulation - oxygenated blood is pumped out of the left ventricle of the heart and enters the ascending aorta; left and right coronary arteries emerge immediately from the wall of the ascending aorta and supply the heart; ascending aorta curves toward the left side of the body to become the aortic arch; aortic arch projects inferiorly as the descending thoracic aorta
Explain the general venous return to the heart
once oxygenated blood is distributed throughout the body. it retuns to the heart through veins that often share the same names as their corresponding arteries
left and right brachiocephalic veins
superior vena cava
inferior vena cava
