Chapter 21: Blood vessels and circulation

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describe the pathway of the blood

heart to arteries to arterioles to capillaries to venules to veins to heart

the __________ touches the blood and is the most inner lining of the endothelium.

tunica intima

what is the middle layer of the blood vessels?

tunica media; is made up of smooth muscle cells

outer most layer of the blood vessels

tunica externa; lots of collagen

what are the two characteristics of arteries?

they are elastic and contractile

what are the characteristics of the tunica intima?

rippled in arteries

name the characteristics of the tunica media

dominated by smooth muscle and dominated by elastic fibers

name the characteristics of the tunica externa

composed of collagen and elastic fibers

true or false: the contractility arteries is under the control of the parasympathetic nervous system

false; sympathetic nervous system

what is the constriction of the artery?

vasoconstriction

what is it called when the muscles relax and the lumen increases in diameter?

vasodilation

true or false: the CNS can not direct blood supply

false

branching points of blood vessels

anastomoses

elastic rebound keeps blood flow moving. true or false

true

true or false: arteries are much smaller than arterioles

false

where are fenestrated capillaries?

endocrine organs, in kidneys, absorptive areas of the GI tracts

list the characteristics of the fenestrated capillaries

have pores that penetrate endothelial lining and permit water and large solutes as large as small peptides

which of the two types of capillaries are held together by tight junctions?

continuous capillaries

where are continuous capillaries located?

located in all tissues except epithelia and cartilage

list the characteristics of continuous capillaries

permit diffusion of water, small solutes, and lipid-soluble materials; prevent loss of blood cells and plasma proteins

sinusoidal capillaries allow movement of what molecules?

free exchange of large plasma proteins

where are sinusoidal capillaries found?

liver, spleen, bone marrow, and endocrine organs

what is the main function of sinusoidal capillaries?

allows plasma proteins produced by liver to enter the bloodstream

where are capillaries found?

capillary beds

The entrance to each capillary is guarded by a _________.

precapillary sphincter

what is the function of a precapillary sphincter?

to constrict to limit or block blood flow

true or false: your body has more than enough blood to maintain blood flow through all capillaries at all times

false, it only has enough blood for about 25% of it

what controls when precapillary sphincters constrict or relax?

the local environment, specifically a drop in oxygen levels

where is hydrostatic pressure highest?

the vessels

true or false: blood pressure if higher in the arteries than in the veins

true

is the lumen of veins larger or smaller than that of arteries?

larger

how does blood flow up in the veins?

through the use of unidirectional valves

which type of artery tends to have diameters of up to 1 inch?

elastic arteries

True or false: muscular arteries are the site of pressure points

true

what causes a pulse?

the precapillary sphincters opening and closing

what determines venous return?

venous pressure

besides muscle activity, what else does venous flow rely on?

respiratory movements

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