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Chapter 21: Blood vessels and circulation
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.
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?
what is it called when the muscles relax and the lumen increases in diameter?
true or false: the CNS can not direct blood supply
branching points of blood vessels
elastic rebound keeps blood flow moving. true or false
true or false: arteries are much smaller than arterioles
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?
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?
The entrance to each capillary is guarded by a _________.
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?
true or false: blood pressure if higher in the arteries than in the veins
is the lumen of veins larger or smaller than that of arteries?
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?
True or false: muscular arteries are the site of pressure points
what causes a pulse?
the precapillary sphincters opening and closing
what determines venous return?
besides muscle activity, what else does venous flow rely on?