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blood volume and blood pressure notes
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Provides an overview of the circulatory system, blood vessel structure and function, blood flow pathways, blood pressure regulation, and overall function.
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blood vessels and blood pressurereading
20.1 structure and function of blood vessels
arteries transport blood away from the heart to the capillaries
capillaries are microscopic, porous blood vessels for the exchange of substances between blood
and tissues. contain only the tunica intima
veins drain blood from the capillaries back to the heart
20.1a general structure of vessels
tunics
a. tunica intima: deep. made of endothelium and areolar tissue.
smooth surface allows for blood flow, substance release, and regulation of muscle
contraction in the tunica media
b. tunica media: middle layer. smooth muscle cells, elastic fibers
muscle contraction results in vasoconstriction, relaxation results in vasodilation
c. tunica externa: superficial. areolar connective tissue with elastic and collagen fibers
anchors vessels to surrounding structures
vasa vasorum extends through the externa in large blood vessels
arteries and veins that run parallel are companion vessels
arterioles to venules, large veins to elastic arteries
blood vessels and blood pressure reading 1
, ⤵️ arteries ⤴️ veins
narrow lumen wide lumen
thicker wall thin wall
thickest is media thickest is externa
more elastic and collagen less collagen and elastic
no valves most veins have valves
high pressure low pressure
20.1b arteries
progressively branch into smaller vessels
three types
i. elastic arteries (conducting)
largest artery
large proportion of elastic fibers to accomodate blood ejected from ventricle, and then recoil
during diastole
aorta, pulmonary trunk, brachiocephalic, carotid, subclavian, iliac arteries
ii. muscular arteries (distributing)
distribute blood to specific regions
internal elastic lamina between the media and intima
external elastic lamina between the media and externa
can vasoconstrict and dilate easily, but have less stretch due to mainly being smooth muscle
brachial, anterior tibial, coronary, inferior mesenteric arteries, etc
iii. arterioles
smallest arteries
blood vessels and blood pressure reading 2
, fewer than 6 layers of smooth muscle in media
small arterioles only have intima and a single layer of smooth muscle cells
this smooth muscle is always slightly contracted, and called vasomotor tone (which
regulates systemic blood pressure)
regulated by the vasomotor center in medulla oblongata
sympathetic motor tone results in vasoconstriction
20.1c capillaries
smallest blood vessels
connect arterioles to venules
endothelium on a basement membrane
vesicular transport, bulk flow, diffusion
three types:
a. continuous capillary
complete lining of endothelium, complete basement membrane, have intercellular clefts
plasma, some leukocytes
most capillaries, found in skin and muscle, lungs, CNS
use simple diffusion and pinocytosis
b. fenestrated capillary
complete lining of endothelium, complete basement membrane, have intercellular clefts,
contains fenestrations
large amounts of materials that are filtered or absorbed, proteins
mucous membranes and endocrine organs
c. sinusoid capillary
incomplete lining of endothelium, incomplete or even absent basement membrane
formed elements, large plasma proteins, plasma
red bone marrow, liver, spleen, some endocrine organs
blood vessels and blood pressure reading 3
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