Flashcards in Chapter 22- Blood vessels and Circulation Deck (25)
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1
blood vessels
-closed circuit of tubes
-arteries carry blood away from the heart
-capillaries are exchange vessels
-veins return blood to heart
-oxygen does not distinguish arteries from veins
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summary of circulation
heart-arteries-arterioles-capillaries-venules-veins-heart
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blood vessel tissues
endothelium
-smooth surface for blood flow
-simple squamous epithelium
CT
-provides elasticity to withstand BP changes
smooth muscle
-vasoconstriction
-vasodilation
4
blood vessel histology: layers
tunica intima
-innermost
-endothelium on top of CT membrane
-internal elastic membrane
-functions:
--separates blood flow from vessel wall
--prevents blood clotting
--helps regulate BP
5
layers
tunica media
-middle
-bulk of wall
-smooth muscle and elastic CT
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layers
Adventitia (tunica externa)
-arteries: thin
-veins: not so thin
-outer
-made of CT, elastic and collagenous fibers
-attaches artery to surrounding tissues
-contains vasa vasorum
--BV of BV because they are so thick
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arteries: characteristics
strong and elastic
-subdivided into arterioles
8
differences in arteries and veins
-artery wall thicker
-artery lumen appears smaller
endothelium of artery can not contract
9
types of arteries
elastic
-large diameter
-in areas of high pressure
-media:
--high % elastic tissue,
--less smooth muscle
-examples:
--pulmonary trunk, aorta, carotid, subclavian, common iliacs
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types of arteries
muscular
-large to small diameter
-carry blood to skeletal muscles and organs
-media:
--much smoother muscle
--less elastic tissue
-examples
--femoral, carotids, brachials, mesenteric
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arterioles
microscopic continuations of arteries-cant see them
-small diameter
-adventitia is thin
-no external elastic membrane
-no vasa vasorum
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capillaries
consist of
-only intima:
--basement membrane
--simple squamous epithelium
-very thin
-variable permeability
materials exchanged:
-nutrients
-dissolved gases
-wastes
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capillary permeability
maximized by:
-thin wall
-low BP
-slow blood flow
mechanism of permeability:
-diffusion across endothelial cells: lipids, gases
-diffusion through gaps between endothelium: water, small solutes
-diffusion through pores: water, larger solutes
-vesicular transport with pinocytes (ATP involved): large, bound solutes
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continuous capillaries
many:
-tight junctions
-desmosomes
-pinocytes
allow movement by:
-passive diffusion
-active transport
locations:
-CNS
-skeletal muscle
-lungs
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fenestrated capillaries
-swiss cheese appearance
--pores
-allow movement of:
--peptides
--small proteins
--molecules that cant make it through likes wastes, plasma components that arent cells
-locations
--kidneys
--intestines
--intestines
--endocrine glands
--choroid plexus
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sinusoid capillaries
specialized for max exchange by
-large intercellular gaps
-pores
-discontinuous basement membrane
--allows CELLS to enter/exit
-location
--spleen and bone marrow
--liver and adrenal glands
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capillary beds
network of interconnected capillaries
-connection for veins and arteries
-depreived from arterioles
-precapillary sphincters
--manages blood flow to bed
-metarterioles
--a direct connection through the bed
--leads to a throughfare channel
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anastomses
messing with blood flow in capillaries
-collateral arteries
--two arteries fuse
--twice as much blood supplies the arteries
--found in areas with high O2 demand
--allow for variable degree of blood flow to capillary beds. can contract one tube or open both
-arteriovenous anastomosis
--direct connectoin between arteriole and venule
--where blood flow may be hindered by posture
--allows to reroute blood flow if hindered in capillary bed
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venules
smallest veins that collect blood from capillaries
-can lack a media
-scatter, minimal amount of smooth muscles occasionally
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medium sized veins
2-9mm in diameter
-thin media
-few smooth muscle fibers
-thick adventitia
-low bp
-valves
-shape does not need to change, not enough pressure for lots of things that arteries do
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large sized veins
-great veins: superior/inferior vena cava, and tributaries
-thin media
-thcik adventitia
-low BP
-valves
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venous valves
flap like structures projecting inward
-folds of media
-found in extremities
veins have low BP
-valves prevent back flow of blood
movement of blood through veins
-movement of limbs and contraction of muscles
--skeletal muscle pump
--positive pressure to push blood up
-expansion of the thoracic cavity
--involves negative pressure, creating empty space to be filled, sucks blood up
--thoracoabdominal pump
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blood distribution
-unveven
--oxygenated blood in the heart, arteries, and capillaries-1/3 of blood
--deoxygenated, venous blood-2/3 of blood
-known as the blood reservoir
--allows ability to lose fair amount of blood but still be able to survive and escape, essentially extra blood
-veins contract during blood loss
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circuits: pulmonary
pulmonary circuit
-deoxygenated blood goes to lungs from right ventricle
-oxygenated in alveolar capillaries of lungs
-brought to left atrium, then left ventricle
-veins=oxygenated
-arteries=deoxygenated
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