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Structural Differences in Blood Vessels, Fenestrated Capillaries:…
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Fenestrated Capillaries: Endothelial Cells joined
by gap junctions and have intercellular clefts.
Oval pores covered by basal lamina material
(connects epithelial cells to connective tissue) Allows passage of fluid and small solutes.
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Sinusoids: Endothelial cells with fewer tight junctions with
large intercellular clefts.
Large irregularly-shaped lumens and large fenestration.
(allows movement of large molecules and blood cells
across the sinusoid wall)
HEART
Arteries: Transport blood away from the heart.
Characterized by amount of smooth
muscle in the tunica media
Elastic Arteries: Largest in diameter/Large Lumens
Thick walls.
Elastin is all three walls.
More elastin, less smooth muscle
(able to recoil as the heart ejects blood into them)
Muscular Arteries: Thickest tunica media. More smooth muscle, less elastic tissue
(vasodilation/vasoconstriction)
Arterioles: smallest artery
wall of tunica intima wrapped by a few smooth muscle fibers
Regulates blood to capillary beds
Capillaries: Only a very thin walls of tunica intima
At strategic intervals, surface is covered with pericytes (smooth muscle-like cells that stabilize the capillary wall and control permeability)
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Continuous Capillaries: Endothelial cells are joined by tight junctions making an uninterrupted lining.
Junctions leave gaps called intercellular clefts (allowing fluid and small solutes to pass through)
Arteriole: Connect muscular arteries to capillary bed.
Regulates blood flow into individual capillary beds.
Terminal Arteriole: Branches into 10 or more true capillaries. Blood Flow through the capillary bed is controlled by this diameter
Vascular Shunt: A direct terminal for oxygenated and nutrient-rich blood to feed into the capillary bed.
Contains Metarteriole and Thoroughfare channel.
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Precapillary Sphincter:
as capillaries branch off of the Metarteriole, each capillary is surround by a cuff of smooth muscle.
(They can open and close, controlling which way blood will flow.)
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When precapillary Sphincters are closed, blood is forced to travel through the Vascular shunt
True Capillaries
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More Fluid always leaves the atrial end of the capillary bed.
Excess interstitial fluid is typically picked up by the lymphatic system.
True Capillaries: As blood passes through, material is constantly moving either into the capillary or out into the interstitial fluid.
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Interstitial Fluid: very little fluid because of the lymphatic vessels causing low interstitial fluid hydrostatic pressure.
As blood from the Arteriole travel trough the capillaries, the Hydrostatic Pressure, also capillary blood pressure, is greater than the Colloid osmotic Pressure, which forces water and small solutes through the capillary wall.
As blood travels to the Venule end,Hydrostatic pressure decreases, causing the Colloid osmotic pressure to be greater. Greater osmotic pressure will cause fluid to be drawn into the cell.
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Vasodilation causes an increase in lumen diameter, which makes blood pressure decrease
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