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27 Cards in this Set
- Front
- Back
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function of arteries |
carry blood away from heart and into arterioles |
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function of arterioles |
smaller arteries that control blood flow from arteries to capillaries |
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function of capillaries |
tiny vessels that link arterioles to veins |
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function of veins |
carry blood from capillaries back to heart |
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structure of arteries, arterioles and veins from outside inwards |
tough outer layer muscle layer elastic layer thin inner lining (endothelium) lumen |
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why is thin inner lining (endothelium) smooth and thin? |
reduces friction and allow fast diffusion |
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Why do arteries have an elastic layer? |
elastic layer stretches and recoils as the heart beats; maintains high pressure and smooths pressure surges |
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Why do arteries' endothelium folded? |
allows artery to stretch allows artery to maintain high pressure |
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Why do arteries have a thick wall overall? |
resists artery bursting under pressure |
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Why do arterioles have a thicker muscle layer than arteries? |
allows lumen of arteriole to constrict, restricting blood flow and controlling its movement into capillaries |
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Why do arterioles have an elastic layer thinner than in arteries? |
blood flow is lower is arterioles |
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Why do veins contain valves? |
To stop blood flowing backwards |
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Why do veins have an overall small wall thickness? |
Low pressure in veins to create any risk of bursting |
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Why do veins have a very thin elastic layer? |
Pressure too small to create a recoil action |
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Why are capillaries always found near cells in exchange tissues? |
so there's a short diffusion pathway |
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Why are capillary walls only 1 cell thick? |
so there's a short diffusion pathway |
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Why is there a large number of capillaries? |
to increase surface area for exchange |
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Why to capillaries have a thin lumen? |
so red blood cells are squeezed flat against side of capillary reduces diffusion distance |
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Why do capillaries have a narrow diameter? |
they spread throughout tissues so no cell ever far from capillary to short diffusion pathway |
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What is tissue fluid? |
Watery liquid that supplies tissues with glucose, oxygen, amino acids, ions in solution and fatty acids The means by which materials are exchanged between blood and cells |
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Step 1 of tissue fluid formation |
high pressure at artery end of capillary |
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Step 2 |
overall outward pressure forces tissue fluid out of blood plasma |
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Step 3 |
as fluid leaves capillary bed, hydrostatic pressure and venule end lowers |
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Step 4 |
tissue fluid forced back into capillaries from hydrostatic pressure outside them |
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Step 5 |
blood plasma has lost water and still contains proteins, so has a lower water potential than tissue fluid water leaves tissue by osmosis, down water potential gradient |
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Purpose of the lymphatic system is to... |
...transfer excess tissue fluid from tissue and back into circulatory system |
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Contents of lymphatic system are moved by |
hydrostatic pressure of tissue fluid that has left capillaries contraction of body muscles that squeeze the lymph vessels |
