The Circulatory System 0.0 / 5 ? BiologyHealth, illness and diseaseASAQA Created by: abi-huntCreated on: 06-05-18 19:58 arteries arteries carry blood from the heart to the rest of the body their walls are thick and muscular and have elastic tissue to stretch and recoil as the heart beats, which helps maintain a high pressure the inner lining (endothelium) is folded, allowing the artery to stretch - this also helps maintain the high pressure all arteries carry oxygenated blood except for the pulmonary artery which carries deoxygenated blood from the heart to the lungs 1 of 5 arterioles arteries divide into smaller sections called arterioles these form a network throughout the body blood is directed to different areas of demand in the body by muscles inside the arterioles they contract to restrict the blood flow or relax to allow full blood flow 2 of 5 veins veins take blood back to the heart under low pressure they have a wider lumen with very little elastic tissue veins contain valves to stop blood flowing backward blood flow through veins is helped by contraction of the muscles surrounding them all veins carry deoxygenated blood, except for the pulmonary vein which carries oxygenated blood from the lungs to the heart 3 of 5 capillaries arterioles branch into capillaries substances are exchanged between cells and capillaries, so they're adapted for efficient diffusion capillaries are always found very near cells in exchange tissue so there's a short diffusion pathway their walls are only one cell thick there are a large number of capillaries found together to increase the surface area - the networks of capillaries are called capillary beds 4 of 5 tissue fluid tissue fluid is the fluid that surrounds cells in tissues its made from small molecules that leave the blood plama, eg. oxygen, water and nutrients substances move out of the capillaries, into tissue fluid through pressure filtration at the end of the capillary bed, nearest the arteries, the hydrostatic pressure is greater inside the capillaries than in the tissue fluid as molecules leave through the gaps in capillaires, the pressure in the capillaries is reduced 5 of 5
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