i. Arteries
carry away blood from the heart
carry oxygenated blood except pulmonary artery which takes blood from the heart to lungs for oxygen
have thick, muscular walls
are elastic
have narrow lumen
all these adaptations are required to withstand high pressure caused by heartbeat
ii. Capillaries
link arterioles and venules to arteries and veins
small in diameter to increase pressure resistance for materials to filter out
thin walled as they consist of a single layer of cells to allow diffusion of substances e.g leucocytes to tissues
thin walled to allow presence of intercellular spaces
large number i.e. numerous to provide a large surface area for exchange of materials
have sphincter muscles at the junction of the arterioles and capillaries to control movement of blood into them
lie close to the body for easy exchange of materials
iii. Veins
carry blood back to the heart
all carry deoxygenated blood except pulmonary vein that carries blood from the heart to lungs
have thinner Walls than arteries
have valves to prevent back flow of blood
have wide lumen
Mohaissack answered the question on October 4, 2017 at 14:26
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