arteries, veins and capillaries

artery function

• carry blood away from the heart, which is always oxygenated apart from the pulmonary artery which goes from the heart to the lungs

artery - structure of the wall

thicker muscular walls

artery - width of lumen

smaller lumen - means decrease in volume, so an increase in pressure

how are arteries adapted to function?

• thicker wall allows blood to be carried under high pressure

• blood is lighter red

vein - function

carry blood to the heart and it’s always deoxygenated apart from the pulmonary vein, which goes from the lungs to the heart

veins - structure of wall

thinner walls

vein - width of lumen

larger lumen

how are veins’ structure adapted to function?

• contain blood under lower pressure as there is a larger volume and walls are thinner

• blood is darker red

• carbon dioxide needs to be quickly removed so more deoxygenated blood can reach the heart to be pumped into the lungs for gaseous exchange

• valves to prevent back flow of blood

capillary - function

• where gaseous exchange occurs - oxygen passes through the capillary wall and into the tissues, while carbon dioxide passes from the tissues into the blood

• where exchange of other substances takes place (useful and waste)

capillary - structure of wall

• very thin wall - one cell thick

• no smooth muscle

• no elastic fibres

capillary - width of lumen

• smallest lumen out of the three (artery and vein)

how are capillaries structure adapted to function?

• thin wall - allows gaseous exchange

• very low pressure to prevent rupture