Structure And Function Of Arteries, Veins And Capillaries

Blood circulates from the heart through the arteries to the capillaries then to the veins and back to the heart There is a decrease in blood pressure as blood moves away from the heart

Blood vessels have a central lumen lined with endothelium. This endothelium lining the central lumen of blood vessels is surrounded by layers of tissue

Arteries have an outer layer of connective tissue containing elastic fibres and a middle layer containing smooth muscle with more elastic fibres The elastic walls of the arteries stretch and recoil to accommodate the surge of blood after each contraction of the heart Blood pressure is higher in arteries compared to veins

To control blood flow, the smooth muscle surrounding arteries can contract causing vasoconstriction or relax causing vasodilation

Capillaries allow exchange of substances with tissues through their thin walls

Veins have an outer layer of connective tissue containing elastic fibres but a much thinner muscular wall than arteries They contain valves to prevent the back flow of blood