structure of arteries, veins and capillaries

An artery is a vessell that carries blood away from the heart. All arteries except for the pulmonary artery and its branches carry oxygenated blood. small arteries are called arterioles. Arteries have elastic tissue in their wall and they have a thick muscle layer in the walls aswell. This structure allows the arteries to cope with the high pressure of blood flow caused by the heart beat. The endothelium is folded allowing the artery to expand.














A vein carries blood towards the heart. All veins except for the pulmonary veins contain deoxygenated blood small veins are called venules. the main veins of the body have valves to prevent blood flowing in the wrong direction. Contraction of body muscles help the blood flow through the veins. Veins are wider than arteries and they have very little elastic or muscle tissue. The space in the centre of the vein is much larger than the arteies.










Capillaries are vessells which transport the blood from arterioles to venules. they are microscopic vessells which are in most of our ogans and tissues in the body. The structure of the capillaeies are very important because it helps with the function of what it does. They are only one cell thick so that they can allow the exchange of oxygen, carbon dioxide, minerals, salts and water to occur between the capillary and the surrounding tissues.