BLOOD VESSELS

| General| Arteries| Veins| Capillaries| Main Blood Vessels |

General.

Mammals have a closed blood vascular system. It has this name because blood is transported from the heart to all different parts of the body and back in a set of closed tubes. We have already made a study of the heart as part of the blood vascular system. We are now going to make a stydy of the blood vessels.

Blood vessels differ in structure and function. Blood leaves the heart through the arteries, which conduct the oxygenated blood (except in the case of the pulmonary artery) to the various tissues and organs. Deoxygenated blood returns from the tissues and organs to the heart via a set of vessels, called veins (except the pulmonary vein). The actual exchange of oxygen, carbon dioxide, foodstuffs and waste matter between the blood and the tissue fluid occurs in microscopically small vessels, called capillaries.

We shall now look at the structure and function of arteries, veins and capillaries as well as some of the main blood vessels.

Blood Vessels of the body.

Arteries.

Arteries are vessels which transports blood away from the heart. They branch repeatedly to form arterioles (small arteries), the smallest and thinnest branches of arteries.

The arteries carry blood from the heart
to all organs.

Veins.

Veins are vessels which transports blood to the heart. From the capillaries the blood drains into very small veins called venules, which unite into larger veins along which the blood returns to the heart.

Veins transport blood to the heart

Capillaries.

Arteries and veins are connected by blood capillaries, microscopically small tubes which form a network, the capillary bed in different tissues. The blood capillaries are so small that red blood corpuscles can only move in a single file through it. The exchange of all substances takes place in these capillaries.

Capillaries are important for gaseous exchange.

The Main Blood Vessels.

The main blood vessels are the following: