What Are The Arteries, Veins and Capillaries

Nowhere in the world there is no transport system whose performance is comparable to the effect of the system of blood circulation in the human body.

Great roads and highways of all kinds linking major cities to them could deliver food and other necessary supplies. Such large pathways in the body are called arteries – vessels that carry blood from the heart. In the opposite direction of are veins, through which the blood returns to the heart.

However, the small towns and villages are also needed food and supplies. Small roads and streets reaching the villages and houses, such as capillaries in the human body reaching to at least the cells.

The arteries lie deep in the tissues, except in the area of the wrist, on the top of the foot, at the temples and on the sides of neck. On any of these places can feel the pulse, which is very important to the doctor.

Major arteries have valves at the place where out of the heart. Heart valves are made of many elastic fibers and muscles that can expand and contract. Arterial blood is bright red and moves through the arteries in the waves.

The veins lie closer to the surface of the skin; blood in them is a darker color, and moves smoother; they have valves at certain distances along the whole of its flow.

Far from the heart in every part of the body, large blood vessels become tiny, thin as hairs, and are called the capillaries. Capillaries is 50 times thinner than the thinnest human hair! It is so thin that the blood cells passing through capillaries only one after the other, which means that the blood passes through the capillaries very slowly.

What happens when blood flows through a capillary? The blood does not leave the capillaries but capillary wall is thin and consists of only one layer of cells. Through the wall the blood handover its oxygen to the surrounding tissues, and in return receive carbon dioxide as it released the tissues around the capillaries. At the same time, from the blood passes other substances which ensure nutrition of tissues, and harmful products entering the capillaries.