Human blood system and blood directly

The environment, similar to blood, arose a very long time, at the time of the appearance of the first multicellular organisms. It is clear that such a medium was not needed for unicellular organisms. But it gave these species an evolutionary push forward - unicellular ones had to wait until food was near, but cells of more complex organisms fed more stably. Even plants have a similar environment. And yet this article will discuss the circulatory system of man.

Various functions that perform a red liquid in our body are various. The circulatory system is also complex. Blood has at least 6 functions.

1. It "feeds" the cells with nutrients.
2. Eliminates them from waste products.
3. Participates in thermoregulation, providing the best conditions.
4. Disorders the body regulators - hormones.
5. Participates in the immune response, if inside the body suddenly come "strangers".
6. Supports the composition of the body's environment constant.

Formal blood elements were discovered only in the 18th century thanks to the invention of the microscope. However, there is another component of the blood - plasma, its liquid part. However, the plasma is still several times more viscous than water, since it contains proteins. And a considerable contribution to the viscosity of blood is made by red blood cells. If we suffer from dehydration, the blood condenses (as happens with copious sweating and diarrhea).

Most of all in the blood of red blood cells, they provide its color. Also contained in it are faithful guards that protect against infections - lymphocytes, and also platelets, which do not allow blood to flow out completely through a small wound. This is not all about blood, but we are interested in the whole circulatory system of man in general, is not it?

It includes, in addition to blood, more heart and blood vessels. Often, along with the circulatory system, the lymphatic system is also considered, because lymph and blood are closely connected. Nevertheless, in this article we consider only the structure of the circulatory system.

The heart is a very complex muscle with the mechanism of autonomic regulation, but this view has been affirmed for a very long time. A healthy heart consists of two atria and two ventricles. The main part of the heart - the myocardium - has its own system of blood supply. Reverse blood flow in the normal heart is impossible because of the special structure of the heart valves. If you push the door that opens on the principle of "on yourself", you will never get into the room behind this door. So the situation with blood, only she "pull the door", unlike you, can not. The human blood system is perfectly arranged.

Through the arteries, the blood leaves the heart, through the veins - comes to him. In the great circle of blood circulation (from the left ventricle to the organs and back to the right atrium), the blood is rich in oxygen in the arteries, bright red. In the veins of this circle, it is dark, full of carbon dioxide. In a small circle (from the right ventricle to the lungs and from them to the left atrium) - on the contrary.

Of all the fluid that the circulatory system contains, 80% is in the veins. Between the arteries and veins is a large number of microscopically small units - the capillaries. On the arteries of a large circle of blood to go easily - more recently, she received an impulse from the heart. But in the veins everything is much more difficult - to get back, often against gravity, the blood is pushed by special valves. And these valves are assisted by ordinary skeletal muscles. So that there were no ugly veins on your legs, you need to regularly engage in any sport in which the legs are involved. Because the muscles in the legs help the blood to rise higher.

As you can see, the circulatory system of a person allows performing all the numerous functions of blood, and therefore the prevention of her diseases should be dealt with from childhood. For a healthy person, it is enough to eat properly and be physically more active than the average.