An environment similar to blood arose a long time ago, during the appearance of the first multicellular organisms. It is clear that unicellular organisms did not need such an environment. But she gave these species an evolutionary push forward - they had to wait for unicellular animals to be near, but the cells of more complex organisms ate more stably. Even plants have a similar environment. Nevertheless, this article will discuss the human circulatory system.
The functions that a red liquid performs in our body are varied. The circulatory system is also complex. Blood performs at least 6 functions.
- She โfeedsโ cells with nutrients.
- It relieves them of waste products.
- Participates in thermoregulation, providing the best conditions.
- Carries regulators - hormones throughout the body.
- Participates in the immune response if "strangers" suddenly come into the body.
- Maintains a constant composition of the body environment.
Blood cells were discovered only in the 18th century thanks to the invention of the microscope. However, there is another component of blood - plasma, its liquid part. However, plasma is still several times more viscous than water, since it contains proteins. Red blood cells also contribute a lot to blood viscosity . If we suffer from dehydration, then the blood thickens (this happens with profuse sweating and diarrhea).
Most of all in the blood of red blood cells, they provide its color. It also contains loyal guards that protect against infections - lymphocytes, as well as platelets that do not allow blood to flow completely through a small wound. This is not all about blood, but we are interested in the whole circulatory system of a person as a whole, is not it?
It includes, in addition to blood, the heart and blood vessels. Often, along with the circulatory system, the lymphatic system is also considered, because lymph is very closely associated with lymph. Nevertheless, in this article we consider only the structure of the circulatory system.
The heart is a very complex muscle with an autonomous regulation mechanism, 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 blood supply system. Reverse blood flow in a normal heart is not possible due to 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. The situation is the same with blood, only it cannot โpull the doorโ, unlike you,. The human circulatory system is perfectly arranged.
Through arteries, blood leaves the heart, through veins - comes to him. In a large circle of blood circulation (from the left ventricle to the organs and back to the right atrium) in the arteries, the blood is rich in oxygen, 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) - vice versa.
Of all the fluid that the circulatory system contains, 80% are veins. Between arteries and veins there is a large number of microscopically small units - capillaries. Itโs easy to go through the arteries of a large circle of blood - just recently she received an impulse from her heart. But in the veins, everything is much more complicated - to get back, often against gravity, the blood is pushed by special valves. Ordinary skeletal muscles help these valves. Therefore, so that there are no ugly extensions of the veins on the legs, you need to regularly engage in any sport in which the legs are involved. Because the muscles in the legs help the blood rise higher.
As you can see, the human circulatory system allows you to carry out all the many functions of the blood, and therefore the prevention of its diseases should be dealt with from childhood. For a healthy person, it is enough to eat properly and be physically active than the average.