Wednesday, similar to the blood, there was a long time ago, in the time of appearance of the first multicellular organisms.It is understood that single-celled organisms such environment was not required.But she gave these kinds of evolutionary push forward - unicellular had to wait until the next meal would be, but the cells of more complex organisms fed more stably.Even plants have a similar background.Still, this article will discuss the human circulatory system.
various functions that carries red liquid in our body.Complex and circulatory system.Blood carries at least six functions.
- It "feeds" the cells with nutrients.
- deliver them from the wastes.
- Participates in thermoregulation, providing the best conditions.
- spread around the body regulators - hormones.
- involved in immune response, when inside the body suddenly come "alien".
- Supports the body composition of the medium constant.
blood cells were discovered only in the 18th century with the invention of the microscope.But there is another component of blood - plasma, the liquid part of it.However, plasma is still several times more viscous than water, since it contains proteins.And a considerable contribution to the viscosity of the blood make red blood cells.If we suffer from dehydration, the blood thickens (this happens when sweating and diarrhea).
Most red blood cells in the blood, they provide the color.Also contained in it, and a safe guard to protect against infections - lymphocytes, and platelets are more that do not allow blood to flow completely through the small wound.It's not all about the blood, but we are interested in the entire circulatory system of the person as a whole, is not it?
It includes, in addition to the blood vessels and even the heart.Often considered, together with the circulatory and lymphatic system because lymph blood linked very closely.Yet, in this article we consider only the structure of the circulatory system.
heart - it is very difficult to arm arranged with a mechanism independent regulation, but this opinion was approved a long time.Healthy heart consists of two atria and two ventricles.The main part of the heart - the myocardium - has its own blood supply.Reverse blood flow in the normal heart is not possible because of the special structure of the heart valves.If you push the door, which opens on the principle of "on", you will never get into the room behind this door.The same situation is with the blood, but it is "pull the door," unlike you, can not.Human circulatory system is arranged perfectly.
blood out through the arteries of the heart through a vein - comes to him.In the systemic circulation (from the left ventricle to the authorities and back to the right atrium) in the arteries of blood rich in oxygen, bright scarlet.In the veins of this circle it is dark, full of carbon dioxide.In the small circle (from the right ventricle to the lungs, and from them to the left atrium) - on the contrary.
Of all the liquid which contains the circulatory system, 80% comes from a vein.Between arteries and veins are a large number of microscopically small units - capillary.The arteries of the great circle of blood to go easy - she recently received a boost from the heart.But in the veins is much more difficult - to get back, often against gravity, the blood is pushed by special valves.And help these valves ordinary skeletal muscle.So that was not ugly extensions, leg veins, you need to regularly engage in any activities, which involved foot.Because the muscles in your legs to help the blood to rise above.
As you can see, the human circulatory system allows all of the many functions of the blood, and therefore the prevention of diseases it should be dealt with from childhood.For a healthy person is enough to eat right and be physically active medium.
