A large circle of blood circulation - a masterpiece of engineering art

Can you imagine a house in which there is a complicated pipeline system filled with a very valuable liquid that continuously transports water, food, oxygen and waste disposal? In addition, the pipes themselves are able to rebuild and build up, adapting to changes in the house. Such an engineering structure would cause admiration for everyone.

But our circulatory system is capable of more. It regulates body temperature, moves a huge number of different hormones that carry important information to all cells, organizes protection against pathogens. This network is completely flexible and soft, so it is able to absorb all the bumps and bend together with the body. Let's take a closer look at this masterpiece .

Structure of the circulatory system of man

In the center of the circulatory system is a hollow organ - a heart that, like a pump, continuously pumps blood through a closed circle consisting of blood vessels.

The whole system is divided into two components:

• Small circle of blood circulation. A system of blood vessels that connects the heart and lungs together. This circle begins in the right ventricle, the end of it lies in the left atrium. Refers only to the lungs.

• Great circle of blood circulation. It originates in the aorta and ends in the right atrium.

The large circle of blood circulation with its blood vessels permeates the entire body.

The heart is divided into two parts by means of a longitudinal septum. Each of these parts is also divided into two halves by means of a horizontal septum, forming a ventricle and auricle.

The blood first enters the most important vessel of our body - into the aorta. Further the aorta is divided into smaller vessels, and the blood passes into the arteries of the great circle of blood circulation. Gradually arteries branch out and pass into arterioles and capillaries. The diameter of the capillaries is very small - about 10 μm. This means that the red blood cells transporting oxygen to the cells pass through the capillaries one at a time. The walls of the capillary vessels are very thin - they consist of only one layer of cells, but this does not prevent the supply of tissues with nutrients found in the liquid part of the blood (plasma). At the same time, carbon dioxide and exchange products are transferred from the tissues to the capillaries, requiring removal from the body.

Capillaries have a small loop-shaped muscle, through which they can regulate the flow of blood through them to meet the needs of nearby tissues. When the blood leaves the capillaries, it enters the microscopic veins - venules. The venules further merge into the veins, the blood continues to pass through the large circle of blood circulation, returning to the heart. In veins, the blood pressure is lower than in the arteries, but the lumen of the venous vessels is larger.

How is the reverse movement ensured?

Thanks simply to the ingenious device:

• Cup-shaped valves that do not allow blood to flow out of the heart under the influence of gravity.

• Work of skeletal muscles that squeeze closely located veins, pushing blood through one-way valves in the direction of the heart.

• Internal pressure in the thoracic and abdominal cavity, changing during breathing and helping the veins to pump blood into the right atrium.

When venous valves for some reason (pregnancy, hereditary genetic predisposition, obesity or long standing) do not work well, then blood accumulates under the valves, and the veins swell. This condition is called varicose veins.

A large circle of circulation provides oxygen and brain cells. Therefore, the blood circulation of the brain is carried out according to the same laws as for all other organs. If the venous outflow from the vessels of the brain is difficult, then there are dizziness and headaches.

Surprisingly, the efficiency of the human circulatory system is so high that even during a rest for one minute about 5 liters of blood passes through the heart, and the marathoner has about 35 liters every minute.

As our Creator really is a great constructor, whose work is a great circle of blood circulation - it causes admiration!