Blood circulation call the movement of blood on vessels providing a metabolism between body tissues and the external environment. In a human body the blood circulation is carried out on the closed cardiovascular system.
Instruction
1. The person, mammals and birds has a four-chamber heart, the continuous longitudinal partition divides it into the right and left half, each of which is divided into two cameras — an auricle and a ventricle. These two cameras are reported among themselves by the openings equipped with folding valves. Valves are capable to open in one direction therefore they pass blood only from auricles in ventricles.
2. Heart is in a chest cavity, it is surrounded by a soyedinitelnotkanny cover which is called pericardial bag. Two of its thirds are located in the left part of a chest cavity, and one third — in right. Pericardial bag protects heart, mucous secretion which it allocates, reduces friction at reduction.
3. Arteries call vessels on which blood moves from heart to bodies and fabrics, and veins — on which it is delivered to heart. Thin arteries (arteriola) and veins (venula) connect among themselves network of blood capillaries.
4. The lower and upper hollow veins fall into the right auricle, and two pulmonary — in left. Thanks to operation of folding and semi-lunar valves the blood current in heart goes only in one direction — from auricles to ventricles. From ventricles blood comes to a pulmonary trunk and an aorta.
5. The warm cycle is the period during which there is one reduction of heart and its subsequent relaxation. A systole call reduction of a cardiac muscle, and a diastole — its relaxation. The cycle includes three phases: reduction of auricles (0.1 c), reduction of ventricles (0.3 c) and also general relaxation of auricles and ventricles (0.4 c).
6. Rhythmic reductions and relaxations of auricles and ventricles provide the movement of blood in one direction, from ventricles it comes to small (pulmonary) and big (tulovishchny) blood circulation circles.
7. In the left ventricle the big circle of blood circulation begins. Arterial blood comes to an aorta, the largest artery. The aorta branches on smaller arteries which bear blood to bodies. Arteries are divided into smaller vessels — arteriola, they pass into network of capillaries which penetrate all fabrics and deliver them oxygen and also nutrients. Then blue blood gathers in two big vessels — the upper and lower hollow veins, they join the right auricle.
8. In the right ventricle the small circle of blood circulation originates. The ventricle leaves arterial the pulmonary trunk which is divided into arteries which bear blood to lungs. Large arteries branch on smaller arteriola which then pass into network of capillaries. They braid walls of alveoluses where exchange of gases is carried out. Then the arterial blood oxygenated gets to the left auricle. In veins of a small circle of blood circulation arterial blood, and in her arteries — venous flows.
9. At the same time not all volume of blood of an organism circulates, its considerable part is in a spleen, a liver, easy and hypodermic vascular textures which form blood depot. It allows to provide quickly fabrics and bodies with oxygen in emergency situations.