С момента открытия в XVII столетии английским Doctor U. Garvey of the law of blood movement through the vessels by science has established that there is a complex system of conducting elements in the body. These are veins, capillaries and human arteries. They have a unified structure plan, since in the process of embryogenesis they were formed from one germ layer - mesoderm. Due to the difference in the functions performed by a certain type of vessels, they have developed certain structural features. In our article we will focus on the specific properties of the arterial vessels involved in the small and large circles of blood circulation.
How to build an arterial wall
Гибкие, прочные и эластичные трубки, выходящие из hearts are human arteries. According to them, the blood moves to all organs and tissues, bringing oxygen to the cells, as well as nutrients: glucose, amino acids, glycerin and fatty acids. At the same time, it takes away cellular metabolism products and carbon dioxide. In all arterial vessels, the blood moves under pressure and at a sufficiently high speed. To preserve integrity, the walls of the arteries must be very strong. They have a three-layer structure, which we consider in more detail.
Internal structure
Three vessel shells:external, middle and internal, have differences, which is explained by the functions they perform. Thus, the outer layer is represented by loose connective tissue, penetrated by nerve endings. Excitement, passing through them, causes a change in the lumen of the artery, which affects the blood pressure index inside the vessel. The middle layer of the artery consists of cross-striped fibers, and also contains smooth muscle tissue. In addition to them in the arteries there are connective tissue strands containing elastin protein. Due to the contraction and relaxation of the muscle layer, the lumen of the vessels changes. It is regulated by the nerve fibers of the autonomic nervous system. Thus, excitation in the sympathetic section causes a narrowing of the arteries, and in the parasympathetic - the expansion of their diameter. The inner layer of blood vessels mainly consists of a special connective tissue - the endothelium, has a very smooth surface and provides ideal conditions for the flow of blood through it. As can be seen, all layers of the artery wall best perform the function of blood transfer under pressure and at high speed.
Consider the most important arterial vessels in the human body. These include the aorta, pulmonary and coronary vessels.
Aorta
Being the largest artery of our body, the aortaout of the left ventricle and is divided into three branches: the ascending part, the arc and the descending branch. They provide blood to all internal organs and tissues. Its pressure is 120–150 mm Hg. Art. In order to withstand constant strokes from the portions of blood ejected from the heart, the middle layer of the artery consists of powerful muscle tissue that quenches excessive vibrations and promotes blood flow into the systemic circulation. Rhythmic contractions of the aortic wall can be detected by external palpation of the radial artery of the left wrist. Thinning of the muscular layer, loss of elasticity of it leads to the development of aortic aneurysm - a serious pathology that represents a threat to life and at the initial stages does not have clear symptoms. This complicates early diagnosis, and the disease can be identified using a method such as an ultrasound scan of the arteries.
Circulatory system
Bright scarlet color, saturated with oxygen andnutrients, arterial blood moves from the heart through the aorta. From here begins a large circle of blood circulation. Further, due to the division of the aorta into three branches, blood flows to the organs of all physiological systems. There is also a small, so-called pulmonary, circle, starting from the right ventricle. From it leaves the pulmonary artery, which carries venous blood to the alveolar vesicles of the lungs, which was collected by the superior and inferior vena cava from the systemic circulation. It must be remembered that in the right side of the heart is venous blood, a portion of which is released into the pulmonary artery. The pressure in it is also quite high, although lower than in the aorta.
Средний слой артерии состоит из миофибрилл smooth muscle tissue alternating with elastic fibers of protein. The left and right branches of the pulmonary artery venous blood enters the lungs, where gas exchange occurs: carbon dioxide enters the alveolar cavity, and oxygen diffuses into the blood, the molecules of which combine with the respiratory pigment - hemoglobin.
As you can see, the pulmonary artery involved in the pulmonary circulation carries venous blood entering the lungs.
Coronary vessels
The heart is one of the most efficient muscular.organs working rhythmically. It provides the entire body with blood, but also itself needs an uninterrupted supply of trophic substances and oxygen. To carry out its vital activity, the organ has its own system of vessels.
It includes branches of the artery emanating fromthe initial portion of the aorta, called the bulb. The mouths of the coronary vessels are immediately behind the aortic valve leaflets, preventing blood from returning to the left ventricle of the heart. Up to 500 liters of blood passes through the coronary vessels per day, which indicates a large load to which the blood supply system of the heart is subjected. The middle layer of the artery consists of muscle and elastic fibers and, due to the development of atherosclerosis or with frequent sharp spasms, may lose its elasticity. The lumen of the vessel is reduced, which provokes necrosis of the heart muscle - myocardial infarction.
Blood pressure
Earlier we found that blood in the arteriesmoves under pressure and at high speed. Blood pressure is associated with phases of cardiac activity: systole and diastole, and at normal vascular tone is approximately equal to 120/70 mm Hg. Art. It is measured with a pressure gauge on the brachial artery. If the walls of the arteries narrow, their tone increases and the pressure increases. This condition is called hypertension. It leads to the load of the heart muscle, impaired blood supply and can cause a heart attack without proper treatment.
In this article, we studied the structure of the arteries and established the features of their functioning in the human body.
