The human circulatory system , in addition to the heart, consists of vessels that are different in size, diameter, structure and function. What is the difference between arteries, veins and capillaries? What structural features make it possible to carry out the most important functions? You will find the answer to these and other questions in our article.
Circulatory system
The fulfillment of blood functions is possible due to its movement through the system of blood vessels. It is provided with rhythmic contractions of the heart, which works like a pump. Moving through the blood vessels, blood transports nutrients, oxygen and carbon dioxide, protects the body from pathogens, and provides homeostasis of the internal environment.
The vessels include arteries, capillaries and veins. They determine the path of blood in the body. What is the difference between arteries and veins? Location in the body, structure and functions. Let's consider them in more detail.
How arteries differ from veins: features of functioning
Arteries are vessels that supply blood from the heart to tissues and organs. The largest artery in the body is called the term "aorta." She directly leaves the heart. In arteries, blood moves under high pressure. To withstand it, you need an appropriate wall structure. They consist of three layers. The inner and outer are formed by connective tissue, and the middle - from muscle fibers. Due to this structure, these vessels are capable of stretching, which means they can withstand high blood pressure.
How is the structure of veins different from the structure of arteries? First of all, vessels of a different type carry blood from organs and tissues to the heart. After passing through all cells and organs, it is saturated with carbon dioxide, which carries to the lungs.
Another important issue is what distinguishes the structure of the artery wall and vein. The latter have a thinner muscle layer, therefore less elastic. Since blood enters the veins under slight pressure, their ability to stretch is not so important.
The value of blood pressure in vessels of different types is demonstrated by different types of bleeding. In arterial blood, a pulsating fountain is released with force. It is scarlet, as it is saturated with oxygen. But with venous - it follows a slow stream and has a dark color. It is determined by a large amount of carbon dioxide.
The lumen of most veins has specialized pocket valves that prevent blood from moving in the opposite direction.
Capillaries
What is the difference between arteries and veins, we figured out. And now let's pay attention to the smallest blood vessels - capillaries. They are formed by a special type of integumentary tissue - the endothelium. It is through it that the metabolism between tissue fluid and blood is carried out. Due to this, continuous gas exchange occurs.
Arteries, leaving the heart, disintegrate into capillaries, which approach each cell of the body, merging into venules. The latter, in turn, are connected into larger vessels. They are called veins that enter the heart. In this continuous journey of blood, capillaries play the most important role of direct contact between blood elements and the cells of the whole organism.
Blood movement in the vessels
The difference between arteries and veins is clearly demonstrated by the mechanism of blood flow. During contraction of the heart muscle, blood is expelled with force into the arteries. In the largest of them - the aorta, the pressure can reach 150 mm Hg. Art. In capillaries, it significantly decreases to the level of 20. In the vena cava, the pressure is minimal and amounts to 3-8 mm Hg. Art.
What is tone and blood pressure?
In the normal state of the body, all blood vessels are in a state of minimal tension - tone. If the tone increases, then the blood vessels begin to narrow. This leads to increased pressure. When this condition becomes sufficiently stable, a disease called hypertension occurs. The inverse long process of lowering pressure is hypotension. Both of these diseases are very dangerous. Indeed, in the first case, such a state of blood vessels can lead to a violation of their integrity, and in the second, to a deterioration in the blood supply to organs.
To summarize: how do arteries differ from veins? These are the structural features of the walls, the presence of valves, location in relation to the heart and the functions performed.