 |
| Cardiovascular system anatomy |
The cardiovascular system and the lymphatic system are collectively called the vascular system, which is a closed continuous pipeline system in the human body. The cardiovascular system consists of the heart, arteries, veins, and capillaries. There is blood circulation inside, and the driving force for blood flow is the heart.
The heart has four lumens, namely: right atrium, right ventricle, left atrium, left ventricle. The left and right half hearts are separated from each other by the septum, and the rooms and rooms on the same side are connected by the mouth of the room. The atrium receives veins, the ventricles emit arteries, and there are valves at the atrioventricular and arterial ports. They act as valves when the blood flows, ensuring that blood flows in one direction in the heart.
The arteries are emitted from the ventricles and transport blood to the blood vessels in various parts of the body. The arteries continue to branch on the way to various parts of the body; the finer and finer, the finer the blood vessels in the tissue and intercellular movements.
A vein is a blood vessel that directs blood back to the atria. The venule originates from the capillaries. During the process of returning to the heart, the lumen becomes thicker and thicker, and finally merges into the large vein and injects into the atria.
Capillaries are tiny blood vessels in the organs. The average diameter of the tube is 7 to 9 microns, which can be seen by means of a microscope. It is extremely abundant in the tissue between the small artery and the small vein. It is almost everywhere, and the capillary wall is extremely thin and transparent. Slow flow in the capillaries facilitates the exchange of substances and gases between the blood and tissues and cells.
Oxygen and nutrients are transported to tissues and cells by systemic circulation. Blood circulation can be divided into two types, systemic circulation and pulmonary circulation, depending on its circulation path.
The circulation path of the systemic circulation is contracted by the left ventricle, and blood (arterial blood) is injected into the aorta; then the branches of the ascending aorta, aortic arch, and descending aorta reach the capillaries of various parts of the body. Because the capillary wall is very thin, the permeability is strong, and the blood flow is slow, it can exchange substances with surrounding tissues and cells. The nutrients and oxygen in the blood flow are absorbed by tissues and cells, and the metabolites of tissues and cells. The carbon dioxide enters the bloodstream, so that the blood turns from bright red arterial blood to dark red venous blood. Capillaries gradually merge into various veins, and finally merge into the superior and inferior vena cava and flow back to the right atrium and then into the right ventricle. Because the systemic circulation is long in the body and has a wide range of tissues and cells, it is also called a large circulation.
The main function of the systemic circulation is to transport nutrients and oxygen to tissues and cells in various parts of the body, and to transport the metabolites of cells and tissues to the excretory organs to ensure the normal metabolism of tissues and cells.
There is oxygen in the blood that allows normal metabolism of cells and tissues in all parts of the body. How is oxygen in the blood obtained? It is obtained by relying on another cycle of circulation in the body, the pulmonary circulation.
The way of pulmonary circulation is: the venous blood (dark red) returned to the right heart by the system circulation. When the ventricle contracts, the blood is injected into the pulmonary artery from the left ventricle, and the blood is introduced into the pulmonary artery by the right ventricle. Branching, and finally shifting between the alveoli to act on the capillaries, the concentration of oxygen in the pulmonary capillaries is low and the concentration of carbon dioxide is high. The oxygen inhaled from the air into the alveoli through the trachea and bronchus is high and the concentration of carbon dioxide is low, so the oxygen pressure in the alveoli is higher than the oxygen pressure in the capillaries around the alveoli. Under normal conditions, the gas is diffused from a high pressure to a low pressure. Therefore, carbon dioxide in the inter-alveolar capillaries diffuses into the alveoli, and oxygen in the alveoli diffuses into the capillaries. After the blood is exchanged in the lungs, the venous blood is turned into arterial blood with high oxygen content (bright red). The venous venules in the lungs merge into a pair of left and right pulmonary veins. After the lungs are injected into the left atrium, the blood flows from the left atrium into the right ventricle. The blood circulates through the above-mentioned pathways. The pulmonary circulation is short in the body, also known as the small circulation. Its main function is to convert the venous blood with low oxygen content in the human body into oxygen-rich arterial blood, so that the blood can obtain oxygen.
The heart of a person's life always beats rhythmically, and once the heartbeat stops, it will "death." Because once the heart suddenly stops beating for some reason, the blood can not circulate in the body, the cells and tissues of the whole body can not get oxygen and nutrients, and its metabolites can not be excreted and accumulated in the body, causing tissue and cells to denature and die. Individual organs and systems are unable to perform their respective physiological functions. For example, the digestive system has no function of digesting and absorbing nutrients; the urinary system does not produce urine or urinate; the respiratory system cannot exchange gas with the outside; the nervous system does not respond to external stimuli. In a word, all human systems and organs have stopped normal physiological activities, and life has ended. Therefore, people must protect the heart from rhythmically, ensuring that blood circulates continuously throughout the cardiovascular system.
The heart is located in the mediastinum of the chest, between the left and right lungs. Wrapped in the heart. About 2/3 is on the left side of the body midline and 1/3 is on the right side of the midline. The long axis of the heart is at an angle of 45° to the midline of the human body. The front of the heart is flat against the sternum and the 2nd to 6th costal cartilage. The posterior direction is the 5th to 9th thoracic vertebrae. The upper part is connected with the large vessel pulmonary trunk, aorta, superior vena cava, pulmonary vein, etc., and the lower part is adjacent to the iliac crest.
The position of the heart in the body may be slightly changed due to the position of the person, the rise and fall of the diaphragm during breathing exercise, and the size of the person. For example, the heart of the short-skinned person is horizontal, the elongated type is vertical, and the moderate is oblique. When inhaling, the diaphragm is lowered, the heart is vertical, and the diaphragm is lifted when exhaling. However, regardless of the position or size of the person, under normal circumstances, the position of the heart is always 2/3 of the "eccentricity" position on the left side of the body's median line.
The human body has a cardiovascular system and a lymphatic system, collectively referred to as the vasculature. The lymphatic system includes:
1 lymphatic vessels that transport lymphatic lymphocytes, lymphatic vessels, lymphatic trunks, and lymphatic ducts;
2 lymphoid tissue distributed in the respiratory tract and digestive tract wall;
3 Lymphoid organs with lymphoid tissue as the main structure, such as lymph nodes, spleen, thymus and sputum tonsils. The fluid flowing in the lymphatic channels of each level is called lymph, which comes from the tissue fluid in the interstitial space.
The word "lymph" is the transliteration of the Latin Lympha, meaning pure and clear water. The lymph is absorbed by the capillary lymphatic vessels, collected by lymphatic vessels at all levels and “filtered” by multi-stage lymph nodes, collected into the left and right lymphatic vessels through the lymphatic trunk (also called the thoracic duct on the left), and finally injected into the left and right jugular veins of the neck. The horn is returned to the vein. Since the capillaries absorb the tissue fluid into the venules and return to the heart through the systemic venous return, why should the lymphatic system absorb the tissue fluid? This is because the liquid in the plasma and most of the components in it ooze out into the interstitial space to become tissue fluid, and the amount of liquid is much larger than the amount of fluid absorbed by the capillaries and the posterior venules of the capillaries, that is, in the tissue. There are still unabsorbed excess liquids in the gap, including macromolecular substances that cannot be absorbed by capillaries and large cells or foreign bodies. The wall structure of capillary lymphatic vessels is incomplete and capillary. Larger, the pressure inside the tube is lower than the osmotic pressure of the tissue fluid, so excessive liquid, protein, fat, bacteria, foreign matter, cancer cells, etc. in the tissue fluid can enter the capillary lymphatic vessels. Because lymph nodes enter the veins before passing through all levels of lymph nodes, bacteria, foreign bodies (such as dust particles inhaled by the lungs), cancer cells, etc. are "detained" by lymph nodes, ensuring that lymph is "clean" when lymphatics enter the blood, lymph nodes and other lymph nodes. Organs produce lymphocytes that are transported to the bloodstream during the lymphatic cycle. It can be seen that from the perspective of body fluid reflux, the lymphatic system is an indispensable auxiliary device for venous return. If there is too much tissue fluid, edema may occur due to venous or lymphatic reflux disorder. From the perspective of human defense function, lymphoid organs in the lymphatic system have the function of producing lymphocytes, filtering lymph and phagocytizing foreign bodies, protecting blood from pathogens and cancer. The "contaminated" barrier of cells has important immune functions.
No comments:
Post a Comment