Most of the organs located in the body cavity are directly or indirectly communicated with the outside world, including digestive, respiratory, urinary and reproductive systems. According to its morphological structure, it can be divided into lumen organs and parenchymal organs.
The lumen organs are all connected with the outside world by pipes; The parenchymal organ is mainly a gland, with a catheter opening in the wall of the lumen organ. From the point of ontogeny, most of the digestive system and respiratory system are derived from endoderm; The respiratory organ is another tube that protrudes from the upper part of the primitive digestive tube to the ventral side.
The urinary and reproductive organs originated from the urogenital ridge of mesoderm, and evolved into urinary and reproductive systems with different functions. However, there is still a common discharge tube in men. Therefore, some people refer to the urinary and reproductive systems as urogenital systems.
The structure diagram of human internal organs is as follows:
Extended data
I. Classification:
(1) Digestive system:
The general name of digestive organs, which consists of digestive tubes and digestive glands.
The digestive tract of human body is long and tortuous, including mouth, pharynx, esophagus, stomach, small intestine, large intestine and anus. Among them, the small intestine is the longest and the most important place to digest and absorb nutrients, with a total length of 5~7 meters. It is coiled in the middle and lower part of the abdominal cavity and is divided into duodenum, jejunum and ileum in turn.
The duodenum is about the same length as 12 fingers together, about 25~30 cm. Because the lumen receives acidic chyme, pancreatic juice and bile propelled by the stomach, some people refer to the duodenum as the "Yangtze River Delta" of the digestive system.
There is no obvious boundary between jejunum and ileum, jejunum accounts for 2/5 and ileum accounts for 3/5. The large intestine is connected to the back of the small intestine, with a total length of 1.5 m, and is divided into three parts: cecum, colon and rectum.
Digestive glands are divided into two categories: one is located outside the digestive tract; Macrodigestive glands visible to the naked eye, such as salivary glands, liver and pancreas, all have ducts opening into the digestive tract, and the secreted digestive juice can flow into the digestive tract through the ducts. The other is the small glands distributed in the digestive tract wall, which can only be seen under the microscope, such as stomach glands and intestinal glands.
The energy needed by the human body in various physiological activities and the raw materials needed by the body in growth, development and tissue renewal are all supplied by food, and the nutrients contained in food must be digested and absorbed by the digestive system before they can be used by the human body. Food enters the mouth, is chewed by the teeth and stirred by the tongue, is mixed with saliva, and flows into the stomach along the esophagus through glossopharyngeal action.
Stay in the stomach for 3 ~ 5 hours, fully mix with gastric juice for preliminary digestion, and push chyme into the small intestine through the movement of the stomach. After entering the small intestine, various nutrients in food are digested and absorbed under the action of various digestive enzymes. The remaining food scraps enter the large intestine and are finally excreted.
(2) Respiratory system:
It is the floorboard of respiratory organs, which consists of respiratory tract and lung. The respiratory tract is a passage for gas to enter and leave the lungs, which consists of nose, pharynx, larynx, trachea and bronchus. The lung is the main organ of the respiratory system and the place for gas exchange.
The human body must constantly absorb oxygen from the outside and exhale carbon dioxide from the body. This process of gas exchange between the human body and the outside world is completed by the respiratory system. The whole process of breathing can be completed only if the respiratory system cooperates with the circulatory system, while aerobic breathing and anaerobic breathing are carried out inside the cells.
(3) Urinary system:
A system consisting of a group of organs that produce, transport, store and excrete urine. Human urinary system includes kidney, ureter, bladder and urethra. When blood passes through the kidney, water and some substances (mainly metabolites) in the blood are filtered out through the glomerulus, then stored in the bladder through the renal pelvis and ureter. When urinating, the bladder muscles contract and urine is discharged through the urethra.
(4) Reproductive system:
Anatomical name. It is a general term for organs that reproduce offspring and continue the race. The organs of the reproductive system are different between men and women, but they are all composed of gonads, reproductive ducts and accessory organs according to their functions. Reproductive organs can reproduce through their various activities, fertilization, pregnancy and other physiological processes.
Second, the blood supply:
The vascular supply of internal organs is abundant. Some organs have special blood circulation. For example, the lung has two sets of blood circulation: systemic circulation and pulmonary circulation. The former supplies nutrition, while the latter is related to the intake of O2 and the discharge of CO2. Another example is that the volume of the kidney is not large, but the input arterial blood and the derived venous blood are extremely large, which is related to the function of the kidney to "filter" the whole body blood around the clock.
Another example is the gastrointestinal capillaries, which gradually merge into hepatic portal vein, and the venous blood containing nutrients is carried into the liver. The portal vein is subdivided into capillaries (sinuses) in the liver to contact each liver cell, and then merged into hepatic veins and injected into the inferior vena cava.
The characteristics of portal vein, a double capillary, are related to the absorption of nutrients in the intestine and their transportation to the liver for processing and storage. In a word, the blood circulation characteristics of an organ reflect its function. Visceral muscles are mainly smooth muscles, which are dominated by autonomic nerves (sympathetic and parasympathetic nerves), and glands are also dominated by autonomic nerves, so the movement of most visceral organs and the secretion activities of all glands are not dominated by will.