There are several main tissues and systems in the human body. What are their names, structures and functions?

Eight systems: circulatory system, respiratory system, endocrine system, urinary system, reproductive system, nervous system, exercise system and digestive system. The main systems of human body are immune system, respiratory system, circulatory system, digestive system, nervous system, musculoskeletal system, epidermal system, endocrine system, reproductive system and eyes. Under the interaction of these systems, the human body can carry out daily activities. Without these systems, even a seemingly simple action can't be completed. Balanced nutrition and healthy lifestyle can ensure the normal operation of these systems and maintain good health. Answer: The immune system is a reticular system composed of bone marrow, thymus, lymph, tonsil, spleen, cecum and many immune cells. All over the human body, it can automatically fight against foreign harmful substances and remove necrotic cells. Its main function is to help the body resist the invasion of pollutants, viruses and bacteria. In addition, the immune system can also prevent genetic errors that may occur during cell replication, which is the main cause of tumors and cancers. A: The respiratory system helps the human body to complete the most critical action-breathing. It shoulders the heavy responsibility of filtering the inhaled air and protecting the lungs from foreign harmful substances. Inhalation of oxygen, a seemingly simple action, will bring many dangers to the human body. A normal person breathes more than 2,000 gallons of air every day, but there are about 20 billion foreign particles in the air, including dust, pollen, chemicals, and various viruses and bacteria that can cause diseases. The respiratory system consists of respiratory tract (nose, throat, trachea and bronchus) and lungs. Every time you breathe, the immune function of the respiratory system works at the same time to ensure that foreign harmful substances do not reach the lungs. Vesicular macrophages are an excellent example of resisting the invasion of foreign harmful substances. It is like a competent "garbage collector", as long as harmful microorganisms are found to enter the lungs, they will be removed immediately. In fact, macrophages have the same function in all parts of the human body. A: The circulatory system consists of veins, arteries and capillaries. Driven by a powerful heart, it works hard all the time to provide oxygen and various nutrients for all parts of the human body. Besides carrying oxygen and maintaining life, a healthy circulatory system can also regulate blood pressure and help transport immune cells. The human immune system is like a powerful army, protecting human health. White blood cells, phagocytes and macrophages are all extremely effective soldiers. A healthy circulatory system provides a smooth path for the entire immune system, enabling this powerful army to quickly destroy invading bacteria and microorganisms. On the contrary, if the circulatory system is not smooth, it will weaken the fighting ability of the immune system. Once a large amount of fat accumulates in veins and arteries, it will not only reduce human immunity, but also lead to various heart diseases. A: If food is the energy of the human body, then the digestive system is a "gas station" that converts food into energy. The digestive system includes mouth, esophagus, stomach and intestine, all of which play an important role in this transformation process-breaking down nutrients in food and then distributing them to all parts of the body. However, food not only provides energy for the human body, but also brings certain dangers to the digestive system. The biggest threat is that the food people eat contains substances harmful to human body. Therefore, the human immune system will also help the digestive system resist these harmful substances. For example, the gastric acid secreted by immune cells, mucosa and stomach in the digestive tract has the function of killing harmful microorganisms. A: The nervous system directly or indirectly controls all other systems of the human body. The nervous system includes: brain, spinal cord, nerves and nerve cells. Nerve cells, also known as neurons, can send radio waves with information to the whole body, thus telling people how to act, how to think and how to react. One of the most important duties of the nervous system is to regulate immune function. Its influence on the immune system includes both physiological and psychological aspects. Physiological effects involve neural channels connecting the brain and the immune system; The psychological influence is that the human immune system is more active and healthy in an optimistic and positive mental state. A: The musculoskeletal system consists of bones, ligaments, tendons and muscles. Its main function is to support the body and provide guarantee for the systematic operation of human organs. A very important function of bone tissue is to make blood cells. The hard surface of bones provides a protective layer for the production of blood cells. The red bone marrow in the outer layer of leg bone, hip bone and sternum is the source of circulatory system, white blood cells and other blood cells. The ancestors of cells, usually called stem cells, will develop into many different kinds of immune cells, such as granulosa cells, monocytes and lymphocytes. A: The outer skin system is the body's "armor"-skin. The human body is attacked by millions of particles every day and polluted by the surrounding environment. Skin, hair, nails and film are the first line of defense against these harmful substances. Without this solid protection, pathogens will flood into the human body, and those organs and tissues that are vital to maintaining human life will have to be tackled with folded arms. The outermost layer of skin is called epidermis, which has the function of regeneration. The stratum corneum, or keratin, can secrete sweat and acidic sebum, which will destroy many microorganisms as soon as they touch the skin. A: The endocrine system consists of submandibular gland, thyroid gland, adrenal gland, hypothalamus, pancreas, ovary, testis and other special tissues. The function of these glands and organs is to secrete hormones and have the function of assisting the human body. Hormones are of great significance to the human body, so we must take good care of the endocrine system. Mental stress or infection can affect the concentration of hormones in the blood. Corticosteroid is a special hormone secreted by adrenal gland. Once produced too much, it will have a negative impact on the human immune system. Like other human systems, the endocrine system is protected by immune cells such as macrophages, and it also makes great contributions to the immune system: providing information links between the brain and the immune system. A: Female reproductive system includes fallopian tube, cervix, vagina and other organs, while male reproductive system includes testis, penis, scrotum and other organs. In fact, the defensive function of the reproductive system is the strongest in the human body. In order to prevent infectious organisms from entering women through the reproductive tract, it has set up a strict defense net after another. The acidic substances contained in the mucus secreted by vaginal wall, white blood cells and cilia in reproductive tract can effectively kill invasive harmful microorganisms. However, in order to facilitate the passage of sperm, the protective mucus on the vagina and uterus will become extremely thin during ovulation. During pregnancy, the fetus in the mother's womb is threatened by her own immune system. Because the embryo contains two different genetic materials from the father and the mother, the mother's immune system regards it as a "foreign body" and produces antibodies to attack it. Fortunately, the uterus can prevent most antibodies from entering and protect the fetus from the mother's natural defense.