The baby began to cry from the moment of birth, and the crying dilated the respiratory tract, and the two lungs suddenly swelled like balloons. Thereafter, he will continue to breathe until the last moment of his life. The process of human breathing is deceptively simple but interlocking, ensuring that every cell receives the selfless gift of nature - oxygen. Oxygen supplies cellular energy through biological oxidation, while producing metabolites such as carbon dioxide. In extreme cases, humans may not eat for 7 days and drink water for 3 days, but they cannot go 5 minutes without breathing. Irreversible necrosis occurs if the brain ischemia and hypoxia occur within 5 minutes.
In a quiet state, adults breathe an average of 16 breaths per minute, inhaling 500 milliliters of air each time (about 21% oxygen). The whole process of breathing includes three links: the first is external breathing, through the breathing movement to make the outside air into the lungs, oxygen through the alveolar wall into the lung capillaries; secondly, the gas is transported in the blood, through the blood circulation to transport oxygen to the tissues of the whole body; and then the internal breathing, that is, gas exchange between blood and cells and intracellular oxidation metabolism. Blocking any of these three links can lead to suffocation: blocking the mouth and nose will block external breathing; gas poisoning will block the transport of gas in the blood, and oxygen will not be able to bind to hemoglobin; cyanide poisoning will block internal breathing, and cells cannot use oxygen.
The human respiratory system has evolved over a long period of time. Primitive organisms exchange gases directly through cell membranes, and it is not until the molluscs that they have a separate respiratory organ, the gills, and the lungs that appear in amphibians. The human respiratory system includes all levels of organs from the nasal cavity, throat, trachea, bronchi to the lungs (collectively known as the respiratory tract), as well as the pleura and mediastinum, which together with blood circulation to complete the task of gas exchange.
The respiratory tract is directly connected with the outside world, and the air is constantly moving in and out with the movement of breathing, which also facilitates the spread of bacteria and viruses. Colds (infections of the nose, pharynx, and larynx) are the most common respiratory diseases, in addition to tracheitis, bronchitis, or pneumonia. In recent years, the spread of SARS virus, avian influenza and new coronavirus is through the respiratory tract, and the incidence of allergic rhinitis, asthma and lung cancer is also increasing year by year. The spread of these diseases warns us that if the environment is not well protected, pollution is reduced, and the ecological balance of nature is maintained, human beings can breathe freely.
Dust and microbes float in the air, but we don't have to be intimidated by the air like birds of prey. The respiratory tract has multiple protective mechanisms and is not easily sick under normal circumstances. These protective mechanisms include: many branches of the respiratory tract, bacteria and viruses can not drive straight in, it is easy to disperse and be surrounded by the immune system; when encountering irritating gases, the smooth muscles of the respiratory tract can contract, which can cause coughing and sneezing, reducing the entry of toxic gases; the respiratory tract can secrete mucus to adhere to foreign bodies, form sputum discharge, so that it does not enter the alveoli; the respiratory tract below the trachea is covered with cilia, and the oscillation of cilia can discharge dust and bacteria. There are also macrophages below the bronchi of grade 17, which can engulf pathogens. With these protective mechanisms, the respiratory tract is generally not invaded by bacteria and viruses. The respiratory tract can only be infected if the protective mechanism is reduced, or when the number of bacteria and viruses is large and the virulence is strong.
Protecting the respiratory tract requires maintaining good work and rest habits, exercising appropriately, paying attention to the intake of foods containing vitamin A or carotene, protecting the epithelium of the respiratory mucosa, maintaining the integrity of cilia, drinking more water in autumn and winter, and keeping the respiratory tract moist.
Air quality and health are very closely related, although it is impossible to buy canned air on the Hulunbuir grassland all year round, but it can minimize the haze weather out, do not smoke, smoke less second-hand smoke, often open windows for ventilation in the living room, use environmentally friendly home improvement materials, and use air purifiers if possible.
The author is an associate professor at Central China Normal University and a director of Hubei Physiological Society
Source: Popular Science Times
Author: Wang Xin
Editor: Wu Tong
Review: Wang Fei
Final Judge: Chen Lei
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