The respiratory system is composed ofrespiratory tractandlungform.Respiratory tract includesnose、pharynx、throat、tracheaanda bronchial tubeEtc.Usually called nose, pharynx and throatUpper respiratory tract, trachea and bronchi at all levels arelower respiratory tract。The lung consists ofPulmonary parenchymaandPulmonary interstitiumComposition, the former includesBronchial treeandAlveoli；The latter includesconnective tissue, blood vesselslymph glandLymph nodes and nerves.The main function of the respiratory system is to exchange gases, that is, inhale oxygen and exhale carbon dioxide.In addition, the respiratory system also has the functions of pronunciation, smell, neuroendocrine, assisting venous blood to return to the heart and participating in the metabolism of certain substances in the body.[2]
Physiological function and structural characteristics
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In the respiratory system, each organ has a certain division of labor. From the nose to the bronchi at all levels, it is responsible for transmitting gas. The nasal cavity has the functions of warming, wetting and cleaning the air, and can also produce resonance in pronunciation.
The pharynx is a muscular conduit, its upper part is connected with the nasal cavity and oral cavity, and its lower part is connected with the throat and trachea. It is the common channel for food and gas.The trachea is composed of more than ten "C" shaped cartilage rings and smooth muscle between them. The cartilage keeps the trachea open and keeps the gas unobstructed.Smooth muscle can change the caliber of the trachea, which is conducive to the expansion of the esophagus behind it and facilitates food descending.There are glands in the mucosa of trachea and bronchus, which can secrete mucus containing a variety of immunoglobulins (antibodies), with antibacterial and antiviral effects;Moreover, there are cilia on the surface of mucosal epithelial cells, which can constantly swing to the direction of the throat, move the mucus with dust up, and finally cough out of the body to form sputum.Phlegm contains a lot of bacteria and viruses, so do not spit everywhere to pollute the environment.
The larynx is a special part of the respiratory tract and has the function of pronunciation.
The lung is the most important organ in the respiratory system.The adult lung contains 300 to 400 million alveoli. It is formed by repeated branching of bronchioles. Its wall is thin, composed of single-layer epithelial cells, surrounded by capillary networks, and is a place for gas exchange.The chest cavity expands and shrinks rhythmically, which is called respiratory movement, and it depends on the contraction and relaxation of respiratory muscles.The respiratory rhythm is controlled by the central nervous system.The diaphragm is the most important respiratory muscle, which lies between the thorax and the abdomen. When contracting, it enlarges the upper and lower diameters of the thorax, producing inspiration, and when relaxing, it produces exhalation.Vital capacity refers to the amount of gas exhaled as much as possible after maximum inspiration, reflecting the maximum potential of each lung ventilation.It can be measured with a spirometer.The air capacity of the left and right lungs of healthy adult men is about 5000-6500 ml, and that of women is smaller than that of men.
The structure of the respiratory system is characterized by the use of bone or cartilage as a scaffold. When air enters and exits, the tube wall of the respiratory tract will not collapse, making the air flow unimpeded.There are three protective barriers in the whole respiratory tract. First, nasal hair blocks bacteria, viruses and dust from entering the respiratory tract;Second, the mucus secreted by the tracheal epithelial cells sticks the dust and expels it with the cilia movement of the mucosal epithelium;Third, there is a cell in the alveoli that can engulf the dust in the alveoli.The three barriers ensure that the gas exchanged is clean.The human body exchanges gas with the outside world by means of the respiratory system. The air enters the alveoli from the respiratory tract, and the oxygen in the air enters the blood in the capillaries from the alveoli, and is circulated throughout the body for use by tissues and cells.At the same time, carbon dioxide generated by tissue metabolism is transported to the lungs through blood circulation and discharged from the body through the respiratory system.
Clinical etiology
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The proportion of inhalable particulate matter (PM10) in the global atmosphere is not large, but it has an important impact on the environment, climate and human health, so it has attracted much attention.Due to its small particle size and large specific surface area, inhalable particles have strong adsorption and are easy to become carriers of various toxic substances in the air.Particulates are inhaled into the lungs and some remain in the blood, causing respiratory diseases such as colds, asthma, upper respiratory tract infections, pneumonia, tracheitis, etc.
A large number of studies have shown that temperature is one of the most important factors affecting respiratory diseases, and the relationship between temperature and mortality or morbidity of the population shows a J-shaped or U-shaped distribution characteristics. When the temperature is relatively appropriate, the number of deaths or morbidity is the least, but the number of deaths increases with the increase or decrease of temperature.In addition to the health effect of temperature, the humidity in the environment also plays an important role in the occurrence and development of respiratory diseases. When people are exposed to extreme humidity, the death risk of respiratory diseases will also increase.
