Breathing is a complex multi-stage physiological process, the essence of which is the absorption of oxygen from the environment for its subsequent participation in redox reactions.
However, it is inherent not only to higher animals, but also to all aerobic organisms, including unicellular ones, and therefore it can be said that this is the main way to obtain macroergic compounds. The energy generated during breathing is then expended on the numerous needs of the body. About 20% of all oxygen is consumed by the brain, as a lot of substrates are spent on carrying out high-speed pulses. In humans, breathing proceeds in two large phases: external respiration (this is the process of gas exchange between the walls of the alveoli of the lungs and capillaries) and internal - the further transport of oxygen to all cells and tissues.
Cell level breathing
However, the first is the result of the work of organs and tissues, but cellular respiration is already a process at the molecular and atomic levels, in which oxygen is necessary for the electron transfer chain with the removal of the negative charge from O2 and the formation of water and high-energy compounds. Also, for the continuous occurrence of these reactions, specialized proteins and a proton donor are needed. The respiration of higher organisms and the respiration of organisms, as measured by micrometers, vary significantly. So, bacteria differ in 3 types of relationship to oxygen. Strict aerobes receive molecular oxygen directly: they use bound oxygen (carbon dioxide, sulfur oxide, etc.), while molecular oxygen is destructive for them. The mixed type of respiration in facultative bacteria implies the possibility of using both bound and molecular oxygen, depending on the conditions.
Human respiratory mechanisms
So, external respiration is a process that is carried out thanks to the structure of the airways and the work of the muscles of the chest and diaphragm, as a result of which the pressure in the lungs drops, the gases move inside. Exhalation is the reverse process in which air (mainly carbon dioxide) comes out. Normally, the gas flow through the respiratory tract is laminar, that is, parallel to the walls of the bronchi, and when obstacles arise (obstruction by a foreign object, accumulation of mucus), turbulent turbulence occurs. The blood is saturated with oxygen precisely in the lungs, after which it, oxygenated, is transported through the capillaries, collected in larger vessels and ultimately enters the heart. From there, it leaves the aorta and enters a large circle of blood circulation.
Pathology
It is necessary to distinguish between the concepts of breathing and ventilation. The second is the process of contraction of the intercostal and deep muscles of the chest to change its size, the movement of air along the trachea and bronchi to the alveoli. In turn, breathing is a process no less active, but means gas exchange at the alveolar-capillary level. The causes of poor ventilation can be diseases with damage to the respiratory tract, chest deformities, obstruction or restriction (emphysema, bronchial asthma, bronchitis), systemic scleroderma. Massive ventilation of the lungs can also be due to pathological conditions: infection, pharmacological effects of drugs, state of overexcitation, high physical activity.