With each breath your organism receives oxygen, deleting at an exhalation a by-product, carbonic gas. This zhiznetvornyj gas exchange name breath.
All living tissues require the constant energy source, developed at fuel burning (carbohydrates, fats or fibers). Fuel burns down, incorporating to oxygen which gets to an organism at a breath and is carried on blood vessels in all cages.
At combustion of oxygen (oxidation) three end-products - energy, water and carbonic gas are formed. With deducing from an organism of unnecessary carbonic gas gas exchange process begins. Blood transfers it to lungs, therefrom it comes back in an environment, and instead of it the new portion of oxygen is inhaled. Respiratory process is rather effectively regulated, therefore concentration of gases in blood is supported in very narrow limits, serving as a guarantee of your health.
The Requirement for oxygen changes depending on degree of activity of an organism. We will tell, the usual adult man at rest inhales about 3,75 l of air a minute. This volume contains 3 oxygen which is acquired approximately on 1/3 about 750 sm. Start up the person after the bus, the got into gear muscles will demand much more some oxygen for what it is necessary to inhale in 15 times more air. Oxygen consumption can increase approximately in 30 times.
As to an organism depending on activity degree different volumes of oxygen, to you not to do without reserve capacity which provides an internal structure of lungs, and in particular, alveoluses are required. Not to manage to you and without constant balance between frequency and depth of breath and blood supply of lungs.
At a breath air at first gets to the top respiratory ways - nasal and a mouth which are connected among themselves and as if a door, separate from each other a soft palate. The oral cavity and nose mucous membrane humidifies and warms air before it will get to lungs, and a cavity of a nose besides is covered by thin hairs on which settles a dust.
Further air gets in short hrjashchevuju a tube, or a throat, and therefrom to a trachea which is divided into two bronchial tubes. Its mucous membrane too warms air and catches a dust.
The Main bronchial tubes are connected to lungs where they are repeatedly divided into small secondary bronchial tubes, on one on each share of a lung. To very few people (except doctors, it is final) that fact that at the left lung two shares, and at right - three is known. Becoming in process of division ever less and already, bronchial tubes form primary, and then final bronhioly which come to an end with the tiny air sacks of alveoluses divided on some compartments.
Bronchial tubes and bronhioly are supplied with blood from branches of the pulmonary artery bearing in lungs poor oxygen blood from right zheludochka of the heart. The artery branches on numerous capillaries through which blood gets to alveoluses. Through walls of these microscopic thin-walled vials red blood little bodies – tiny carriers of a life in difficult structure of our body - grasp the oxygen taken from air and give carbonic gas.
The Blood enriched by oxygen as a result of gas exchange, gets to pulmonary veins and in left zheludochek hearts, whence is pumped over in different bodies of a body.
Lungs are surrounded and protected by a two-layer cover of a pleura. Between its layers there is a narrow gleam, or the pleural cavity containing a small amount of a liquid. This liquid serves as the greasing which is not supposing friction of lungs about a thorax at each breath.
In the course of breath two groups of muscles participate. These are the intercostal muscles filling gleams between edges, and a diaphragm - the wide flat muscle dividing a thorax and a belly cavity. That air has got to lungs, pressure in them should be below atmospheric. The diaphragm is reduced, intercostal muscles move apart edges forward and upwards, expanding space for lungs, and atmospheric air directs in the rarefied area. At an exhalation respiratory muscles relax, and air is pushed out outside.
the Unconditioned reflex
Breath is a reflex action which the respiratory center, group of the nervous cages located in the bottom part of a brain operates. From here nervous impulses go to respiratory muscles, forcing them to extend or be reduced depending on level of oxygen and carbonic gas in blood. Surplus of carbonic gas reduces alkaline reaction of blood, stimulating the respiratory center, and you start to breathe faster and more deeply, exhaling it more. At shortage of carbonic acid your breath becomes superficial and is slowed down until the balance will not be restored.