By respiration is meant:
Higher plants, which also respire, do not possess any special organs for the gas exchange. They absorb atmospheric oxygen through the stomata and distribute it to the individual plant cells through their intercellular system. Animals have developed diverse potentials to receive vital oxygen. One distinguishes:
In humans, the term respiration denotes the drawing of breath by the expansion and contraction of the ribcage (chest breathing) and the diaphragm (abdominal breathing). Thereby, the breath is drawn in through the airways into the lungs, where the gas exchange takes place.
During respiration, the air is drawn in through the mouth or nose into the body. When respired through the nose, the air is at first cleaned, moistened and warmed by the mucosae and hairs. Subsequently, the air passes along the pharyngeal cavity, larynx and vocal cords to the windpipe (trachea). The windpipe passes on to both branches of the bronchi, which branches out again (bronchioles). At the end, it reaches the alveoli in the lungs, whose fine membranes transfer the oxygen into the capillary vessels and in return releases carbon dioxide from the blood into the lungs. (See also: Respiratory tract)
During inhalation (inspiration), the volume of the ribcage increases by the constriction of the chest muscles and the diaphragm. Thereby, the lungs expand causing a low pressure, and air flows into the lungs.
The pleurae (located between the lungs and the ribcage) and the diaphragm respectively allow the lungs to expand with the ribcage. The membrane surrounding the lungs and on the inner side of the ribcage (pleura) as well as on the diaphragm and the pleura parietalis stick to each other like glass plates with a liquid in between. On the one hand, this enables the repositioning of the concerned structures, and on the other, respectively hinders a collapse of the lung during low pressure and enables its expansion. During exhalation (expiration), the lungs constrict again causing high pressure and the air goes out through the airways.
The respiration is controlled by the brain and the breathing center in the medulla oblongata. The reaction of the chemo receptors to the carbon dioxide content (and/or carbon dioxide partial pressure) of the blood is the crucial factor. If it rises above a certain threshold value, the stimulus to breathe is initiated. Receptors, which react to the pH value of the arterial blood as well as to the lack of oxygen (hypoxia), have only a secondary significance as a stimulus to breathe.
The breathing rate and the tidal volume serve as measurements of the breathing regulation. The breathing rate, which is the number of the inhalation and exhalation of air, amounts to
The tidal volume of a resting adult amounts to between 0.4 and 0.6 liters.
The respiratory disorders are summarized as R06 in the ICD 10 under the symptoms pertaining to the circulatory system and the respiratory system. (The following examples serve primarily only as basics!)
Synonym: cellular respiration
Internal respiration is the release of energy from compounds that can metabolize after gaining energy. Thereby the redox equivalents such as NADH or FADH2 emerge, whose energy can be transferred to ATP in another step by oxidation of the inhaled oxygen.
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