What is breathing

breathing

Synonyms: breathing, breathing activity, respiratio
English: respiration, breathing

1 definition

breathing is a biological process in which molecular oxygen is absorbed, transported into the cells and reduced to water in the respiratory chain. In return, carbon dioxide is produced and given off.

2 classification

In medicine or biology, according to anatomical-physiological and biochemical aspects, the outer and the inner Breathing (cellular breathing) differentiated:

  • External respiration: The breathing gas exchange that takes place when breathing in the lungs. In doing so, oxygen is absorbed from the environment and carbon dioxide is given off. The product of external breathing is breath.
  • Internal respiration: The biochemical process of cell respiration, in which organic compounds are oxidized into low-energy substances for the purpose of producing ATP.

Only external breathing is discussed below. Internal respiration is discussed under the heading "cell respiration".

3 anatomy

When breathing, the air flows into the body through the airways. Entry can take place through the oral cavity (mouth breathing) or through the nose (nasal breathing).

During nasal breathing, larger foreign bodies are held up by nasal hairs in the area of ​​the nasal entrance. The air you breathe then flows through the nasal cavity, where it is cleaned, moistened and warmed up through the nasal mucous membrane. Via the pharynx, it is carried on to the larynx. There the vocal cords mark the border between the upper and lower airways. The windpipe (trachea) begins caudal to the larynx. It branches distally into two main bronchi, then within the lungs into numerous branches, the bronchi. The even smaller bronchioles arise from them. In order to ensure the removal of foreign bodies that are absorbed with the breath, the airways are lined with a specialized epithelium, the respiratory ciliated epithelium.

Finally, at the end of the airways are the alveoli of the lungs, through whose thin membrane oxygen passes into the capillary vessels and, in the opposite direction, carbon dioxide is released from the blood to the lungs.

For more details see:Respiratory tract, carbon dioxide transport

4 physiology

4.1 Overview

In the course of evolution, animals have developed various ways of getting their vital oxygen. One differentiates:

  • Skin breathing, in which the gas exchange takes place over the entire body surface.
  • Gill breathing, in which the gas exchange takes place via thin, blood-supplied skin protuberances, the gills. It occurs in many invertebrates and in fish.
  • Tracheal breathing via tubular indentations in the skin of the body. It occurs in insects.
  • Lung breathing with the help of bags called lungs that are everted into the body. It occurs e.g. in lung-breathing snails and amphibians, reptiles, birds and mammals including humans.

4.2 Breathing Mechanics

In humans, breathing is the result of coordinated muscle activity that causes the thorax (chest breathing) and the diaphragm (abdominal breathing) to rise and fall. This creates a stream of breath that transports the air through the airways into the lungs, where the actual gas exchange takes place.

During inhalation (inspiration), the activity of the respiratory muscles and auxiliary respiratory muscles increases the volume of the thorax. The lungs expand and a negative pressure is created, air flows through the airways into the lungs. So that the lungs follow the breathing excursions of the thorax, there is a thin serous layer of tissue between the lungs and the chest or diaphragm, the pleura, which consists of two leaves. The lungs are surrounded by the visceral pleura. Opposite it is on the inside of the rib cage, as well as on the diaphragm and the mediastinum, the parietal pleura. Both pleural leaves stick together under the action of capillary forces like two glass plates with a film of liquid between them. On the one hand, this enables the structures involved to move and, on the other hand, prevents the lungs from collapsing or allowing them to unfold due to the negative pressure in the chest cavity.

During exhalation (exhalation), the respiratory muscles relax again and the air flows out through the airways due to the excess pressure. The expiration can also be forced through the active use of the respiratory muscles.

4.3 Breath control

Breathing is controlled by the brain or the breathing center in the medulla oblongata. The decisive factor is the reaction of chemoreceptors to the carbon dioxide content or the carbon dioxide partial pressure of the blood. If this exceeds a certain threshold value, the breathing stimulus sets in. Receptors that react to the pH value of the arterial blood and a lack of oxygen (hypoxia) are only of secondary importance as respiratory stimuli.

see also: Breath regulation

4.4 Tidal volumes

When breathing, one can differentiate between different tidal volumes or lung volumes. These parameters provide, among other things, an overview of the performance reserves of the lungs. The following values ​​refer to an adult of normal weight.

description abbreviation Value (l) description
Tidal volume AZV 0,4-0,5 Volume that is inhaled and exhaled with each breath
Inspiratory reserve volume IRV 2,5-3,0 Volume that can also be inhaled after a normal inspiration
Expiratory reserve volume ERV 1,0-1,5 Volume that can also be exhaled after normal expiration
Vital capacity VK, VC 4,5-5,0 Sum of AZV, IRV and ERV
Residual volume RV 1,5-2,0 Volume that remains in the lungs after maximum expiration
Total capacity TK, TLC 6,0-6,5 Sum of VK and RV
Functional residual capacity FRK, FRC 2,5-3,0 Sum of ERV and RV
Respiratory time volume AMV 8,0-10,0 Product of tidal volume and respiratory rate / minute

4.5 respiratory rate

Another parameter of breathing is the breathing rate. It amounts to

  • Adults 12-15 per minute
  • Teenagers 16-20 per minute
  • Toddler around 25 per minute
  • Infant around 30 per minute
  • Newborns around 40 per minute

5 clinic

5.1 Pathological forms of breathing

Respiratory disorders are listed in the ICD-10 under "Symptoms that affect the circulatory and respiratory systems" in the diagnosis group R06 summarized.

Reduced breathing or lung ventilation is called hypoventilation, and increased ventilation is called hyperventilation. Disturbed breathing is called dyspnea, and the resulting impairment of pulmonary gas exchange is called "respiratory insufficiency". If the breathing stops completely, one speaks of an apnea.


In addition, there are a number of respiratory disorders in which the depth of breath and / or the breathing rhythm is disturbed in a characteristic way. These include:

5.2 Diagnostics

Pathological changes in the respiratory system are clinically recorded by auscultation of the lungs, during which the breath sounds and secondary noises are listened to with the aid of a stethoscope.

Further diagnostic statements are made possible by imaging diagnostics of the lungs (X-ray, MRI, CT) or bronchoscopy. The systematic review and analysis of breathing activity and function is carried out with the help of lung function diagnostics.