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During inhalation, the diaphragm contraction causes an increase in the thoracic cavity volume. This decreases the pressure inside the lungs, forcing the air to flow into the lungs. During exhalation, the diaphragm relaxation causes a decrease in the thoracic cavity volume. The increased lung pressure pushes the air out of the lungs. [2]
The diaphragm is the most important muscle of respiration, [3] and separates the thoracic cavity, containing the heart and lungs, from the abdominal cavity: as the diaphragm contracts, the volume of the thoracic cavity increases, creating a negative pressure there, which draws air into the lungs. [4]
Air enters the lungs as the diaphragm strongly contracts, but unlike during traditional relaxed breathing the intercostal muscles of the chest do minimal work in this process. The belly also expands during this type of breathing to make room for the contraction of the diaphragm. [3]
Diaphragmatic excursion is the movement of the thoracic diaphragm during breathing. Normal diaphragmatic excursion should be 3–5 cm, but can be increased in well-conditioned persons to 7–8 cm. This measures the contraction of the diaphragm. It is performed by asking the patient to exhale and hold it.
The lungs are not capable of inflating themselves, and will expand only when there is an increase in the volume of the thoracic cavity. [6] [7] In humans, as in the other mammals, this is achieved primarily through the contraction of the diaphragm, but also by the contraction of the intercostal muscles which pull the rib cage upwards and outwards as shown in the diagrams on the right. [8]
The muscles of respiration are the muscles that contribute to inhalation and exhalation, by aiding in the expansion and contraction of the thoracic cavity. The diaphragm and, to a lesser extent, the intercostal muscles drive respiration during quiet breathing. The elasticity of these muscles is crucial to the health of the respiratory system ...
The normal relaxed state of the lung and chest is partially empty. Further exhalation requires muscular work. Inhalation is an active process requiring work. [4] Some of this work is to overcome frictional resistance to flow, and part is used to deform elastic tissues, and is stored as potential energy, which is recovered during the passive process of exhalation, Tidal breathing is breathing ...
The respiratory pump is a mechanism to pump blood back to the heart using inspiration. It aids blood flow through the veins of the thorax and abdomen.. During inhalation, the volume of the thorax increases, largely through the contraction of the diaphragm, which moves downward and compresses the abdominal cavity.