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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 ...
These muscles work in unison when inhalation occurs. The internal intercostal muscles relax while the external muscles contract causing the expansion of the chest cavity and an influx of air into the lungs. Each arises from the lower border of a rib, and is inserted into the upper border of the rib below.
The muscle fibers are directed downwards, forwards and laterally forming right angle with external intercostal muscle. Innermost intercostal muscle also known as intercostalis intimus are deep layers of the internal intercostal muscles which are separated from them by a neurovascular bundle. The muscle fibers are directed downwards, forwards ...
The diaphragm is the main muscle of respiration and functions in breathing. During inhalation, the diaphragm contracts and moves in the inferior direction, enlarging the volume of the thoracic cavity and reducing intra-thoracic pressure (the external intercostal muscles also
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]
The muscles of forceful breathing (inhalation and exhalation). The color code is the same as on the left. In addition to a more forceful and extensive contraction of the diaphragm, the intercostal muscles are aided by the accessory muscles of inhalation to exaggerate the movement of the ribs upwards, causing a greater expansion of the rib cage.
During inhalation, the volume of the thorax increases, largely through the contraction of the diaphragm, which moves downward and compresses the abdominal cavity. The elevation of the chest caused by the contraction of the external intercostal muscles also contributes to the increased volume of the thorax.
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.