external intercostal muscle

ex·ter·nal in·ter·cos·tal mus·cle

(eks-tĕr'nal in'tĕr-kos'tăl mŭs'ĕl)
Flat muscle of thorax arising from lower border of one rib and passing obliquely downward and forward to be inserted into upper border of rib below; action, contracts during inspiration to elevate ribs; also serves to maintain tension in intercostal spaces to resist inward movement during inspiration; nerve supply, intercostal.
Synonym(s): musculus intercostalis externus.
References in periodicals archive ?
Both the external intercostal muscles and the intercondral elevate the ribs, thus increasing the width of the thoracic cavity, while the diaphragm contracts to increase the vertical dimensions of the thoracic cavity, and also aids in the elevation of the lower ribs.
The main muscles of inspiration are the diaphragm, external intercostal muscles, and accessory muscles of the shoulder and the upper back.
Thus, also stimulating external intercostal muscles or abdominal muscles is not necessary to maintain adequate alveolar ventilation in a nonexercising, paralyzed individual [4].
Contraction of the external intercostal muscles pulls the ribs outward, thereby preventing the inward movement of the upper rib cage; the net effect is to augment the volume of inspired air (Figure 3).
During inspiration, the external intercostal muscles elevate the sternum and anterior thorax increasing the anterior-posterior diameter.

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