External intercostal muscle
Updates to Article Attributes
The external (or outermost) intercostal muscles are an important muscle of respiration. They number eleven on each side and are located in the intercostal space, which expand expanding the transverse dimension of the thoracic cavity during inspiration.
Gross anatomy
The external intercostal muscles are the outermost muscle of the three intercostal muscles and arise from the lower border of the rib above the space. The fibres run in a downwards, forwards and medial direction and insert into the outer lip of the superior border of the rib below. At their insertion they end in thin anterior intercostal membranes that continues towards the sternum. Anteriorly the lower muscles become continuous with the external oblique muscles in the anterolateral abdominal wall. As their name indicates, they are external to the internal intercostal muscles.
Blood supply
- arterial supply: internal thoracic artery and segmental intercostal arteries
- venous drainage: internal thoracic vein and intercostal veins
Nerve supply
Muscular branches from the intercostal nerves of the respective intercostal space (T1-T11), which run with the intercostal vessels under the costal groove in between the internal and innermost intercostal muscles.
Action
External intercostal muscle contraction causes expansion of the thoracic cavity in the transverse dimension and causes an influx of air into the lungs during inspiration. They are stronger than the internal intercostal muscles.
-<p>The <strong>external </strong>(or<strong> outermost</strong>)<strong> intercostal muscles</strong> are an important muscle of respiration. They number eleven on each side and are located in the <a href="/articles/intercostal-spaces">intercostal space,</a> which expand the transverse dimension of the thoracic cavity during inspiration.</p><h4>Gross anatomy</h4><p>The external intercostal muscles are the outermost muscle of the three <a href="/articles/intercostal-muscles">intercostal muscles</a> and arise from the lower border of the <a href="/articles/rib">rib</a> above the space. The fibres run in a downwards, forwards and medial direction and insert into the outer lip of the superior border of the rib below. At their insertion they end in thin anterior intercostal membranes that continues towards the <a href="/articles/sternum">sternum</a>. Anteriorly the lower muscles become continuous with the <a href="/articles/external-oblique-muscles">external oblique muscles</a> in the anterolateral abdominal wall. As their name indicates, they are external to the <a href="/articles/internal-intercostal-muscles">internal intercostal muscles</a>.</p><h4>Blood supply</h4><ul>- +<p>The <strong>external </strong>(or<strong> outermost</strong>)<strong> intercostal muscles</strong> are an important muscle of respiration. They number eleven on each side and are located in the <a href="/articles/intercostal-spaces">intercostal space,</a> expanding the transverse dimension of the thoracic cavity during inspiration.</p><h4>Gross anatomy</h4><p>The external intercostal muscles are the outermost muscle of the three <a href="/articles/intercostal-muscles">intercostal muscles</a> and arise from the lower border of the <a href="/articles/rib">rib</a> above the space. The fibres run in a downwards, forwards and medial direction and insert into the outer lip of the superior border of the rib below. At their insertion they end in thin anterior intercostal membranes that continues towards the <a href="/articles/sternum">sternum</a>. Anteriorly the lower muscles become continuous with the <a href="/articles/external-oblique-muscles">external oblique muscles</a> in the anterolateral abdominal wall. As their name indicates, they are external to the <a href="/articles/internal-intercostal-muscles">internal intercostal muscles</a>.</p><h4>Blood supply</h4><ul>
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