Serratus posterior inferior muscle
|Serratus posterior inferior muscle|
Muscles connecting the upper extremity to the vertebral column (serratus posterior inferior labeled at center right).
Serratus posterior inferior (red) seen from back.
|Origin||Vertebrae: Spinous processes of T11 - L2|
|Insertion||The inferior borders of the 9th through 12th ribs|
|Nerve||Intercostal nerves T9 through T12|
|Actions||Depress the lower ribs, aiding in expiration|
|Latin||Musculus serratus posterior inferior|
|Anatomical terms of muscle|
Origin and insertion
It is situated at the junction of the thoracic and lumbar regions: it is of an irregularly quadrilateral form, broader than the serratus posterior superior muscle, and separated from it by a wide interval.
Passing obliquely upward and lateralward, it becomes fleshy, and divides into four flat digitations, which are inserted into the inferior borders of the lower four ribs, a little beyond their angles.
The serratus posterior inferior draws the lower ribs backward and downward to assist in rotation and extension of the trunk. This movement of the ribs also contributes to forced expiration of air from the lungs.
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