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Position of the serratus posterior inferior (shown in red). Animation. -
Close up. The muscle arises from the vertebrae T11 through L2 and inserted into lower border of the 9th through 12th ribs. -
Lumbar triangle
| 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. | |
| Details | |
| Origin | Vertebrae: Spinous processes of T11 - L2 |
| Insertion | The inferior borders of the 9th through 12th ribs |
| Artery | Intercostal arteries |
| Nerve | Intercostal nerves T9 through T12 |
| Actions | Depress the lower ribs 9-12, aiding in expiration |
| Identifiers | |
| Latin | musculus serratus posterior inferior |
| TA98 | A04.3.01.010 |
| TA2 | 2235 |
| FMA | 13402 |
| Anatomical terms of muscle | |
The serratus posterior inferior muscle, also known as the posterior serratus muscle,[citation needed] is a muscle of the human body.
The muscle is situated at the junction of the thoracic and lumbar regions.[1] It has an irregularly quadrilateral form, broader than the serratus posterior superior muscle, and separated from it by a wide interval.
It arises by a thin aponeurosis from the spinous processes of the lower two thoracic and upper two or three lumbar vertebrae.[1]
Passing obliquely upward and lateralward, it becomes fleshy, and divides into four flat digitations.[1] These are inserted into the inferior borders of the lower four ribs, a little beyond their angles.[1]
The thin aponeurosis of origin is intimately blended with the thoracolumbar fascia, and aponeurosis of the latissimus dorsi muscle.[citation needed]
The serratus posterior inferior draws the lower ribs backward and downward to assist in rotation and extension of the trunk.[1] This movement of the ribs may also contribute to inhalation and forced expiration of air from the lungs.[2]
