Serratus Posterior Inferior

General information

There are two serratus muscles, although the most commonly known one is the serratus anterior muscle. The lesser known is the serratus posterior muscle which is located in the upper and lower back’s intermediate layer. This muscle can be further divided into the serratus posterior superior and serratus posterior inferior muscles.

Literal meaning

The lower, back saw-like muscle.

Interesting information

The serratus posterior muscles have a significant role in forced respiration. Their main actions are rib elevation for the serratus posterior superior and rib depression for the serratus posterior inferior, which are necessary movements during the act of respiration.

Origin

Spinous processes of vertebrae T11-L2.

Insertion

Inferior borders of ribs 9-12.

Function

Depresses ribs

Draws ribs inferoposteriorly.

Nerve supply

Anterior rami of spinal nerves T9-T12.

Blood supply

Posterior intercostal arteries, the subcostal artery and upper lumbar arteries.

Relevant research

There is inconclusive research on the roles of both serratus posterior muscles as no concrete evidence has been found to support their role in respiration, or in proprioception, another proposed action of these muscles.

Vilensky, J. A., Baltes, M., Weikel, L., Fortin, J. D., & Fourie, L. J. (2001). Serratus posterior muscles: anatomy, clinical relevance, and function. Clinical anatomy (New York, N.Y.), 14(4), 237–241.

Serratus posterior inferior exercises

None specific to this muscle.