Serratus posterior inferior muscle

The serratus posterior inferior muscle, also known as the posterior serratus muscle,^{[citation needed]} is a muscle of the human body.

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 [edit on Wikidata]

Structure

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]}

Function

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]

Additional images

• 
  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

See also

• Serratus anterior muscle
• Serratus posterior superior muscle