Serratus posterior inferior muscle
Muscles connecting the upper extremity to the vertebral column. (Serratus posterior inferior labeled at center right.)
Gray's	subject #117 404
Origin	vertebrae T11 - L3
Insertion	the inferior borders of the 9th through 12th ribs
Artery	intercostal arteries
Nerve	intercostal nerves T9 through T12
Actions	depress the lower ribs, aiding in expiration

The Serratus posterior inferior muscle (or posterior serratus) is a muscle of the human body.

Contents 1 Origin and insertion 2 Function 3 See also 4 External links

[edit] Origin and insertion

The muscle lies at the junction of the thoracic and lumbar regions. It arises from the vertebrae T11 through L2 and runs superolaterally to attach to the lower border of the 9th through 12th ribs.

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.

It arises by a thin aponeurosis from the spinous processes of the lower two thoracic and upper two or three lumbar vertebræ, and from the supraspinal ligament.

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 thin aponeurosis of origin is intimately blended with the lumbodorsal fascia, and aponeurosis of the Latissimus dorsi.

[edit] Function

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.

[edit] See also

• Serratus anterior muscle
• Serratus posterior superior muscle

[edit] External links

• LUC spi
• SUNY Figs 01:05-04 - "Intermediate layer of the extrinsic muscles of the back, deep muscles."
• Cross section at UV pembody/body8a

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.

v • d • e List of muscles of torso (TA A04.3-5, GA 4.397) Back splenius (capitis, cervicis) · erector spinae (iliocostalis, longissimus, spinalis) · latissimus dorsi transversospinales: (semispinalis dorsi, semispinalis cervicis, semispinalis capitis, multifidus, rotatores) · interspinales · intertransversarii Vertebral column: trapezius · latissimus dorsi · rhomboid (major, minor) · levator scapulae fascia: Thoracolumbar fascia Thorax intercostales (external, internal, innermost) · subcostales · transversus thoracis · levatores costarum · serratus posterior (inferior, superior) · diaphragm Thoracic cavity: pectoralis major · pectoralis minor · subclavius · serratus anterior fascia: Pectoral fascia · Clavipectoral fascia Abdominopelvic Abdomen/ wall Anterior/ lateral Abdominal external oblique · Transversus abdominis/Conjoint tendon · Rectus sheath (rectus abdominis, pyramidalis) · Arcuate line · Tendinous intersection Cremaster · Abdominal internal oblique Fascia/abdominal fascia: panniculus adiposus (Fascia of Camper) · stratum membranosum (Fascia of Scarpa) · Transversalis fascia (Interfoveolar ligament) Linea alba · Linea semilunaris · Inguinal triangle Inguinal canal (Deep inguinal ring, Superficial inguinal ring, Intercrural fibers, Crura of superficial inguinal ring) Inguinal ligament (Pectineal ligament, Lacunar ligament, Reflected ligament) Posterior quadratus lumborum · psoas major/psoas minor · iliacus  · iliopsoas fascia (Iliac fascia/Iliopectineal arch) Pelvis levator ani (iliococcygeus, pubococcygeus, puborectalis) · coccygeus fascia/pelvic fascia visceral (Rectovaginal fascia, Rectoprostatic fascia) · parietal (Obturator fascia/Tendinous arch, Piriformis fascia) floor/diaphragm: Superior fascia of pelvic diaphragm (Pubovesical ligament, Puboprostatic ligament) · Inferior fascia of pelvic diaphragm Anococcygeal body

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