Name

# Serratus Posterior Inferior

Pronunciation

(ser-RA-tus pos-TEER-I-or in-feer-i-or)

Origin/Proximal Attachment

Spines of T11-L2 or L3

Insertion/Distal Attachment

Ribs 9-12

Action/Relevance

Draws the ribs back & downward. Acting unilaterally, they assist with lateral flexion of the trunk.

Innervation

T9-12

Notes

The Serratus posterior inferior (Serratus posticus inferior) is situated at the junction of the thoracic and lumbar regions: it is of an irregularly quadrilateral form, broader than the preceding, 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 vertebrę, 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.