Serratus posterior superior muscle

At a glance

English

Serratus posterior superior muscle

Latin (TA2)

Musculus serratus posterior superior

System

Muscle

Region

Back

Side

Paired, left and right

Inserts on

The fifth rib, fourth rib and third rib

About the serratus posterior superior muscle

Serratus posterior superior is a thin, quadrilateral muscle at the back of the upper chest. It lies deep to the rhomboids and over the splenius and erector spinae muscles, and it belongs with serratus posterior inferior to the intermediate layer of back muscles, which run between the spine and the ribs.

It begins as an aponeurosis from the lower nuchal ligament, the spines of C7 to T2, sometimes T3, and the supraspinous ligament between them. Its fibres run down and outward and divide into four fleshy slips that attach to the upper borders of ribs 2 to 5, a little beyond their angles.

Contraction lifts the upper ribs, which enlarges the chest and may help in deep breathing in. Like its lower partner, it is a weak muscle, and some authors think its main role is to signal rib position rather than to move the ribs. Its upward pull on the ribs is opposed by serratus posterior inferior acting on the lower ones. Its thin aponeurosis also helps to hold the deeper splenius muscles in place.

It is supplied by ventral rami of T2 to T5, through the upper intercostal nerves, and its blood comes from the posterior intercostal arteries. It is sometimes blamed for pain under the upper part of the scapula, and the area can be reached only when the scapula is drawn forward.

Attachments, action and supply

Origin

Lower nuchal ligament, spines of C7 to T2 (sometimes T3) and the supraspinous ligament.

Insertion

Upper borders of ribs 2 to 5, just lateral to their angles.

Action

Raises the upper ribs; may assist deep breathing in.

Nerve supply

Ventral rami of T2 to T5 (upper intercostal nerves).

Blood supply

Posterior intercostal arteries of the upper spaces.