Trunk (thorax, abdomen, back)

Spinalis Thoracis

Musculus spinalis thoracis

Origin

Spinous processes of T11-L2

Insertion

Spinous processes of the upper thoracic vertebrae (approximately T4-T8)

Function

Extension of the thoracic spine, part of erector spinae

Innervation

Dorsal rami of the thoracic spinal nerves

Movement & chain

Works together with longissimus thoracis and iliocostalis thoracis (together forming erector spinae) in holding the trunk upright and extending it.

Palpation

Palpable as a narrow muscular cord immediately adjacent to spinous processes T1–T8.

Clinical

Medial column of erector spinae producing pure thoracic extension; fatigued and hypertonic in thoracic hyperkyphosis.

Segmental innervation

Dorsal rami T4-L2.

In clinical practice

Ergonomic patient repositioning (log-roll technique in spinal trauma) and pressure offloading; maintain neutral spinal alignment in bedridden patients.

Region in the model

Trunk (thorax, abdomen, back)