Extensor spinae

Erector spinae
The erector spinae muscle group
Details
Origin	Spinous processes of T9-T12 thoracic vertebrae, medial slope of the dorsal segment of illiac crest
Insertion	spinous processes of T1 and T2 thoracic vertebrae and the cervical vertebrae
Artery	lateral sacral artery
Nerve	posterior branch of spinal nerve
Actions	extends the vertebral column
Antagonist	rectus abdominis muscle
Identifiers
Latin	Musculus erector spinae
TA	A04.3.02.002
FMA	71302
Anatomical terms of muscle []

The erector spinae (/ɪˈrɛktər ˈspaɪni/ i-REK-tər SPY-nee) or spinal erectors is a set of muscles that straighten and rotate the back.

The erector spinae is not just one muscle, but a bundle of muscles and tendons which run more or less vertically and are paired left to right. These muscles lie in the groove to the side of the vertebral column and extend throughout the lumbar, thoracic, and cervical regions. The erector spinae is covered in the lumbar and thoracic regions by the thoracolumbar fascia, and in the cervical region by the nuchal ligament.

This large muscular and tendinous mass varies in size and structure at different parts of the vertebral column. In the sacral region, it is narrow and pointed, and at its origin chiefly tendinous in structure. In the lumbar region, it is larger, and forms a thick fleshy mass. Further up, it is subdivided into three columns. They gradually diminish in size as they ascend to be inserted into the vertebrae and ribs.

The erector spinae arises from the anterior surface of a broad and thick tendon. It is attached to the medial crest of the sacrum, to the spinous processes of the lumbar and the eleventh and twelfth thoracic vertebrae and the supraspinous ligament, to the back part of the inner lip of the iliac crests, and to the lateral crests of the sacrum, where it blends with the sacrotuberous and posterior sacroiliac ligaments.