Iliocostalis

The iliocostalis is a deep muscle located laterally within the erector spinae complex of the back, comprising three parts: lumborum, thoracis, and cervicis. It plays a crucial role in the movement and stability of the vertebral column.

The iliocostalis muscle originates from the lower thoracic and lumbar vertebrae, sacrum, posterior aspect of the iliac crest, and associated ligaments. It inserts at the costal angles of the ribs and the transverse processes of the cervical vertebrae.

The iliocostalis muscle laterally flexes the vertebral column when acting unilaterally and extends the vertebral column and head when acting bilaterally. This dual functionality is vital for maintaining posture and facilitating movement.

The iliocostalis muscle is innervated by the posterior rami of the spinal nerves, which provide the necessary motor control for its actions. This innervation is essential for the muscle's role in spinal movement and stability.

The blood supply to the iliocostalis muscle varies by region: the iliocostalis cervicis receives blood from the occipital, deep cervical, and vertebral arteries, while the thoracis is supplied by the dorsal branches of the posterior intercostal and subcostal arteries. The iliocostalis lumborum is nourished by the dorsal branches of the lumbar and sacral arteries.