Intermediate Back Muscles: The intermediate back muscles perform a respiratory action and comprise of muscles connected to the ribs. There are three intermediate intrinsic back muscles –1. Iliocostalis 2.Longissimus 3.Spinalis.
Together these muscles form a column, known as the erector spinae.
Iliocostalis: Origin, Insertion, Nerve Supply & Action
The iliocostalis muscle is located laterally in erector spinae. The iliocostalis is associated with the ribs and divided into three parts – lumborum, thoracic, and cervicis.
Attachments:
Origin:
Arises from the common tendinous origin
Insertion:
Inserted to the costal angle of the ribs and the cervical transverse processes.
Nerve supply: Posterior rami of the spinal nerves.
Function: Acts unilaterally vertebral flexion. And acts bilaterally to extend the vertebral column and head.
Longissimus: Origin, Insertion, Nerve Supply & Action
The longissimus is situated between the iliocostalis and spinalis. The longissimus muscle is the largest of the three columns. It divided into three parts – thoracic, cervicis and capitis.
Attachments:
Origin:
Arises from the common tendinous origin
Insertion:
Attaches to the lower ribs, the transverse processes of C2 – T12, and the mastoid process of the skull.
Nerve supply: Posterior rami of the spinal nerves.
Function: Acts unilaterally vertebral flexion. And acts bilaterally to extend the vertebral column and head.
Spinalis: Origin, Insertion, Nerve Supply & Action
The muscle is located medially within the erector spinae. Spinalis is the smallest of the three muscle columns. It divided into the thoracic, cervicis and capitis.
Attachments:
Origin: Arises from the common tendinous origin
Insertion: Attaches to the spinous processes of C2, T1-T8 and the occipital bone of the skull.
Nerve supply: Posterior rami of the spinal nerves.
Function: Acts unilaterally vertebral flexion. And acts bilaterally to extend the vertebral column and head.