Overview of the back muscles anatomy
These muscles are divided into two major groups:
- The superficial (extrinsic) muscles.
- The deep (intrinsic) muscles.
The superficial muscles
These muscles connect the upper limb with the vertebral Colum or inevitably to the trunk, these are:
§ Rhomboid major and minor.
§ Levator scapulae.
§ Latissimus dorsi.
While Serratus posterior superior and inferior form the intermediate layer of muscles, passing from the vertebral spines to the ribs; the two muscles slope in opposite directions and are muscles of respiration.
Trapezius muscle: originates from the external occipital protuberance, superior nuchal line (medially), nuchal ligament, spinous processes and their supraspinous ligaments from C7 to T12. It then inserts to the acromium and posterior lateral 1/3 of the clavicle. Its action is to elevate and steady the scapular, rotates the scapular forward to raise the arm above the head and also retracting the scapular, bracing back the shoulder.
The deep muscles
These are a complex group of muscles extending from the pelvis to the skull. It includes the following: splenius capitis, splenius cervicis, extensor spinae, iliocostalis, longissimus, spinalis, multifidus, rotators, semi-spinalis, interspinalis, and inter-transverse muscles
Note: the iliocostalis, longissimus and spinalis muscles have a common origin which is – the tendon of erector spinae muscle at the sacrum and iliac crest.
It lies medially from iliocostalis muscle and is divided into three groups.
The transversospinalis muscular group consists of the following: semispinalis thoracis, rotators thoracis, multifidus, semispinalis cervicis, rotators cervicis, semispinalis capitis and rotators capitis.
They run obliquely upwards and medially from the transverse processes to adjacent, and sometimes more adjacent, spinous processes.
Semi-spinalis thoracis originate from transverse processes of T6 toT12 and inserts at spinous processes of upper thoracic and most lumber vertebrae.
Cervical region. Articular processes of lower cervical vertebrae.
Thoracic region: transverse processes of all thoracic vertebrae.
Lumber region: Have three portions; the lower portion from the dorsal sacrum, the deep surface from the tendonous part of erector spine and the last portion from mammillary process of lumber vertebra.
Insertion: Spinous process of all vertebrae from C2 to L5.
Action: Bilaterally extends vertebrae column, controls lateral flexion to side opposite contraction and unilaterally rotates vertebral bodies to opposite side.
Rotators: They lie deep to multifidus and are fully developed only in the thoracic region. All rotators originate from transverse process of one vertebrae skip one vertebrae and insert to the spinous process of the above vertebra.
Rotators can also be categorized as short rotators and long rotators, the former attach close vertebrae and the later to the far apart vertebrae.
These are most deep muscles of the back. There are two segmental muscles:
Interspinalis muscles: These lie between spinous processes and they extend through the vertebral column.
Intertransversal muscles: These originate from the posterior and anterior tubercle of transverse processes and insert at the thoracic and lumber lateral aspect of the transverse and mammillary processes.
Lavatory costae longus: Originates from the transverse processes of cervical and thoracic vertebrae and insert at the ribs below them. They elevate the ribs.
All muscles that make up the back muscle anatomy receive their blood supply from the branches of the axillary artery and are innervated by the posterior rami of spinal nerves.