The muscles of the back can be divided into 3 groups :
- Superficial – associated with movements of the shoulder.
- Intermediate – associated with movements of the thoracic cage.
- Deep – associated with movements of the vertebral column.
The deep muscles develop embryologically in the back & are thus described as intrinsic muscles. The superficial and intermediate muscles do not develop in the back & are classified as extrinsic muscles.
The superficial back muscles are situated underneath the skin and superficial fascia. They originate from the vertebral column & attach to the bones of the shoulder – the clavicle, scapula & humerus. All these muscles are therefore associated with movements of the upper limb.
The muscles in this group are the trapezius, latissimus dorsi, levator scapulae & the rhomboids. The trapezius & the latissimus dorsi lie the most superficially, with the trapezius covering the rhomboids and levator scapulae.