The superficial back muscles lie just under the skin and fascia. They connect the spine to the bones of the shoulder - the clavicle, scapula, and humerus - and help move the upper limb.

These muscles include:

• Trapezius

• Latissimus dorsi

• Levator scapulae

• Rhomboid major and minor.

The trapezius and latissimus dorsi are the most visible on the surface, while the rhomboids and levator scapulae lie underneath.

During fetal development, these muscles actually migrated from the upper limb to the back, which is why they are sometimes called immigrant muscles.
They are divided into two groups:

All are controlled by the anterior (ventral) rami of cervical spinal nerves, except the trapezius, which is innervated by the accessory nerve (cranial nerve XI).

Trapezius

The trapezius is a large, triangular muscle covering the upper back and neck. Both sides together form a trapezoid shape. 

• Origin: Skull, nuchal ligament, and spinous processes from C7–T12.

• Insertion: Lateral third of the clavicle, acromion, and spine of the scapula.

• Innervation: Accessory nerve (CN XI), with sensory input from spinal nerves C3 and C4.

Its upper fibers: Lift (elevate) and rotate the scapula during arm raising.

Its middle fibers: Pull (retract) the scapula backward.

Its lower fibers: Pull the scapula downward (depress it).

Overall, the trapezius stabilizes, elevates, retracts, and rotates the scapula. When acting alone, it can also tilt or extend the head.

Latissimus Dorsi

The latissimus dorsi is the widest muscle in the body, covering the lower back. It extends, adducts, and medially rotates the arm; it helps pull the body upward (as in climbing or rowing).

• Origin: Spinous processes of T6–T12, thoracolumbar fascia, iliac crest, and lower ribs.

• Insertion: Intertubercular groove of the humerus.

• Innervation: Thoracodorsal nerve (C6–C8).

Levator Scapulae

The levator scapulae is a small, strap-like muscle that runs along the side of the neck. It elevates the scapula and helps bend (laterally flex) or extend the neck.

• Origin: Transverse processes of C1–C4.

• Insertion: Upper part of the medial border of the scapula.

• Innervation: Dorsal scapular nerve (C5).

Rhomboids (Major and Minor)

The rhomboids are two small, rectangular muscles under the trapezius that connect the spine to the scapula.
They work together to retract and rotate the scapula.

Rhomboid Major

• Origin: Spinous processes of T2–T5.

• Insertion: Medial border of the scapula (between spine and inferior angle).

• Innervation: Dorsal scapular nerve (C5).

Rhomboid Minor

• Origin: Spinous processes of C7–T1.

• Insertion: Medial border of the scapula at the level of the spine.

• Innervation: Dorsal scapular nerve (C5).

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