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SUPERFICIAL BACK MUSCLES

BIG PICTURE

The superficial back muscles consist of the trapezius, levator scapulae, rhomboid major, rhomboid minor, and latissimus dorsi muscles (Figure 1-1A; Table 1-1). Although these muscles are located in the back, they are considered to be muscles of the upper limbs because they connect the upper limbs to the trunk and assist in upper limb movements via the scapula and humerus. Because these are upper limb muscles, they are innervated by the ventral rami of spinal nerves (brachial plexus branches), with the exception of the trapezius muscle (which is innervated by CN XI). These muscles are discussed in greater detail in Section VI, Upper Limb, but are included here because these muscles overly the deep back muscles.

Figure 1-1:

A. Superficial muscles of the back. B. Movements of the scapula.

TABLE 1-1.Superficial Muscles of the Back

TRAPEZIUS MUSCLE

  • Topography. The most superficial back muscle; has a triangular shape, with three unique fiber orientations giving rise to multiple actions.

  • Proximal attachment(s). Occipital bone, nuchal ligament, spinous processes of C7–T12.

  • Distal attachment(s). Scapular spine, acromion, and clavicle.

  • Action(s). Scapular elevation (superior fibers); scapular retraction (middle fibers), and scapular depression (lower fibers); upward rotation (all fibers working together).

  • Innervation. Spinal accessory nerve (CN XI), which arises from the spinal cord, ascends through the foramen magnum into the skull and descends through the jugular foramen along the deep surface of the trapezius.

LEVATOR SCAPULAE MUSCLE

  • Topography. Located deep to the trapezius muscle and superior to the rhomboids.

  • Proximal attachment(s). Transverse processes of upper cervical vertebrae.

  • Distal attachment(s). Superior angle of the scapula.

  • Action(s). Elevation and downward rotation of the scapula.

  • Innervation. Dorsal scapular nerve (C5); branches from C4–C5 ventral rami.

RHOMBOID MAJOR AND MINOR MUSCLES

  • Topography. Located deep to the trapezius ...

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