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.
A. Superficial muscles of the back. B. Movements of the scapula.
TABLE 1-1.Superficial Muscles of the Back ||Download (.pdf) TABLE 1-1. Superficial Muscles of the Back
|Muscle ||Proximal Attachment ||Distal Attachment ||Action ||Innervation |
|Trapezius ||Occipital bone, nuchal ligament, and spinous processes of C7–T12 vertebrae ||Spine of scapula, acromion, and lateral third of clavicle ||Elevates, retracts, depresses, and upwardly rotates scapula ||Motor: spinal root of accessory n. (CN XI); proprioception: cervical nn. (C3–C4) |
|Levator scapulae ||Transverse processes of C1–C4 vertebrae ||Medial border of the superior angle of scapula ||Elevates and rotates scapula; lateral flexion of the neck ||Dorsal scapular n. (C5) |
|Rhomboid major ||Spinous processes of T2–T5 vertebrae ||Medial margin of scapula ||Retracts scapula ||Dorsal scapular n. (C5) |
|Rhomboid minor ||Spinous processes of C7–T1 vertebrae ||Medial margin of scapula ||Retracts scapula ||Dorsal scapular n. (C5) |
|Latissimus dorsi ||Spinous processes of T7 sacrum, thoracolumbar fascia, iliac crest, and inferior ribs ||Intertubercular groove of humerus ||Extends, adducts, and medially rotates humerus ||Thoracodorsal n. (C6–C8) |
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.
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