Muscles of the Back

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Layers of the Muscles of the Back

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Terms in this set (25)

1st Layer = Superficial Extrinsic Muscles
—w/ attachments to the pectoral girdle or upper limb,
—act on upper limb

2nd Layer = Intermediate Extrinsic Muscles
—attaching to ribs
—accessory muscles of respiration

3rd Layer = Intrinsic Back Muscles
—divided into Superficial, Intermediate, & Deep
—mostly acting on the vertebral column & skull

Trapezius Muscle

O = superior Nuchal line, external occipital protuberance, ligamentum nuchae & spinous processes (C7 - T12)

I = Lateral 1/3 of clavicle, and acromion & spine of scapula

A= elevates, retracts, superiorly rotates & depresses scapula (depends on which fibers contract)

Inv = motor via accessory nerve (CN 11) and sensory via rami of C3 & C4 spinal nerves

Latissimus Dorsi Muscle

O = Spinous processes of lower 6 thoracic vertebrae, and the lumbar & sacral vertebrae, iliac crest, lower 3 or 4 ribs; (
(attachments to vertebrae and iliac crest are established via thoracolumbar facia)

I = Tendon inserts to floor of intertubercular (bicipital) groove of humerus

A = Extends, abducts, & medially rotates arm

Inv = thoracodorsal nerve (branch of brachial plexus)

Levator Scapulae muscle

O = transverse processes of upper 4 cervical vertebrae

I = Medial border of scapula (from superior angle to root of spine)

A = elevates & rotates scapula inferiorily

Inv = Ventral rami of C3 & C4 spinal nerves, and dorsal scapular nerve (branch of brachial plexus)

Rhomboid Major Muscle

O = spinous processes from T2 - T5

I = medial border of scapula (from root of spine to inferior angle)

A = retract & help rotate scapula inferiorly (same as minor)

Inv = dorsal scapular nerve (branch of brachial plexus) (same as minor)