Lab2 - Module 1 - Anatomy of the Superficial Back: Page 2 of 3

Muscles connecting the upper limb to the vertebral column – these muscles are extrinsic muscles of the back. They are supplied by the ventral rami of cervical nerves, not by the dorsal rami as one would expect. This is due to the posterior migration of the superficial back muscles during embryonic development. The dorsal primary rami, however, supply sensory to the skin of the back.

Add the Lattimus Dorsi muscle. A large fan shaped muscle that fills the lower half of the back.

Origin - spinous process of the lower six thoracic vertebrae and all five of the lumbar vertebrae, outer lip of the posterior aspect of the iliac crest, and the thoracolumbar fascia.

Insertion - floor of the intertubercular (bicipital) groove.

Innervation - thoracodorsal nerve from the posterior cord of the brachial plexus.

Action - Extension, Adduction, and Medial (Internal) rotation of the humerus at the glenohumeral joint.

Blood supply - thoracodorsal artery from the subscapular artery.

Rotate - the cadaver to visulaize this muscle.

Add the Rhomboid Major muscle. There is a rhomboid major and minor and sometimes they are indistinguishable from each other. Typically, the rhomboid major is about two times wider than the rhomboid minor.

Origin - spinous process of T2 – T5 vertebrae.

Insertion - medial border of scapula.

Innervation - dorsal scapular nerve from the C5 nerve root.

Action - retraction, elevation and downward rotation of the scapula.

Blood supply - deep branch of transverse cervical artery, if present, if not it receives blood from the dorsal scapular artery.

Rotate - the cadaver to visulaize this muscle.

Add the Rhomboid minor muscle.

Origin - ligamentum nuchae and spinous processes of C7 and T1 vertebrae.

Insertion - medial border of scapula.

Innervation - dorsal scapular nerve from the C5 nerve root.

Action - retraction, elevation and downward rotation of the scapula.

Blood supply - deep branch of transverse cervical artery, if present, if not it receives blood from the dorsal scapular artery.

Rotate - the cadaver to visulaize this muscle.

Add the Teres Major muscle. Although it does not connect the vertebral column to the upper limb it is discussed here because of its close relationship with latissimus dorsi. This muscle is technically a scapulohumeral muscle.

Origin - dorsal surface of the inferior angle of the scapula.

Insertion - medial lip of the intertubercular (bicipital) groove.

Innervation - lower subscapular nerve from the posterior cord of the brachial plexus.

Action - Same as latissimus dorsi - Extension, Adduction, and Medial (Internal) Rotation of the humerus at the glenohumeral joint.

Blood supply - circumflex scapular and thoracodorsal arteries.

Rotate - the cadaver to visulaize this muscle.

Add the Teres Minor muscle.

Add the Levator Scapulae muscle. Superior to the Rhomboids and lies deep to the Trapezius.

Origin - transverse processes of the upper four cervical vertebrae.

Insertion - superior angle and superior medial border of the scapula.

Innervation - dorsal scapular nerve from the C5 nerve root and third and fourth cervical nerves.

Action - elevates the scapula and rotates it downward. It also aides in the cervical posture.

Blood supply - transverse cervical artery (both superficial and deep).

Rotate - the cadaver to visulaize this muscle.

The Trapezius Muscle is a large diamond shape muscle of the superficial back that has three sections; Upper, Middle, Lower.

Origin - medial 1/3 of the superior nuchal and external occipital protuberance (upper part); ligamentum nuchae (middle part), and spinous processes of C7 – T12 (lower part).

Insertion - lateral 1/3 of the clavical (upper part); acromion and spine of the scapula (middle part); base of the scapular spine (lower part).

Innervation - spinal root of the Spinal Accessory Nerve (CN XI) and the ventral rami of 3rd and 4th cervical nerves.

Action - Upper part elevates and upwardly rotates the scapula; middle part retracts the scapula; lower part depresses the scapula and rotates upward.

Blood supply - superficial transverse cervical artery.

	Add the Lower Trapezius muscle.
	Add the Middle Trapezius muscle.
	Add the Upper Trapezius muscle.