Extrinsic Muscles of the Back

Question 1

Trapezius

Answer 1

O: med 1/3 of superior nuchal line; external occipital protuberance, ligamentum nuchae; SP of C7-T12;

I: lateral 1/3 of clavicle, acromion, superior fibers more laterally, inferior fibers insert on the spine without extending to acromion

A: Elevates (superior fibers), retracts (middle fibers), rotates superiorly (superior and inferior), and depresses (inferior)

N: spinal accessory n. and cervical n. C3, C4

Question 2

Latissimus Dorsi

Answer 2

O: spinous processes of inf. 6 thoracic vertebrae, thoracolumbar fascia, iliac crest and inferior 3-4 ribs

I: intertubercular groove of humerus

A: extends, A44, and int. rotates humerus; raises body towards arm during climbing

N: Thoracodorsal n. (C6, 7, 8)

Question 3

Levator Scapula

Answer 3

O: post. tubercles of TP of C1-C4

I: superior medial border of scapula

A: elevates scapula, inferiorly rotates

N:dorsal scapular n. (C5) and cervical n. (C3, C4)

Question 4

Rhomboid Minor

Answer 4

O: ligamentum nuchae and SP of C7, T1 vertebrae

I: medial border of scapula from level of spine of scapula to inferior angle

A: retracts scapula and inf. rotates lateral angle, depressing glenoid cavity; fixes scapula

N: dorsal scapular n. (C4, C5)