Back Muscles

Question 1

Deltoid Muscle

Answer 1

O: acromion, spine of scapula, clavicle
I: deltoid tuberosity of humerus
In: anterior and posterior branch of axillary nerve (C5, C6)
Fx: flexes, abducts, extends +lat rotates arm

Question 2

Supraspinatus Muscle

Answer 2

O: Supraspinous fossa of scapula
I: Superior facet of greater tubercle of humerus
In: suprascapular nerve (C5, C6)
Fx: initiates arm abduction, acts with rot cuff muscles

Question 3

Infraspinatus Muscle

Answer 3

O: Infraspinous fossa of scapula
I: Mid facet of greater tubercle of humerus
In: Suprascapular nerve (C5, C6)
Fx: lat rotation of arm (w. teres minor)

Question 4

Teres Minor Muscle

Answer 4

O: Lateral border of scapula
I: Inferior facet of greater tubercle of humerus
In: Posterior branch of axillary nerve (C5, C6)
Fx: lat rotation of arm, aDDuction

Question 5

Teres Major Muscle

Answer 5

O: Inferior angle of scapula
I: Medial lip of intertubercular sulcus
In: Inferior subscapular nerve (C5, C6)
Fx: aDDucts, medial rotation

Question 6

Trapezius Muscle (upper, middle, lower)

Answer 6

Upper
O: External occipital protrub, spines C7-T12
I: acromion, clavicle, spine of scapula
Fx: elevates (shrug), Upward rot., at rest holds shoulder up and back against gravity. 
Mid
O: lower cervical, upper thoracic spines 
I: scapular spine 
Fx: retracts scapula, upward rot. 
Lower
O: Lower thoracic spines
I: medial end of scapular spine 
Fx: depresses scapula, upward rot.

**In: accessory nerve (cranial nerve XI) and C3-C4 (proprioception)

Question 7

Latissimus Dorsi Muscle

Answer 7

O: Spine T7-T12, lower ribs, iliac crest
I: Humerus- intertubercular sulcus
In: Thoracodorsal nerve (C6-C8)
Fx: extends, adducts, medially rotates arm (same as Teres Major)

Question 8

Rhomboid Major and Minor Muscle

Answer 8

O: Spine T2-T5
I: Medial border of scapula
In: Dorsal scapular nerve (C4-C5)
Fx: Retracts, rotates, fixes scapula (depress glenoid cavity)

Question 9

Levator Scapulae Muscle

Answer 9

O: transverse processes C1-C4
I: medial border of scapula
In: Dorsal scapular nerve
Fx: elevated scapula medially

Question 10

Erector Spinea Muscle

Answer 10

(Deep Back- Iliocostalis, longissimus, spinalis).
O: Sacrum, iliac crest, spines of lower lumbar
In: dorsal rami of spinal nerves
Fx: extend and laterally bend vertebral column and head

Question 11

Serratus Anterior Muscle

Answer 11

O: Anterolateral aspect of upper 8-9 ribs
I: Medial border of scapula
In: Long thoracic nerve (C5, C6)
Fx: Scapular abduction and upward glenoid rotation

Question 12

Subscapularis

Answer 12

O: Subscapular fossa of the scapula
I: Lesser tubercle of humerus
In: Upper and lower subscapular nerve
Fx: Internal rotation of shoulder when no resistance present

Question 13

Pectoralis Major

Answer 13

O: Clavicle, sternum, lower ribs
I: humerus- crest of the greater tubercle
In: Lateral and medial pectoral nerves (C5-C8, T1)
Fx: Shoulder adduction, internal rotation, return of flexed arm to neutral