Shoulder muscles

Question 1

Trapezius

Answer 1

Origin:

• Superior nuchal line,
• External occipital protuberance,
• Medial margin of the ligamentum nuchae,
• Spinous processes of C7 to T12
• The related supraspinous ligaments

Insertion:

• Superior edge of the crest of the spine of the scapula,
• Acromion,
• Posterior border of lateral one third of clavical

Innervation:

• Motor spinal part of accessory nerve (XI)
• Sensory anterior rami of C3 and C4.

Function:

• Powerful elevator of the scapula
• Rotates the scapula furing abduction of humerus above horisontal
• Middle fibres retract scapula
• Lower fibres depress scapula

Question 2

Deltoid

Answer 2

Origin:

• Inferior edge of the crest of the spine of the scapula
• Lateral margin of the acromion
• Anterior border of lateral one thrid of the clavical

Inserion:

• Deltoid tuberosity of the humerus

Innervation:

Axillary nerve

Function:

• Major abductor of arm (beyond 15 degrees (after supraspinatus))
• Clavicular fibres assist in flexing the arm
• Posterior fibres assist in extending the arm

Question 3

Levator scapulae

Answer 3

Origin:

• Transverse processes of C1 to C4

Insertion:

• Upper portion of medial border of scapula

Innervation:

• C3 to C4 and dorsal scapular nerve

Function:

• Elevates the scapula

Question 4

Rhomboid minor

Answer 4

Origin:

• Lower end of ligamentum nuchae
• Spinous processes of C7 and T1 vertebrae

Insertion:

• Posterior surface of medial border of scapula at the root of the spine of the scapula

Innervation:

• Dorsal scapula nerve [C4, C5]

Function:

Elevates and retracts the scapula

Question 5

Rhomboid major

Answer 5

Origin:

• Spinous processes of TII-TV vertebrae
• Intervening supraspinous ligaments

Insertion:

• Posterior surface of medial border of scapula from the root of the spine of the scapula to the inferior angle

Innervation:

Dorsal scapular nerve (C4, C5)

Function:

Elevates and retracts the scapula