Muscles - Shoulder (extrinsic) Flashcards
What are extrinsic shoulder muscles?
These muscles originate from the torso and attach to the shoulder (clavicle, humerus or scapular).
What are the superficial muscles?
1) Trapezius
2) Latissimus dorsi
Trapezius
Origin - skull, nuchal ligament, spinous process (C7 - T12)
Insertion - clavicle, acromion and scapula spine.
Innervation - motor - accessory nerve
Proprioceptive fibres - C3-C4
Action:
1) Elevate the scapula
2) Rotate scapula in abduction
3) Middle fibres retract the scapula
4) Lower fibres depress the scapula
Clinical relevance: testing the accessory nerve
Aetiology - iatrogenic (e.g. cervical lymph node biopsy or cannulation of the internal jugual vein).
To test accessory, trapezius function can be assessed. Ask the patient to shrug his/her shoulders.
Other features: muscle wasting, partial paralysis of sternocleidomastoid, and an assymetrical neckline.
Latissimus dorsi
Origin - spinous process (T7-T12), iliac crest, thoracolumbar fascia, inferior three ribs.
Insertion - converge into a tendon to attach to the intertubercular sulcus.
Innervation - thoracodorsal nerve
Function:
1) Extends
2) Adducts
3) Medially rotate the upper limb
What are the deep muscles?
These are the levator scapulae and rhomboids.
Levator scapulae
Origin - transverse process (C1-C4)
Insertion - medial border of scapula
Innervation - dorsal scapular nerve
Actions - elevates the scapula
Rhomboid major
Located inferior to the rhomboid minor.
Origin - spinous process (T2-T5),
Insertion - medial border of scapula, between spine and inferior angle.
Innervation - dorsal scapular nerve
Function - Retracts and rotate the scapula
Rhomboid minor
Located superior to the rhomboid major.
Origin - Spinous process (C7-T1)
Insertion - medial border of scapula, at the level of spine of scapula.
Innervation - dorsal scapula nerve
Actions - retracts and rotates scapula
