Muscles of shoulder region Flashcards
Two divisions of muscles
Extrinsic
Intrinsic
Extrinsic muscles
Originate from torso (back of trunk) and insert onto bones of shoulder (clavicle, scapula, humerus)
Intrinsic muscles
Originate from scapula/clavicle and insert onto humerus
Extrinsic muscles named
Superficial: trapezius and lattisimus dorsi
Deep: levator scapulae, rhomboid major and minor
Trapezius O and I
O: occipital protuberance of skull, nuchal ligament, spinous processes C7-T12
I: Clavicle, acromion and spine of scapula
Trapezius action
Upper fibres elevate scapula and rotate during abduction above 90 degrees
Middle fibres retract scapula
Lower fibres pull scapula inferiorly
Trapezius innervation
Spinal accessory nerve (cranial nerve XI)
Proprioceptor fibres C3 C4
test trapezius
Shrug shoulders while someone is pushing down on them
Latissimus dorsi O and I
Deep to inferior fibres of trapezius
O: Spinous processes T6-T12, iliac crest, thoracolumbar fascia, inferior 3 ribs
I: Tendon into intertubercular sulcus of humerus
Actions and innervation lattisimus dorsi
Action: extends, adducts and medially rotates the shoulder joint
Innervation: Thoracodorsal nerve
Levator scapulae O and I
O: Tranverse processes C1-C4
I: Medial border of scapula
(deep to trapezius and superior to rhomboid minor)
Innervation and action levator scapulae
Action: elevates scapula
Innervation: Dorsal scapular nerve
Rhomboids
Rhomboid minor is superior to major but is smaller
Rhomboid minor O and I
O: Spinous processes C7-T1
I: Medial border scapula
Rhomboid minor action and innervation
Action: Retracts scapula rotates medial border (back to anatomical position after abduction above 90 degrees)
innervation: Dorsal scapular nerve
Rhomboid major o and I
O: Spinous processes T2-T5
I - medial border scapula
Rhomboid major actions and innervations
Actions: Retracts scapula, rotates medial border (glenoid fossa rotated inferiorly, helps return to anatomical position after 90 degree+ abduction)
Innervation; Dorsal scapular nerve
Intrinsic muscles known as
Scapulohumeral group
Deltoid O and I
o: lateral 3rd anterior border clavicle, acromion and spine of scapula
I: deltoid tuberosity on humerus
Deltoid actions
Anterior fibres: Flex and medially rotate arm at shoulder
Middle fibres: abduct arm from 15-90 degrees
Posterior fibres: extend and laterally rotate arm at shoulder
Deltoid innervation
Axillary nerve
Teres major O and I
O; Posterior inferior angle scapula
I: Medial lip of intertubercular groove
(inferior border of quadrangular space: axillary nerve and posterior circumflex humeral artery pass)
Teres major action and innervation
Action: adducts and extends arm at shoulder, medially rotates arm
Innervation: Lower subscapular nerve
(goes from posterior and inserts anteriorly)
Rotator cuff muscles
Originate from scapula
Attach to humeral head
Pull humeral head into glenoid fossa
Rotator cuffs (4)
SITS
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
Supraspinatus O and I
O: Supraspinous fossa of scapula
I: greater tubercle of humerus
Supraspinatus action and innervation
A: Abducts arm first 15 degrees
I: Suprascapular nerve
Infraspinatus O and i
O; Infraspinous fossa of scapula
I: Greater tubercle of humerus (between supraspinatus and teres major)
Infraspinatus A and I
A: Laterally rotates arm
I: Suprascapular nerve
Subscapularis O and I
O: subscapular fossa
I: LESSER tubercle of humerus
Subscapualris A and I
A: medially rotates
I: Upper and lower subscapular nerves
Teres minor O and I
O: Posterior scapula
I: Greater tubercle humerus
Teres minor A and I
A: Laterally rotates arm
I: Axillary nerve
