Muscles of the shoulder & Arm Flashcards
What are the muscles of the rotator cuff
Supraspinatus, infraspinatus, teres minor and subscapularis
Supraspinatus action
1) Abduct the shoulder
2) Stabilize head of humerus in glenoid fossa
Supraspinatus origin/insertion
Origin: Supraspinous fossa of scapula (above scap spine)
Insertion: Greater tubercle of humerus (same as infraspinatus & teres minor)
Supraspinatus nerve
Suprascapular nerve - C4-6, innervated by branches from C5 & 6
Infraspinatus action
Same as teres minor!
1) ER shoulder
2) Adduct shoulder
3)Stabilize humeral head in glenoid fossa
Infraspinatus origin & insertion
O: Infraspinous fossa of scap
I: Greater tubercle of humerus (same as teres minor and supraspinatus)
Infraspinatus nerve
Same as supraspinatus: Suprascapular nerve, C4-6 but innervated from the C5 & 6 branches
Teres minor action
Same as infraspinatus!
1) ER shoulder
2) Adduct shoulder
3) Stabilize humeral head in glenoid fossa
Teres minor origin & insertion
O: Upper 2/3 of the lateral border of the scap
I: Greater tubercle of humerus (same as supraspinatus and infraspinatus)
Teres minor nerve
Axillary nerve, C5, C6
Subscapularis action
1) Strong shoulder internal rotator
2) Stabilize the head of the humerus in the glenoid fossa
Subscapularis O & I
O: Subscapular fossa of the scap (anterior scap)
I: Lesser tubercle of the humerus
Subscapularis nerve
Upper and lower subscapular nerve, originating from C5-C7 but subscap just gets the innervation from C5&6 branches
Rhomboid major action
1) Adduct the scap
2) Elevate scap
3) Downwardly rotate scap
Rhomboid major O & I
O: T2-T5 spinous processes
I: Medial border of scap between inferior angle and scapular spine
Rhomboid major nerve
Dorsal scapular nerve (comes from C4/C5 but C5 branch only to rhomboids)
Rhomboid minor action
Same as rhomboid major
1) Adduct scap
2) Elevate scap
3) Downwardly rotate scap
Rhomboid minor O & I
O: C7 & T1 spinous processes
I: Medial border of scap @ and above the scap spine
Rhomboid minor nerve
Dorsal scapular nerve (C4, 5 but rhomboids innervated by C5 branch)
Levator scap action (unilaterally & bilaterally)
Unilaterally:
1) Elevate scap
2) Downwardly rotate scap
3) Laterally flex head & neck
4) Rotate head & neck to same side
Bilaterally:
Extend the head and neck
Levator scap O & I
O: Transverse processes of C1-C4
I: Overlapping with & just above rhomboid minor - medial border of scap between superior portion of scapular spine & superior angle
Levator scap innervation
C3 and C4 primary rami and dorsal scapular nerve C4, C5
Serratus anterior actions (with origin fixed, and with scapula fixed)
Origin fixed:
1) Abduct scapula
2) Upwardly rotate scap
3) Depress scap
4) Hold medial border of scap against rib cage
Scapula fixed:
Elevate the thorax through forced inhalation (accessory resp muscle)
Serratus anterior O & I
O: Lateral aspects of first 8 ribs
I: Anterior surface of medial border of scap, spanning from the inferior all the way to the superior angle (so closer to the medial border from subscap)
Pec major actions
A) All fibers
B) Upper fibers
C) Lower fibers
All fibers:
1) Adduct the shoulder
2) Medially rotate shoulder
3) Elevate thorax with forced inhalation with arms fixed
Upper fibers:
1) Flex shoulder
2) Horizontally adduct shoulder
Lower fibers:
1) Extend shoulder
Pec major O & I
O: Medial 1/2 of clavicle, whole sternum, cartilage of ribs 1-6
I: Crest of greater tubercle of humerus (just inferior to GT)
Pec major innervation (upper & lower fibers)
Upper fibers: Lateral pectoral nerve (originating at C5-7)
Lower fibers: Lateral & medical pectoral nerves (originating C6-T1)
Pec minor action
1) Depress the scapula
2) Abduct the scapula
3) Downwardly rotate the scapula
4) With the scapula fixed, helps to elevate the thorax for forced inhalation
Pec minor O & I
O: 3-5th ribs (anterior portion)
I: Medial surface of coracoid process of scap
Pec minor innervation
Medical pectoral nerve with fibers from a communicating branch of the lateral pectoral nerve (origins C6-T1 but specifically C7&8 for pec min)
Subclavius action
1) Depress clavicle and draw it anteriorly
2) Elevate 1st rib (assist with inhalation)
3) Stabilize the sternoclavicular joint
Subclavius O & I
O: 1st rib & cartilage
I: Inferior surface of middle of clavicle
Subclavius innervation
Subclavian nerve (from C5 & C6)
Biceps brachii action
1) Flex elbow
2) Supinate forearm
3) Flex shoulder
Biceps brachii O & I
O: Short head: Coracoid process of scapula. Long head: Supraglenoid tubercle of scap
I: Radial tuberosity & bicipital aponeurosis
Biceps brachii innervation
Musculocutaneous nerve (C5, C6)
Triceps brachii actions (all heads, long head)
All heads: Extend the elbow
Long head: Extend the shoulder, adduct the shoulder
Triceps brachii origin & insertion
O: Long head: Infraglenoid tubercle of scapula; Lateral head: Posterior surface of proximal half of humerus; Medial head: Posterior surface of distal half of humerus (medial head is shorter than lateral head)
I: All insert at olercranon process of ulna
Triceps brachii innervation
Radial nerve: C6-T1, but triceps receives branches from C7 & C8
Coracobrachialis actions
Flex shoulder
Adduct shoulder (secondary flexor & adductor)
Coracobrachialis O & I
Origin: Coracoid process of scap
Insertion: Medial surface of mid-humeral shaft
Coracobrachialis innervation
Musculocutaneous nerve (C6, C7)
Deltoid actions (all fibers, anterior fibers, posterior fibers)
All fibers: Abduct the shoulder
Anterior fibers: Flex the shoulder, medially rotate the shoulder, horizontally adduct the shoulder
Posterior fibers: Extend the shoulder, laterally rotate the shoulder, horizontally abduct the shoulder
Deltoid O & I
O: Lateral 1/3 of scap, acromion, scapular spine
I: Deltoid tuberosity of humerus
Deltoid innervation
Axillary nerve: C5 & C6
Trapezius actions (upper, middle, and lower)
Upper:
Bilaterally: Extend the head and neck
Unilaterally:
1) Laterally flex head & neck to same side
2) Rotate head and neck to opposite side
3) Elevate the scap
4) Upwardly rotate scap
Middle fibers:
1) Adduct scap
2) Stabilize scap
Lower fibers:
1) Depress scap
2) Upwardly rotate scap
Trapezius O & I
O:
- External occipital protuberance (base of back of head)
- Medial portion of superior nuchal line of occiput (inferior to external occipital protuberance)
- Ligamentum nuchae (ligament running from External occipital protuberance to C7)
- Spinous processes of C7-T12
I: Lateral 1/3 of clavicle, acromion & spine of scapula
Trapezius innervation
Spinal portion of cranial nerve XI (accessory) and ventral ramus C2, 3, 4
Lat Dorsi action
1) Extend the shoulder
2) Adduct the shoulder
3) Medially rotate shoulder
Lat Dorsi O & I
O: Inferior angle of scap, T6-T12 spinous processes, thoracolumbar aponeurosis, posterior iliac crest
I: Intertubercular groove of humerus
Lat Dorsi innervation
Thoracodorsal nerve, C6, 7, 8
Teres major action
Same as lat dorsi - “lat’s little helper”
1) Extend shoulder
2) Adduct shoulder
3) Medially rotate shoulder
Teres major O & I
O: Inferior angle and lower 1/3 of lateral border of scapula
I: Crest of the lesser tubercle of the humerus
Teres major innervation
Lower subscapular nerve C5-C7 (but innervated by C6 branch)
