12. Shoulder Flashcards
Supraspinatus
Location
Origin
Insertion
Action
L- A rotator cuff muscle; named for its location on posterior aspect of scapula, deep to trapezius
O- Supraspinous fossa of scapula
I- Superior part of greater tubercle of humerus
A- Initiates abduction of arm; stabilizes shoulder joint; helps to prevent downward dislocation of humerus, as when carrying a heavy suitcase
Infraspinatus
Location
Origin
Insertion
Action
L - A rotator cuff muscle covered by deltoid and trapezius; named for its scapular location
O- infraspinous fossa of scapula
I - greater tubercle of humerus posterior to insertion of supraspinatus
A- laterally rotates arm; helps to hold of humerus in glenoid cavity, stabilizing the shoulder joint
Subscapularis
Location
Origin
Insertion
Action
L- A rotator cuff muscle; forms part of posterior wall of axilla; tendon of insertion passes in front of shoulder joint
O- subscapular fossa of scapula
I- lesser tubercle of humerus
A- Medically rotates arm; assisted pectoralis major; helps to hold head of humerus in glenoid cavity, stabilizing shoulder joint
Pectoralis major
Location
Origin
Insertion
Action
L- large, fan shaped muscle cover upper portion of chest; forms anterior axillary fold; divided into clavicular and sternal parts
O- sternal end of clavicle, sternum, cartilage of ribs and aponeurosis of external oblique muscle
I-fibers converge to insert by a short tendon into greater tubercle of humerus
A-Prime mover of arm flexion; rotates arm medially; adducts arm against resistance; w/scapula (and arm) fixed, pulls rib cage upward, and thus can help in climbing, throwing, pushing, and in forced inspiration
Deltoid
Location
Origin
Insertion
Action
L- Thick, multipennate muscle forming rounded shoulder muscle mass; a site commonly used for intramuscular injection, particularly in males, where it tends to be quite fleshy
O- lateral third of clavicle; acromion and spine of scapula
I- deltoid tuberosity of humerus
A- prime mover of arm abduction when all its fibers contract simultaneously. antagonist of pectoralis major and latissimus dorsi, which adduct the arm
Latissimus dorsi
Location
Origin
Insertion
Action
L-
Teres major
Location
Origin
Insertion
Action
L- Thick, rounded muscle; located inferior to teres minor, helps to form posterior wall of axilla (along w/latissimus dorsi and subscapularis)
O- posterior surfaces of scapula at inferior angle
I- crest of lesser tubercle on anterior humerus; insertion tendon fused w/that of latissimus dorsi
A- extends, medially rotates, and adducts the arm; synergist of latissimus dorsi
Teres minor
Location
Origin
Insertion
Action
L- A rotator cuff muscle; small, elongated muscle; lies inferior to infraspinatus and may be inseperable from that muscle
O- lateral border of scapula
I- greater tubercle of humerus inferior to infraspinatus insertion
A- Same actions as infraspinatus muscle
Coracobrachialis
Location
Origin
Insertion
Action
L- Small, cylindrical muscle; located in anterior compartment of arm
O- coracoid process of scapula
I-medial surface of humerus shaft
A- Flexion and adduction of arm; synergist of pectoralis major
