Glossary of Anatomy Muscles 450-475

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Teres Minor innervation
Axillary nerve
Supraspinatus origin and insertion
origin: Supraspinous fossa of scapula; insertion: Superior part of greater tubercle of humerus
Infraspinatus action
Helps to hold head of humerus in glenoid cavity; rotates humerus laterally
Infraspinatus innervation
Suprascapular nerve
Subscapularis origin and insertion
origin: Subscapular fossa of scapula; insertion: Lesser tubercle of humerus
Supraspinatus action
Stabilizes shoulder joint; helps to prevent downward dislocation of humerus, as when carrying a heavy suitcase; assists in abduction
Supraspinatus innervation
Suprascapular nerve
Deltoid origin and insertion
origin: Embraces insertion of the trapezius; lateral third of clavicle; acromion and spine of scapula; insertion: Deltoid tuberosity of humerus
Subscapularis action
Chief medial rotator of humerus; assisted by pectoralis major; helps to hold head of humerus in glenoid cavity, thereby stabilizing shoulder joint
Subscapularis innervation
Subscapular nerves (C5-C7)
Latissimus Dorsi origin and insertion
origin: Indirect attachment via lumbodorsal fascia into spines of lower six thoracic vertebrae, lower 3 to 4 ribs, and iliac crest; also from scapula’s inferior angle; insertion: Spirals around teres major to insert in floor of intertubercular groove of humerus
Deltoid action
Prime mover of arm abduction when all its fibers contract simultaneously; antagonist of pectoralis major and latissimus dorsi, which adduct the arm; if only anterior fibers are active, can act powerfully in flexion and medial rotation of humerus, therefore synergist of pectoralis major; if only posterior fibers are active, effects extension and lateral rotation of arm; active during rhythmic arm swinging movements during walking
Deltoid innervation
Axillary nerve (C5, C6)
Pectoralis major origin and insertion
Origin: Clavicle, sternum, cartilage of ribs 1-6, and aponeurosis of external oblique muscle; Fibers converge to insert by a short tendon into greater tubercle of humerus
Latissimus Dorsi action
Prime mover of arm extension; powerful arm adductor; medially rotates arm at shoulder; depresses scapula; because of its power in these movements, it plays an important role in bringing the arm down in a power stroke, as in striking a blow, hammering, swimming, and rowing
Latissimus Dorsi innervation
Thoracodorsal nerve
Pectoralis Major action
Prime mover of arm flexion; rotates arm medially; adducts arm against resistance; with scapula (and arm) fixed, pulls rib cage upward, thus can help in climbing, throwing, pushing and in forced inspiration

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