Shoulder Girdle Muscles Flashcards
Supraspinatus
Posterior
Origin: supraspinous fascia, supraspinous fossa
Insertion: greater tubercle of humerus
Action: holds humerus in socket, tenses capsule, abducts arm
Infraspinatus
Posterior
Origin: infraspinous fossa, spine of scapula, infrapinous fascia
Insertion: greater tubercle of humerus
Action: external rotation of arm
Teres Minor
Posterior
Origin: lateral border of scapula
Insertion: lower facet of greater tubercle of humerus
Action: weak external rotator of arm
Deltoid
Posterior, 3 parts
Clavicular origin: lateral third of clavicle
Acromial origin: acromion process of scapula
Spinal origin: inferior border of scapular spine
Insertion: all attached to deltoid tuberosity
Action: principal abductor of shoulder
Subscapularis
Posterior
Origin: subscapular fossa
Insertion: lesser tubercle of humerus, proximal part of crest
Action: internal rotation of arm
Teres Major
Posterior
Origin: lateral border of scapula near inferior angle
Insertion: Lesser tubercle of humerus
Action: retroversion of arm towards midline, little medial rotation, helps in adduction
Lattimus Dorsi
Posterior
Origin: spinous process of 7th- 12th thoracic vertebra
Insertion: lesser tubercle of humerus
Action: lowers raised arm, adducts it, when adducted… pulls it backward and medially, pulls shoulders backward and downward, works during forced expiration
Coracobrachialis
Anterior
Origin: coracoid process
Insertion: medial surface of humerus, in line with crest of lesser tubercle
Action: anteverts arm and retains humeral head in articular facet
Pectoralis Minor
Anterior
Origin: 3rd to 5th ribs
Insertion: coracoid process of scapula
Action: lowers and rotates the scapula
Pectoralis Major
Anterior
Clavicular origin: medial half of anterior surface of clavicle
Sternocostal origin: sternal membrane and cartilages of 2nd to 6th ribs
Abdominal origin: anterior layer of uppermost part of rectus sheath (lower abdominal sheath)
Insertion: crest of greater tubercle of humerus
Action: when arm is adducted…. clavicular and sternal parts produce ante version, all parts work to lower the raised arm, adduct arm and rotate it medially
sternocostal and abdominal part work to lower shoulder anteriorly
accessory muscle for inspiration when arms are fixed (helps move thorax)
Rhomboid Minor
Posterior
Origin: spinous process of 6th to 7th cervical vertebrae
Insertion: medial border of scapula
Action: press scapula against chest wall and retract scapula toward vertebral column (like rhomboid major)
Rhomboid Major
Posterior, caudal then minor is up
Origin: spinous process of 1st-4th thoracic vertebrae
Insertion: medial border of scapula, caudal to rhomboid minor
Action: ction: press scapula against chest wall and retract scapula toward vertebral column (like rhomboid minor)
Levator Scapulae
Posterior
Origin: posterior tubercles of transverse processes of 1st to 4th cervical vertebrae
Insertion: superior angle of scapula and adjacent part of medial border
Action: elevates scapula while rotating the inferior angle medially
Serratus Anterior
Posterior
Origin: surface of 1st to 9th ribs
Insertion:
Superior origin: superior angle of scapula
Intermediate part: medial border of scapula
Inferior part: attached near inferior angle of scapula
Action: pulls scapula anteriorly (essential for anteverting arm), superior and inferior parts press scapula into thorax, inferior part rotates scapula laterally and pulls the inferior angle and lateral forward for elevation of the arm, all parts work together to lift ribs when shoulder girdle is fixed
Subclavius
Anterior
Origin: osteochondral junction of 1st rib
Insertion: subclavian groove on inferior surface of clavicle
Action: pulls clavicle toward sternum, stabilizes sternoclavicular joint