Insertions, Origins and Actions of Muscles

dellg85's version from 2016-01-29 00:10

Muscles of the shoulder joint

MuscleOriginInsertionJoint CrossedAction
Pectoralis MajorClavicle, sternum and the cartilage of ribs 1-6HumerusGlenohumeral (shoulder) jointShoulder horizontal flexion, shoulder adduction, shoulder medial rotation
Teres MajorLateral border of the scapula, near the inferior angleHumerus (proximal, anterior)Glenohumeral (shoulder) jointMedial rotation, adduction and extension of the shoulder joint
Latissimus DorsiVia the thoracolumbar fascia (TLF) from spinous processes of T6-T12, lumbar and sacral vertebrae and iliac crest. Also the lower 3-4 ribs and bottom (inferior) edge of the scapulaTop of the humerus (anterior)Glenohumeral (shoulder) jointOrigin fixed - adducts and extends the arm. Assists in medial rotation of the arm. Depresses the shoulder girdle via the insertion on the humerus. Insertion fixed - tilts the pelvis forwards
DeltoidClavicle (anterior head), acromion process of the scapula (medial head) and spine of the scapula (posterior head). Therefore, 3 attachments on 2 bonesLateral surface of the humerus (nearly halfway round)Glenohumeral (shoulder) jointAnterior fibres flex the shoulder and assist in horizontal flexion and medial rotation. All fibres abduct the shoulder (emphasis on the medial fibres though). Posterior fibres extend the shoulder and assist in lateral flexion and horizontal extension

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