KIN 365 Applied Biomechanics 1 13 2016 Muscles can be named for their shape Deltoid muscle delta Rhomboid muscle rhombus Trapezius muscle trapezoid Muscles can also be named for the direction in which they run Rectus transverse abdominis straight across abdominals Origin where the muscle attaches Bi ceps two sites of origin triceps three sites of origin Planes of motion Frontal front and back Transverse top and bottom Joints Sagittal right and left All right angles 90 to each other All movement takes place at joints Muscles contract They cross joints if they didn t there would be no motion 1 15 2016 Joints Infraspinatus fossa shallow depression below the spine Look for name clues Synarthrodial joint immovable E g sutures Amphiarthrodial joint slightly moveable E g intervertebral discs Diarthrodial joint freely moveable E g hip shoulder knee elbow Muscle attaches to the bone via tendons Origin attachment site that doesn t move during contraction Insertion smaller attachment site that does move during contraction Movement of the scapula 1 Trapezius Origin base of skull occipital protuberance posterior ligaments of neck spinous processes of cervical C7 and all thoracic vertebrae T1 T12 Insertion posterior aspect of lateral third of clavicle medial border of acromion process and upper border of scapular spine triangular space at base of scapular spine Action Upper fibers elevation of scapula extension and rotation of head at the neck Middle fibers elevation upward rotation adduction retraction of the scapula Lower fibers depression adduction and upward rotation of scapula 2 Levator scapulae 3 Rhomboid Origin transverse processes of the upper four cervical vertebrae C1 4 Action elevates medial margin of scapula weak downward Insertion medial border of the scapula above the spine Origin spinous processes of last cervical C7 and first five thoracic vertebrae T1 5 Insertion medial border of scapula below spine Action Adduction draw scapula toward spinal column Downward rotation from upward rotated position draw scapula into downward rotation Elevation 4 Pectoralis minor Origin anterior surfaces of third to fifth ribs Action Insertion coracoid process of scapula Abduction protraction draws scapula forward and tends to tilt lower border away from ribs Downward rotation as it abducts it draws the scapula downward Depression assists when rotated upward 1 20 2016 Movement of the shoulder 1 Deltoid Origin anterior lateral third of clavicle lateral aspect of acromion inferior edge of spine of scapula Insertion deltoid tuberosity on the lateral humerus Action Anterior fibers abduction flexion horizontal adduction and internal rotation of the glenohumeral joint Middle fibers abduction of the glenohumeral joint Posterior fibers abduction extension horizontal abduction and external rotation of the glenohumeral joint 2 Pectoralis major Origin Upper fibers clavicular head medial half of the anterior surface of the clavicle Lower fibers sternal head anterior surfaces of costal cartilage of the first six ribs and adjacent portion of the sternum Insertion flat tendon 2 3 wide to the lateral lip of intertubercular groove of humerus Action Upper fibers clavicular head internal rotation horizontal adduction of humerus flexion up to about 60 abduction once the arm is abducted 90 the upper fibers assist in further abduction adduction w the arm below 90 of abduction of the glenohumeral joint Lower fibers sternal head internal rotation horizontal adduction adduction and extension of the glenohumeral joint from a flexed position to the anatomical position 3 Latissimus dorsi Origin posterior crest of ilium back of sacrum spinous processes of lumbar and lower six thoracic vertebrae slips from lower three ribs Insertion medial lip of intertubercular groove of humerus Action extension internal rotation adduction horizontal abduction o On posterior but wraps around front 1 22 2016 Movement of rotator cuff 1 Supraspinatus Origin medial two thirds of the supraspinatus fossa Action abduction of the glenohumeral joint stabilization of the humeral head in the Insertion superiorly on the greater tubercle of humerus glenoid fossa 2 Infraspinatus Origin medial aspect of the infraspinatus fossa just below the spine of the scapula posterior surface Insertion greater tubercle on posterior side Action external rotation of glenohumeral joint horizontal abduction of glenohumeral joint extension of glenohumeral joint stabilization of humeral head in the glenoid fossa 3 Teres minor Origin posteriorly on the upper and middle aspect of the lateral border of the scapula Insertion greater tubercle of humerus on posterior side o Supraspinatus infraspinatus and teres minor all posterior and all insert on greater tubercle Action external rotation of glenohumeral joint horizontal abduction of glenohumeral joint extension of glenohumeral joint stabilization of humeral head in glenoid fossa 4 Subscapularis Origin entire anterior surface of subscapular fossa Insertion lesser tubercle of humerus o On anterior surface not posterior like other three muscles of the rotator cuff o Inserts on LESSER tubercle instead of greater o Named for its origin Action internal rotation of glenohumeral joint adduction of glenohumeral joint extension of glenohumeral joint stabilization of humeral head in glenoid fossa Origin posteriorly on the inferior third of the lateral border of the scapula Action extension of glenohumeral joint particularly from flexed position to Insertion medial lip of the intertubercular groove of the humerus posteriorly extended position internal rotation of glenohumeral joint adduction of glenohumeral joint particularly from abducted position down to the side and toward the midline o Not a muscle of the rotator cuff 1 25 2016 1 Teres major Movement of the elbow 1 Biceps brachii Origin Long head supraglenoid tubercle Short head coracoid process Insertion tuberosity of the radius and bicipital aponeurosis lacertus fibrosis Action flexion of elbow supination of forearm weak flexion of the shoulder joint weak abduction of shoulder joint when shoulder joint is in external rotation o Two sites of origin biceps o Crosses two joints elbow and shoulder 2 Brachialis Origin distal half of the anterior shaft of the humerus Action true flexion of the elbow Insertion coronoid process of ulna 3 Brachioradialis Origin distal two thirds of lateral condyloid supracondylar ridge of humerus Action flexion of elbow protonation of forearm from supinated