Muscles of the Hip and Shoulder

Muscles that move the arm:

THE SCAPULAR MUSCLES

three sets of muscles connect upper humerus with scapula - all underneath spine of the scapula

INFRASPINATUS - larger and superior to teres minor

        and

TERES MINOR

origin - entire posterior surface of scapula starting at medial margin

insertion: back of the head of humerus

function: rotate arms outward (clockwise) - pulls against head of humerus

form: region over scapula bulges when flexed - fills in region under the spine of the scapula - creates a depression along the spine of the scapula

TERES MAJOR

 origin - inferior angle of scapula

 insertion - passes to front of humerus and inserts in bicipital groove

 function - rotates arm inward (counter-clockwise)

 form - same as teres minor

The muscles of the scapula all rotate the arm.

 

MUSCLE OF THE SHOULDER

DELTOID -

origin - like the trapezius it wraps from front to back of the trunk directly below insertion of trapezius on outer third to half of the clavicle origin - directly below insertion of trapezius on outer third to half of the clavicle - seems to continue the mass of the trapezius; continues around to the acromion process and the entire lower margin of the spine of the scapula


insertion - on lateral side of humerus about half way down (the deltoid impression)


action - to raise arms - not much leverage because the attachment is only halfway down the humerus


form - rounds shoulder somewhat - thickest mass is about center of the upper half of the humerus NOT at the head of the humerus

 

THE MUSCLES OF THE HIP

GLUTEUS MAXIMUS - one of the largest and strongest muscles in the body

origin: extends from the posterior quarter of the iliac crest and along the sacrum and coccyx

insertion: the deep fibers into the posterior surface of the shaft of the femur below the trochanters; the ilio-tibial band

action: extends thigh backward, adducts it, rotates it outward; provides tension for the ilio-tibial band; muscles of both sides press buttocks together

form: creates surface effect of sacral triangle (cause it to be a sunken shape); gluteal band of fascia creates gluteal fold — the fullness of the buttock is more a function of fat as the body stores fat in this area; when the gluteus maximus is contracted it becomes a "kidney bean" shape

 

GLUTEUS MEDIUS - above the great trochanter - triangular shape

origin: all along the iliac crest - partly overlapped in back by the gluteus maximus

insertion: great trochanter

form: fills out side of the hip

action: abducts thigh

 

TENSOR FASCIA LATAE (also FASCIA LATA)

origin: anterior superior iliac spine

insertion: ilio-tibial band, a band of fascia that stretches down the lateral side of the thigh

form: fills in depression between gluteus medius and upper quadriceps muscles

action: provides tension for ilio-tibial band and in doing so helps hold leg rigid; flexes and abducts thigh and rotates it inward

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