Anatomy of the Shoulder Region and Back

Practice flashcards covering the vocabulary, origins, insertions, nerve supplies, and actions of the muscles of the shoulder region and back, including the rotator cuff and anatomical gateways.

Origin

The point of attachment of a muscle that remains relatively fixed during muscular contraction.

Insertion

The point of attachment of a muscle to the bone that it moves.

Deltoid Muscle

A muscle originating from the lateral third of the clavicle, acromion, and spine of scapula; it inserts into the middle of the lateral surface of the shaft of the humerus. It is supplied by the axillary nerve and acts to abduct the arm.

Supraspinatus

A muscle originating from the supraspinous fossa of the scapula and inserting into the greater tuberosity of the humerus and shoulder joint capsule. It is supplied by the suprascapular nerve and initiates abduction of the arm while stabilizing the shoulder joint.

Infraspinatus

A muscle originating from the infraspinous fossa of the scapula and inserting into the greater tuberosity of the humerus and shoulder joint capsule. It is supplied by the suprascapular nerve and acts to laterally rotate the arm and stabilize the shoulder joint.

Teres Major

A muscle originating from the lower third of the lateral border of the scapula and inserting into the medial lip of the bicipital groove of the humerus. It is supplied by the lower subscapular nerve and acts to medially rotate and adduct the arm.

Teres Minor

A muscle originating from the upper two thirds of the lateral border of the scapula and inserting into the greater tuberosity of the humerus and shoulder joint capsule. It is supplied by the axillary nerve and acts to laterally rotate the arm and stabilize the shoulder joint.

Subscapularis

A muscle originating from the subscapular fossa and inserting into the lesser tuberosity of the humerus. It is supplied by the upper and lower subscapular nerves and acts to medially rotate the arm and stabilize the shoulder joint.

Rotator Cuff

A functional group formed by the tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor which fuse to the shoulder joint capsule to provide stability.

Latissimus Dorsi

A large muscle originating from the iliac crest, lumbar fascia, spines of the lower $6$ thoracic vertebrae, lower $3$ or $4$ ribs, and inferior angle of the scapula. It inserts into the floor of the bicipital groove of the humerus and is supplied by the thoracodorsal nerve.

Trapezius

A muscle originating from the occipital bone, ligamentum nuchae, spine of the $7$th cervical vertebra, and all thoracic spines. Its upper fibers elevate the scapula, middle fibers pull it medially, and lower fibers pull the medial border downward. Motor supply is from the spinal part of the accessory nerve.

Rhomboid Major

A muscle originating from the $2$nd to $5$th thoracic spines and inserting into the medial border of the scapula; supplied by the dorsal scapular nerve to raise the medial border upward and medially.

Rhomboid Minor

A muscle originating from the ligamentum nuchae and spines of the $7$th cervical and $1$st thoracic vertebrae ($C7$ and $T1$); it inserts into the medial border of the scapula and is supplied by the dorsal scapular nerve.

Levator Scapulae

A muscle originating from the transverse processes of the $1$st four cervical vertebrae ($C1$-$C4$) and inserting into the medial border of the scapula; supplied by $C3$, $C4$, and the dorsal scapular nerve.

Suprascapular Foramen

A gateway formed by the suprascapular notch and the superior transverse scapular ligament; it transmits the suprascapular nerve, artery, and vein.

Quadrangular Space

A posterior gateway bounded by the inferior margin of the teres minor, surgical neck of the humerus, superior margin of the teres major, and lateral margin of the long head of triceps brachii. It contains the axillary nerve and posterior circumflex humeral artery and vein.

Triangular Space

An area of communication between the axilla and posterior scapular region bounded by the medial margin of the long head of triceps brachii, superior margin of teres major, and inferior margin of teres minor. It contains the circumflex scapular artery and vein.

Triangular Interval

A space formed by the lateral margin of the long head of triceps brachii, the shaft of the humerus, and the inferior margin of the teres major; it contains the radial nerve and the profunda brachii artery.