Infraspinatus muscle
Muscles on the dorsum of the scapula, and the Triceps brachii muscle: #3 is Latissimus dorsi muscle #5 is Teres major muscle #6 is Teres minor muscle #7 is Supraspinatus muscle #8 is Infraspinatus muscle #13 is long head of Triceps brachii muscle
Muscles connecting the upper extremity to the vertebral column.
Latin	musculus infraspinatus
Gray's	subject #123 441
Origin	infraspinous fossa of the scapula
Insertion	middle facet of greater tubercle of the humerus
Artery	suprascapular and circumflex scapular arteries
Nerve	suprascapular nerve
Actions	Lateral rotation of arm and stabilizes humerus

The Infraspinatus muscle is a thick triangular muscle, which occupies the chief part of the infraspinatous fossa. The infraspinatus is a muscle of the rotator cuff, and is innervated by the suprascapular nerve.

Contents 1 Origin and insertion 2 Relations 3 Action 4 See also 5 External links

[edit] Origin and insertion

It attaches medially to the infraspinous fossa of the scapula and laterally to the greater tubercle of the humerus.

It arises by fleshy fibers from its medial two-thirds, and by tendinous fibers from the ridges on its surface; it also arises from the infraspinatous fascia which covers it, and separates it from the Teres major and Teres minor.

The fibers converge to a tendon, which glides over the lateral border of the spine of the scapula, and, passing across the posterior part of the capsule of the shoulder-joint, is inserted into the middle impression on the greater tubercle of the humerus.

[edit] Relations

The tendon of this muscle is sometimes separated from the capsule of the shoulder-joint by a bursa, which may communicate with the joint cavity.

[edit] Action

It is an external rotator of the glenohumeral joint and adductor of the arm.

The Infraspinatus and Teres minor rotate the head of the humerus outward (external rotation); they also assist in carrying the arm backward. Studies by Lastayo, w., etc. have shown the infraspinatus to be the major external rotator of the shoulder in comparison with the teres minor.^{[citation needed]}

[edit] See also

• Rotator cuff

[edit] External links

• LUC infs
• SUNY Figs 03:03-04
• infraspinatus+muscle at eMedicine Dictionary

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.

v • d • e List of muscles of upper limbs (TA A04.6, GA 4.432) Shoulder deltoid · rotator cuff (supraspinatus, infraspinatus, teres minor, subscapularis) · teres major fascia: Deltoid fascia · Supraspinous fascia · Infraspinous fascia Arm (compartments) Anterior coracobrachialis · biceps brachii · brachialis Posterior triceps brachii · anconeus · Articularis cubiti Fascia Axillary sheath · Axillary fascia · Brachial fascia · intermuscular septa (Lateral, Medial) Other spaces (Quadrangular space, Triangular space, Triangular interval) Forearm Anterior superficial: pronator teres · palmaris longus · flexor carpi radialis · flexor carpi ulnaris · flexor digitorum superficialis deep: pronator quadratus · flexor digitorum profundus · flexor pollicis longus Posterior superficial: mobile wad (brachioradialis, extensor carpi radialis longus and brevis) · extensor digitorum · extensor digiti minimi · extensor carpi ulnaris deep: supinator · anatomical snuff box (abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus) · extensor indicis Fascia Bicipital aponeurosis · common tendons (Extensor, Flexor) · Antebrachial fascia Other Cubital tunnel Hand Lateral volar thenar (opponens pollicis, flexor pollicis brevis, abductor pollicis brevis) · adductor pollicis Medial volar hypothenar (opponens digiti minimi, flexor digiti minimi brevis, abductor minimi digiti) · palmaris brevis Intermediate lumbrical · interossei (dorsal, palmar) Fascia posterior: Extensor retinaculum · Extensor expansion anterior: Flexor retinaculum · Palmar aponeurosis

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