Infraspinatus muscle

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.

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 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.

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.

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]}

See also

• Rotator cuff

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 As such, some of the information contained herein may be outdated.

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