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Infraspinatus muscle: Wikis

  

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Infraspinatus muscle
Arm muscles back numbers.png
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
Infraspinatus.PNG
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

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.

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.

See also

External links

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 As such, some of the information contained within it may be outdated.








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