Teres minor muscle

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Teres minor muscle
Laterally rotates the arm, stabilizes humerus
Identifiers
Latinmusculus teres minor
TA98A04.6.02.010
TA22459
FMA32550
Anatomical terms of muscle]

The teres minor (Latin teres meaning 'rounded') is a narrow, elongated muscle of the rotator cuff. The muscle originates from the lateral border and adjacent posterior surface of the corresponding right or left scapula and inserts at both the greater tubercle of the humerus and the posterior surface of the joint capsule.[1]

The primary function of the teres minor is to modulate the action of the deltoid, preventing the humeral head from sliding upward as the arm is abducted. It also functions to rotate the humerus laterally. The teres minor is innervated by the axillary nerve.[2]

Structure

It arises from the dorsal surface of the axillary border of the

aponeurotic laminae, one of which separates it from the infraspinatus muscle, the other from the teres major muscle
.

Its fibers run obliquely upwards and laterally; the upper ones end in a tendon which is inserted into the lowest of the three impressions on the greater tubercle of the humerus; the lowest fibers are inserted directly into the humerus immediately below this impression.

Relations

The teres minor originates at the lateral border and adjacent posterior surface of the

shoulder-joint
.

Innervation

The muscle is innervated by the posterior branch of axillary nerve where it forms a

pseudoganglion.[3]
A pseudoganglion has no nerve cells but nerve fibres are present. Damage to the fibers innervating the teres minor is clinically significant.

Variation

Sometimes a group of muscle fibres from teres minor may be fused with

infraspinatus
.

Function

The

posterior deltoid
to externally (laterally) rotate the humerus, as well as adduction. Teres Minor can produce only very small scapular plane adduction during maximal contraction (Hughes RE, An KN 1996) with adductor moment arm of approximately 0.2 cm at 45° of shoulder internal rotation and approximately 0.1 cm at 45° of shoulder external rotation.

Clinical significance

Injury

There are two types of rotator cuff injuries: acute tears and chronic tears. Acute tears occur as a result of a sudden movement. This might include throwing a powerful pitch, holding a fast moving rope during water sports, falling over onto an outstretched hand at speed, or making a sudden thrust with the paddle in kayaking. A chronic tear develops over a period of time. They usually occur at or near the tendon, as a result of the tendon rubbing against the underlying bone.[4] The teres minor is typically normal following a rotator cuff tear.[5]

Imaging

Conjoint and intact tendon disc of teres minor and infraspinatus muscle.
Intact teres minor tendon with physiologically hypointense signal.
Hyperintense, fatty degenerated teres minor muscle.

shoulder dislocation, humeral neck fracture, brachial plexus
injury and thoracic outlet and inlet syndrome. It is important to include those pathologies for a complete as possible differential diagnosis.

MR angiography is required. The major task of an ultrasonographic examination is to rule out any space occupying mass. Additional electromyography is helpful to reveal any decelerated nerve conduction velocity, and thus denervation of the concerned muscle.[6]

Additional images

  • Position of the teres minor muscles (shown in red). Animation.
    Position of the teres minor muscles (shown in red). Animation.
  • Suprascapular and axillary nerves of right side, seen from behind. (Teres minor is visible at center.)
    Suprascapular and axillary nerves of right side, seen from behind. (Teres minor is visible at center.)
  • Diagram of the human shoulder joint, front view
    Diagram of the human shoulder joint, front view
  • Diagram of the human shoulder joint, back view
    Diagram of the human shoulder joint, back view
  • Left scapula. Dorsal surface.
    Left scapula. Dorsal surface.
  • Left humerus. Posterior view.
    Left humerus. Posterior view.
  • The scapular and circumflex arteries.
    The scapular and circumflex arteries.
  • The suprascapular, axillary, and radial nerves.
    The suprascapular, axillary, and radial nerves.
  • Teres minor muscle
    Teres minor muscle

See also

  • Accessory muscles of the scapula

References

Public domain This article incorporates text in the public domain from page 441 of the 20th edition of Gray's Anatomy (1918)

  1. ISBN 9780073403717
    .
  2. ISBN 9780073403717
    .
  3. PMID 13475146
    .
  4. ISBN 0-7360-4117-6
    .
  5. S2CID 8639793
    . Retrieved 28 November 2016.
  6. S2CID 6341877
    .

External links

Wikimedia Commons has media related to Teres minor muscles.
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