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Teres Major Muscle; Origin, Nerve Supply, Functions

Teres Major Muscle is a muscle of the upper limb. It attaches to the scapula and the humerus and is one of the seven scapulohumeral muscles. It is a thick but somewhat flattened muscle. The teres major muscle (from Latin teres, meaning “rounded”) is positioned above the latissimus dorsi muscle and assists in the extension and medial rotation of the humerus. This muscle is commonly confused as a rotator cuff muscle, but it is not because it does not attach to the capsule of the shoulder joint, unlike the teres minor muscle for example.

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.^[rx]

At a Glance of Teres major

Function: Adduction and medial rotation of the arm
Origin: Posterior surface of the scapula at its inferior angle
Insertion: Intertubercular groove on its medial aspect
Innervation: Lower scapular nerve (C5, C6)

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Details
Teres major muscle (in red) seen from the back (posterior to anterior perspective).
Origin	Posterior aspect of the inferior angle of the scapula
Insertion	The medial lip of the intertubercular sulcus of the humerus
Artery	Subscapular and circumflex scapular arteries
Nerve	Lower subscapular nerve (segmental levels C5 and C6)
Actions	adduct the humerus, Internal rotation (medial rotation) of the humerus, extend the humerus from flexed position, Depress shoulder
Identifiers
Latin	Musculus teres major
TA	A04.6.02.011
FMA	32549
*Anatomical terms of muscle*

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Nerve Supply of Teres Major Muscle

Teres major is supplied primarily by the lower subscapular nerve and additionally by the thoracodorsal nerve (middle subscapular nerve). These are distal to the upper subscapular nerve. These three nerves branch off the posterior cord of the brachial plexus. The nerves that innervate teres major consist of fibers from spinal nerves C5-C8.

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Functions of Teres Major Muscle

The teres major is a medial rotator and adductor of the humerus and assists the latissimus dorsi in drawing the previously raised humerus downwards and backward (extension, but not hyperextension). It also helps stabilize the humeral head in the glenoid cavity.