Attachment points of the teres minor muscle
The teres minor muscle (m. teres minor) has clearly defined points of origin and insertion that determine its biomechanical role in the shoulder joint:
- Origin (Origo): muscle fibers originate from the lateral border of the scapula.
- Insertion (Insertio): fibers course laterally and attach to the lower facet of the greater tubercle of the humerus (tuberculum majus humeri).
Function, innervation, and blood supply
Understanding the muscle's function requires knowledge of its neurovascular supply.
Function (Actio): The main task of this muscle is lateral rotation of the arm (supination). In addition, during joint movements, it retracts the capsule of the shoulder joint, preventing its impingement between the articular surfaces.
Innervation (Nervus): Motor impulses are supplied by the axillary nerve — n. axillaris. This nerve originates from the C₅–C₆ spinal roots.
Blood supply (Vasa): Trophics of the muscle tissue are provided by the circumflex scapular artery (a. circumflexa scapulae).
It is also worth noting an important topographical feature: between the muscle itself and the capsule of the shoulder joint lies the subtendinous bursa of the teres minor muscle — bursa subtendinea m. teretis minoris, which reduces friction during contraction.
Flexor carpi ulnaris (additional)
As part of studying the muscular apparatus of the upper extremity, the flexor carpi ulnaris (m. flexor carpi ulnaris) is also distinguished.
Attachment points:
- Origin: the muscle has two heads. The humeral head (caput humerale) originates from the medial epicondyle, and the ulnar head (caput ulnare) — from the olecranon.
- Insertion: the tendon attaches to the pisiform bone (os pisiforme), hook of the hamate (hamatum), and the base of the 5th metacarpal bone.
Biomechanics and blood supply: The muscle performs flexion of the wrist and its adduction in the ulnar direction. Blood supply is provided by the ulnar artery (a. ulnaris), as well as the superior and inferior ulnar collateral arteries (a. collateralis ulnaris superior et inferior). Innervation is provided by the ulnar nerve — n. ulnaris (C₇–C₈).
Briefly: answers to topical questions
Where does the teres major muscle originate?
The teres major muscle (m. teres major) originates from several structures of the scapula.
- Angle of the scapula (angulus scapulae) — specifically, from its inferior angle.
- Lateral border of the scapula (margo lateralis) — from the lower half of this border.
- Infraspinous fascia (fascia infraspinata) — from the outer surface of this fascia.
Where does the teres major muscle insert?
The teres major muscle (m. teres major) inserts into the proximal part of the humerus.
- Crest of the lesser tubercle (crista tuberculi minoris humeri) — a bony ridge that extends inferiorly from the lesser tubercle of the humerus.
In the area of insertion, between the tendon of the muscle and the latissimus dorsi, there is a bursa (bursa subtendinea m. teretis majoris).
What are the functions of the teres major muscle?
The teres major muscle performs several motor functions regarding the arm.
- Adduction of the arm — pulls the upper extremity toward the torso.
- Extension of the arm — moves the arm from front to back.
- Medial rotation of the arm — rotates the humerus medially.
- Lowering of the raised arm — returns the extremity to its original position.
What is the innervation of the teres major muscle?
The teres major muscle (m. teres major) is innervated by:
- Subscapular nerve (n. subscapularis) — C₆–C₇.
Sources also indicate that the teres major muscle belongs to the group of muscles innervated by the thoracodorsal nerve (C₅–C₈, from the posterior cord of the brachial plexus).
Which muscles of the shoulder girdle laterally rotate the arm?
Lateral rotation of the arm is performed by several muscles of the shoulder girdle.
- Teres minor muscle (m. teres minor) — additionally retracts the joint capsule.
- Infraspinatus muscle (m. infraspinatus) — also pulls the joint capsule, preventing its impingement.
- Supraspinatus muscle (m. supraspinatus) — in addition to lateral rotation, participates in arm elevation.
Class and exam questions
Where does the teres minor muscle originate?
The muscle originates from the lateral border of the scapula.
Which artery supplies m. teres minor?
Blood supply is provided by the circumflex scapular artery (a. circumflexa scapulae).
What is the function of the flexor carpi ulnaris?
It performs flexion of the wrist and also adducts it in the ulnar direction.
What else to study on this topic
- Anatomy of the teres major muscle (not included in the provided data)
- Deep (III) muscle layer
- Topography of the axillary nerve (n. axillaris)
- Synovial bursae of the shoulder joint
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