Overview
It has four heads ending on the olecranon: long, lateral, medial and accessory. The model shows the first three; the accessory head is deep and hidden between them.
In the cat, the epitrochlearis (m. tensor fasciae antebrachii, called epitrochlearis or dorsoepitrochlearis in feline texts) runs over the medial surface of the long head: a sheet that leaves the latissimus dorsi and ends on the olecranon and the antebrachial fascia.
Origin
- Long head (caput longum): caudal border of the scapula. The only head that crosses the shoulder.
- Lateral head (caput laterale): tricipital line on the lateral surface of the proximal humerus.
- Medial head (caput mediale): medial surface of the humerus.
Insertion
Olecranon tuber (tuber olecrani) of the ulna.
Action
Extends the elbow and supports body weight when standing. The long head also flexes the shoulder.
Innervation
Radial nerve (n. radialis).
Clinical relevance
Brachial plexus avulsion after road accidents is common in the cat. When it involves the caudal roots (C7–T1), which form the radial nerve, the cat cannot extend the elbow or bear weight on the limb, and knuckles over onto the dorsum of the paw.