Overview
The humerus (humerus) forms the skeleton of the arm. It runs obliquely in a caudoventral direction from the shoulder to the elbow and is almost entirely covered by muscles. In cattle it is relatively short and sturdy. The greater tubercle forms the point of the shoulder, palpable in the live animal.
Proximal end
- Head (caput humeri): caudal, articulates with the glenoid cavity of the scapula.
- Greater tubercle (tuberculum majus): lateral and very large; it is divided into a cranial part, which rises above the head, and a caudal part. Insertion of the supraspinatus and infraspinatus muscles.
- Lesser tubercle (tuberculum minus): medial; insertion of the subscapularis.
- Intertubercular groove (sulcus intertubercularis): a single groove between the two tubercles through which the tendon of the biceps brachii runs. Cattle lack the intermediate tubercle of the horse.
Shaft
- Deltoid tuberosity (tuberositas deltoidea): on the lateral surface; insertion of the deltoideus.
- Teres major tuberosity: on the medial surface; insertion of the teres major and latissimus dorsi muscles.
- Brachial groove: spiral groove on the lateral surface that holds the brachialis muscle and the radial nerve.
Distal end
- Humeral condyle (condylus humeri): articular surface for the radius and ulna at the elbow joint.
- Medial and lateral epicondyles: origin of the flexor and extensor muscles of the carpus and digits.
- Olecranon fossa: deep, on the caudal surface; receives the anconeal process of the ulna when the elbow extends. There is no supratrochlear foramen, a feature of the dog.
Clinical relevance
- Fractures: uncommon; they mainly affect young animals after trauma. The large muscle mass makes it impossible to immobilise the humerus with a cast.
- Radial nerve paralysis: the nerve can be injured in humeral fractures or by compression during prolonged lateral recumbency (downer cows, surgery); the animal cannot extend the elbow, carpus or digits, stands with a dropped elbow and drags the dorsal surface of the hoof.