Overview
Cattle have no clavicle. Instead, cranial to the shoulder joint, the muscle is crossed by a clavicular intersection (intersectio clavicularis), a tendinous sheet that divides it into two muscles:
- Cleidobrachialis (m. cleidobrachialis): from the clavicular intersection to the arm.
- Cleidocephalicus (m. cleidocephalicus): from the clavicular intersection to the head. In cattle it has two parts:
- Cleido-occipitalis (pars occipitalis): the dorsal part, towards the nape.
- Cleidomastoideus (pars mastoidea): the ventral part, towards the mastoid process.
Origin and insertion
- The cleidobrachialis runs from the clavicular intersection to the crest of the humerus, distal to the deltoid tuberosity, and to the brachial fascia.
- The cleido-occipitalis runs from the clavicular intersection to the funicular part of the nuchal ligament and the occipital bone.
- The cleidomastoideus runs from the clavicular intersection to the mastoid process of the temporal bone.
Action
The main muscle that advances the thoracic limb (shoulder extension). With the limb fixed, it draws the head and neck ventrally and laterally.
Innervation
Accessory nerve and ventral branches of the cervical nerves for the cleidocephalicus; axillary nerve for the cleidobrachialis.
Clinical relevance
- It forms the dorsal border of the jugular groove. The external jugular vein, in this groove, is the usual route for drawing blood and giving intravenous medication in cattle.
- Together with the omotransversarius it covers the superficial cervical (prescapular) lymph nodes, which are palpated cranial to the shoulder during the clinical examination.
- The side of the neck, cranial to the scapula, is the recommended injection site for intramuscular and subcutaneous injections in cattle. Beef Quality Assurance guidelines call for injecting here and not in the hindquarter, to avoid lesions in the most valuable cuts.