Overview
The cat has a slender, rod-shaped clavicle that does not articulate with the sternum or the scapula. It lies embedded in the muscle, cranial to the shoulder joint, and divides it into three parts. Classic feline anatomy texts use other names for them:
- Cleidobrachialis (m. cleidobrachialis): from the clavicle to the forearm. Clavodeltoid or clavobrachialis in feline texts.
- Cleidocervicalis (m. cleidocervicalis): from the clavicle to the dorsal neck and the nape. Clavotrapezius in feline texts.
- Cleidomastoideus (m. cleidomastoideus): from the clavicle to the mastoid process.
The last two make up the cleidocephalicus (m. cleidocephalicus), with its cervical and mastoid parts.
Origin and insertion
- The cleidocervicalis runs from the clavicle to the dorsal fibrous raphe of the cranial part of the neck and the nuchal crest of the occipital bone.
- The cleidomastoideus runs from the clavicle to the mastoid process of the temporal bone.
- The cleidobrachialis runs from the clavicle to the proximal end of the ulna, where its tendon joins that of the brachialis.
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. Puncture of the external jugular vein is a routine way to draw blood in the cat.
- It covers the superficial cervical lymph nodes.
- On radiographs the feline clavicle shows as a small bone cranial to the shoulder; it should not be mistaken for a fracture fragment or a foreign body.