The brachiocephalicus is a long and flat, complex of muscles that extends from the lower half of the humeral shaft to the head and neck. The muscle divides into two parts at the clavicular intersection. This is also the point of origin for all the muscles that make up the brachiocephalicus. This point is situated just cranial to the shoulder. The two main sections are the cleidobrachialis which is distal to the clavicular intersection and the cleidocephalicus which extends proximally to the clavivular intersection. The cleidocephalicus can also be divided into the pars cervicalis, which inserts on the broad aponeurosis, over the fibrous raphe of the cranial half of the neck. The other part, the pars mastoideus inserts on the mastoid process of the temporal bone via a strong tendon. The cleidobrachialis extends distally from the clavicular intersection and inserts on the cranial edge of the distal half of the humerus. The tendon that inserts the cleidobrachialis lies between the brachialis muscle and the biceps brachii. As a result of the brachiocephalicus spanning a large region it has the ability to provide a number of actions. These include extending the shoulder joint, protracts the limb, provides lateral movement of the head and allows the neck to be depressed. [ http://ccg.murdoch.edu.au/museum/ ]
Term information
The brachiocephalicus is more complex than other muscles of the forelimb. It consists of 2 elements that unite at the clavicle in dogs. In dogs the caudal part, known as the cleidobrachialis, runs from the clavicle to the humerus and is closely associated with the deltoid. The cranial portion runs from the clavicle to various attachments via a broad aponeurosis on the upper part of the head and neck. It is called the cleidomastoideus in the dog because it inserts on the mastoid process of the temporal bone. It may have a different name, like cleido-occipitalis, in other mammals. The name brachiocephalicus signifies that this complex of muscles runs from the upper arm to the head and does not specify the details of muscle attachments because these vary so much from species to species. The brachiocephalicus advances the limb and may also extend the shoulder joint, but this depends on the cranial attachment being fixed and the limb being free to move. However, when the forelimb is firmly on the ground and the head is free to move, it forces the head and neck either ventrally or to one side depending on whether or not both muscles act in tandem
Term relations
- skeletal muscle organ, vertebrate and attached to some humerus and attached to some mastoid process of temporal bone
- skeletal muscle organ, vertebrate
- muscle of shoulder
- attached to some humerus
- attached to some mastoid process of temporal bone