The sternocephalicus is a flat muscle and its caudal border is adjacent to the ventral border of the brachiocephalicus. The lateral aspect of this muscle is crossed obliquely by the external jugular vein. It originates as a unit on the first sternebrae. The cranial portion of the muscle divides into two separate sections with different insertion points. These are the sternomastoideus and the sterno-occipitalis. The ventral portion, the sternomastiodeus is the stronger and main continuation of the sternocephalicus, which inserts on the mastoid part of the temporal bone. The thin but wide dorsal segment, the sterno-occipitalis attaches to the dorsal nuchal crest by a thin aponeurosis. The main action provided by the sternocephalicus is movement of the head and neck to the side. Ventral branches of the cervical nerves are attached to this muscle. [ ]