Overview
Classic feline anatomy texts call it sternomastoid. The muscles of both sides arise together at the midline and diverge towards the head, forming a V on the ventral surface of the neck.
Origin
Manubrium of the sternum.
Insertion
Mastoid process of the temporal bone and nuchal crest of the occipital bone.
Action
Draws the head and neck ventrally or to the same side.
Innervation
Ventral branch of the accessory nerve (n. accessorius).
Clinical relevance
- It forms the ventral border of the jugular groove, used to locate and puncture the external jugular vein, a routine site for drawing blood in the cat.
- When examining a cat for suspected hyperthyroidism, the fingertips are slid along both sides of the trachea, from the larynx towards the thoracic inlet, to detect an enlarged thyroid lobe.