Cervical sinus

During Human embryogenesis the mandibular arch and hyoid arch grow more rapidly than those behind them, with the result that the latter become, to a certain extent, telescoped within the former, and a deep depression, the cervical sinus, is formed on either side of the neck.

This sinus is bounded in front by the hyoid arch, and behind by the thoracic wall; it is ultimately obliterated by the fusion of its walls.

Formed by the walls of the 2-4th pharyngeal grooves merging. Sometimes it can remain anterior to the sternocleidomastoid muscle. It can communicate with the skin( external cervical fistula) or with the pharynx ( internal cervical fistuala). Prone to infection.