The cervical sinus is a structure formed during embryonic development.

It may fail to obliterate, forming a branchial cleft cyst or fistula, which is prone to infection.

It is ultimately obliterated by the fusion of its walls by the 7th week of gestation.

Sometimes, the cervical sinus can fail to obliterate and thus remains as a branchial cleft cyst.

[1] This article incorporates text in the public domain from page 67 of the 20th edition of Gray's Anatomy (1918) This developmental biology article is a stub.