part of part of embryo cervical sinus of His http://upload.wikimedia.org/wikipedia/commons/2/20/Kiemenbogen.jpg sinus cervicalis EHDAA2:0000078 Wikipedia:Cervical_sinus RETIRED_EHDAA2:0000239 UBERON:0006216 cervical sinus it is ultimately obliterated by the fusion of its walls. A temporary depression caudal to the second pharyngeal arch, containing the succeeding pharyngeal arches; it is overgrown by the second pharyngeal arch and closes off as the cervical vesicle. This sinus is bounded in front by the hyoid arch, and behind by the thoracic wall. EMAPA:16884 sinus cervicalis EHDAA:6534 EHDAA:5105 retro-hyoid depression pharyngeal arch system pit