proc·to·de·um also proc·to·dae·um 
(prŏk′tə-dēəm)
(prŏk′tə-dēəm)n. pl. proc·to·de·a (-dēə) or proc·to·de·ums also proc·to·dae·a (-dēə) or proc·to·dae·ums
An inward fold on the surface of the embryonic ectoderm that develops into part of the anal passage.
[New Latin prōctodeum : Greek prōktos, anus + New Latin -odeum (probably from Greek hodaion, neuter of hodaios, on the way, from hodos, way).]