chorioallantois: the very vascular fetal membrane composed of the fused chorion and adjacent wall of the allantois
membrane: a pliable sheet of tissue that covers or lines or connects the organs or cells of animals or plants
meningocele: a congenital anomaly of the central nervous system in which a sac protruding from the brain or the spinal meninges contains cerebrospinal fluid (but no nerve tissue)