<prompt> Which of the following structure develops from the proctodeum?RectumSigmoid colonUpper 23rd of anal canalLower 13rd of anal canal  <response>: Proctodeum or ectoderm lined anal pit is formed by the accumulation of mesodermal cells around the periphery of the anal membrane. This gives rise to lower 13rd of the anal canal. Cloaca is the terminal expanded poion of the primitive hindgut. The cloacal chamber is divided into dorsal and ventral cavities. The dorsal division gives rise to rectum and upper half of anal canal. The lower half of anal canal develops from proctodeum. Ref: Essentials Of Human Embryology Rev. Edn By Bhatnagar, S.M page 122 