Question

The proctodaeum develops from
A. Ectoderm
B. Mesoderm
C. Endoderm
D. None of the above

Answer 1

Hint: A proctodeum is made by the folding of an outer body wall. It plays an important role in the absorption of electrolytes and passive absorption of the fluids.

Complete Answer:
- A proctodeum is the back ectodermal aspect of a digestive tract. It is made during embryogenesis by a collapsing of the outer body wall. It will frame the lower part of the anal trench, beneath the pectinate line, which will be lined by stratified squamous non-keratinized (zonahemorrhagica) and stratified squamous keratinized (zona cutanea) epithelium. The intersection between them is Hilton’s white line.
- The gastrointestinal tract emerges by the start of the third seven day stretch of embryonic development events. During a cycle called gastrulation, the three germ layers structure. The germ layers incorporate the ectoderm, mesoderm, and endoderm, which together create the early stage plate.
- During the fourth week, the early stage gastrointestinal tract starts to frame from the endoderm. As the embryo folds towards the midline, the endoderm makes a gut tube that is suspended by mesentery, or two fold layers of peritoneum. The gut tube separates into the foregut, midgut, and hindgut. The terminal finish of the hindgut incorporates the cloaca, which structures the gastrointestinal tract as well as the urogenital tract.
- Towards the caudal finish of the cloaca is an area called the cloacal membrane, which is a limit between the endoderm layer and the ectoderm layer with no mesoderm in the middle of; this at last structures the proctodeum.

So, the correct answer is option A. Ectoderm.

Note: The inner cell mass of the blastocyst after implantation separates into an external ectoderm, centre mesoderm and inward endoderm. These layers at that point form into tissues and organs of the undeveloped organism i.e. embryo. A proctodeum is the back ectodermal aspect of an alimentary canal.