Question

Ectoderm produces:
A. Mesodaeum
B. Proctodaeum
C. Stomodaeum
D. Both B and C

Answer 1

Hint: The ectoderm is a germ layer, or tissue layer, that structures in an organism during development. As the name recommends, the ectoderm is the germ layer that covers the outside of the embryo ('ecto' which means outside). The ectoderm then goes on to give rise to both internal and external structures.

Complete Answer:
- The ectoderm is one of the two tissue layers present in diploblasts, alongside the endoderm, and one of the three layers found in triploblasts, alongside the endoderm and mesoderm. The ectoderm structures during gastrulation, the cycle in embryogenesis where cells modify and begin differentiation.
- A proctodaeum is the back ectodermal part of the alimentary canal. It is formed during embryogenesis by a folding of the outer body wall. It will shape the lower part of the anal-canal, underneath the pectinate line, which will be lined by stratified squamous non-keratinized (zona hemorrhagica) and stratified squamous keratinized (zona cutanea) epithelium.
- The stomodeum, additionally called stomodeum or stomodaeum, is a depression between the brain and the pericardium in an embryo, and is the precursor of the mouth and the anterior lobe of the pituitary gland. The stomodeum is lined by ectoderm, and is isolated from the anterior end of the front gut by the buccopharyngeal membrane.
- Both Proctodaeum and Stomodaeum are created during embryogenesis which is framed by ectoderm.

Hence, the right answer is D, i.e. Both B and C.

Note: The ectoderm cells differentiate into cells that structure various external structures, for example, skin, sweat organs, skin sensory receptors, and hair follicles. Likewise, the ectoderm shapes the external surfaces of the eyes (cornea and lens), teeth (enamel), mouth, and rectum, just as the pineal and pituitary glands.