Question Detail

The ectoderm is the outermost germ layer. It gives rise to the nervous system (brain, spinal cord), the epidermis of the skin (including hair and nails), and the linings of the mouth and nostrils (epithelial parts). The nostrils themselves are openings, but the lining of the nostrils is ectodermal. This is tricky. Perhaps the question means the actual structure of the nostrils is not solely ectodermal. All options are ectodermal derivatives, so E (none) might be correct. However, 'nostrils' as a whole structure might be considered not purely ectodermal. Given common exam questions, the nervous system and skin derivatives are classic ectoderm, and nostrils are often grouped with mouth lining as ectoderm. I'll go with E as the safest.