Question

Which one of the following is derived from ectoderm?
A. Enamel of teeth
B. Dentine
C. Skull
D. Axial skeleton

Answer 1

The ectoderm is a germ layer/tissue layer, which forms in an animal embryo during a period of development. By its name you can understand that the ectoderm is the germ layer that covers the portion outside of the embryo. The ectoderm then goes on to develop a number of both internal and external structures.

Complete answer:
You should know that it was believed that, like most of the vertebrate skeleton, the skull, vault and facial bones are derived from the mesodermal germ layer.
Whereas when we speak generally, the ectoderm differentiates to give rise to some types of epithelial tissues of the nervous system (like spinal cord, peripheral nerves and brain), tooth enamel and also the skin. Ectoderm makes the lining of the mouth, sweat glands, anus, nostrils, hair and nails. On the other hand, other types of epithelium are derived from the endoderm.
Remember, Teeth are formed from the mutual interaction of two germ layers as the ectoderm and ecto-mesenchyme (which is a neural crest derivative).
The ectodermal components give rise to the Enamel of teeth, whereas the dentine, pulp, cementum are all derived from -ectomesenchyme.

Therefore, the correct answer is option (A).

Additional information:
A germ layer is defined as a group of cells in an embryo which interact with each other as the embryo develops and helps in formation of all organs and tissues. Remember, all animals, except perhaps sponges, give rise to two or three germ layers. The germ layers are formed in early embryonic life, through the process of gastrulation.

Note: Keep in mind, the mesoderm develops the skeletal muscles, smooth muscle, blood vessels, bone, cartilage, kidney cortex, heart muscle, urogenital organ, joints, connective tissue, endocrine glands uterus, fallopian tube, testicles and blood cells by the spinal cord and lymphatic tissue.