Which layer eventually forms hair, nails, and tooth enamel?

The layer that eventually forms hair, nails, and tooth enamel is the ectoderm. The ectoderm is one of the three primary germ layers formed during the embryo's development. It gives rise to structures that are involved in the body's outer covering and interactions with the environment.

As development progresses, the ectoderm differentiates into various tissues. For example, it produces the epidermis, which is the outer layer of the skin, as well as appendages associated with the skin, such as hair and nails. Additionally, the ectoderm contributes to the formation of the enamel of teeth, which is the hard, protective outer layer.

In contrast, the mesoderm primarily gives rise to structures such as muscles, bones, and the circulatory system, while the endoderm leads to the formation of internal structures like the gastrointestinal tract and associated organs. The trophoblast, on the other hand, is involved in the implantation of the embryo into the uterine wall and eventually contributes to the placenta, rather than directly forming the aforementioned structures.