Ectodermal appendage

Definition: 

A class of organs that all develop from the outer layer of the embryo, the ectoderm, through a series of coordinated and reciprocal interactions between the embryonic ectoderm and underlying dermal layer. This class of organs includes, sweat glands, hairs, mammary glands, teeth and nails. A largely shared set of genetic pathways initiate and control the development of this organ class.