Chapter 21: Integumentary System

Skin The skin is the largest organ in the body and has a dual origin: (1) A superficial layer, the epidermis, develops from the surface ectoderm. (2) A deep layer, the dermis, develops from the underlying mesenchyme. Epidermis Initially, the embryo is covered by a single layer of ectodermal cells (Fig. 21.1A). In the beginning […]