| Term | Definition |
| epithelium | cells covering external and internal surface |
| epidermis | thin, cellular outer layer of the skin |
| squamous cell layer | flat, scale-like epithelial cells comprising the outermost layers of the epidermis |
| basal layer | deepest region of the epidermis |
| melanocyte | a cell found in the basal layer that gives color to the skin |
| melanin | dark brown to black pigment contained in melanocytes |
| dermis | densse, fibrous connective tissue layer of the skin (corium) |
| sebaceous glands | oil glands in the skin |
| sebum | oily substance secreted by the sebaceous glands |
| sudoriferous glands | sweat glands |
| subcutaneous tissue | connective and adipose tissue layer just under the dermis |
| collagen | protein substance found in skin and connective tissue |
| hair | outgrowth of the skin composed of keratin |
| nail | outgrowth of the skin attached to the distal end of each finer and toe, composed of keratin |
| keratin | hard protein material found in the epidermis, hair, and nails |