The hair, nails, oil glands, and sweat glands are called epidermal derivatives. This means that they are structures that developed from the embryonic epidermis during prenatal development. Although they are considered to be epidermal structures, some of them are located deep in the dermal layer. Eyelashes and eyebrows shield the eyes from sunlight and dust. Nose hairs keep dust and foreign particles out of the respiratory tract.
Hair is distributed on nearly all parts of the body.
They are absent from the palms of the hands, soles of the feet, lips, nipples, and portions of the external genitalia. Normal hair loss in an adult scalp is about 70-100 hairs a day. The hair consists of dead, keratinized epithelial cells. The cuticle is formed from a single layer of flat cells that overlap one another like shingles on a roof. The cuticle is the most heavily keratinized layer of cells in the hair, so it provides strength to the hair.