Glossary
epidermis
The epidermis is the outer, avascular layer of the skin — stratified epithelium that renews from its base and makes keratin and melanin.
The epidermis is the skin's outer layer, a sheet of stratified epithelial tissue with no blood vessels in it. It is fed by diffusion from the dermis below, which is why a shallow scrape does not bleed and a deep one does. Cells are made at the base, pushed outward as newer cells form beneath them, and flattened and filled with keratin by the time they reach the surface, where they are shed. Keratin is what makes the surface waterproof and resistant to abrasion. Melanocytes at the base add melanin, which colors the skin and absorbs ultraviolet light. Because the epidermis renews itself completely, a superficial burn heals without a scar; a burn deep enough to destroy the base does not. Thick skin on the palms and soles carries an extra layer and no hair follicles.
Taught in
Related terms
- dermis — The dermis is the layer under the epidermis: connective tissue carrying the blood vessels, nerves, glands and hair follicles the skin needs.
- hypodermis — The hypodermis is the fatty layer under the dermis — subcutaneous tissue that insulates, cushions, stores energy and anchors the skin.
- epithelial tissue — Epithelial tissue covers and lines surfaces, forms glands, and sits on a basement membrane — it has no blood vessels of its own.
Source: The anatomy and physiology guide in this course, whose organ and tissue descriptions follow the US National Cancer Institute's SEER Training Modules and MedlinePlus consumer health pages. Both are US federal government material, not subject to copyright in the United States. The definition above is written for this course in our own words. (SEER Training Modules accessed 2026-10-26; definition written 2026-10-27)