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Skin anatomy

Epidermis

Adapted from Wikipedia · Discoverer experience

Illustration showing the layers of human skin, helping to understand how our body protects us.

The epidermis is the outer layer of the skin, which also includes the dermis and hypodermis. It acts as a important barrier that helps protect the body from infection caused by pathogens and controls how much water leaves the body into the atmosphere through a process called transepidermal water loss.

Made up of multiple layers of flattened cells, the epidermis grows from a base layer known as the stratum basale, which contains special columnar cells and stem cells. The thickness of the epidermis changes in different parts of the body, ranging from very thin to much thicker, but it generally becomes thinner as a person gets older. The epidermis is a type of tissue called a stratified squamous epithelium.

The term epidermis comes from Ancient Greek, where epi means 'over, upon' and derma means 'skin'. Anything related to the epidermis is described as epidermal.

Structure

Schematic image showing a section of epidermis, with epidermal layers labeled

The epidermis is the outer layer of skin and acts as a protective barrier. It is made up of several types of cells, including keratinocytes, which make up most of the cells, as well as melanocytes, Langerhans cells, and Merkel cells. These cells work together to protect the body from harmful substances and help control water loss.

The epidermis has several layers that change as cells move from the bottom layer to the top. Starting from the bottom, cells begin as basal cells and move upward, changing shape and function. By the time they reach the top layer, they become flat and filled with a special protein called keratin, which helps keep the skin strong and waterproof.

Function

The epidermis acts as a protective barrier for the body. It helps keep harmful germs and substances out while also protecting against small injuries. Special layers and cells in the epidermis work together to block unwanted materials and fight off infections.

The epidermis also helps keep the skin moist by controlling water loss. The color of our skin is mainly due to a substance called melanin, which is found in special cells called melanocytes. These cells give skin its color and change with sun exposure. The epidermis contains special touch-sensitive cells called Merkel cells, which help us feel when something touches our skin.

Clinical significance

For a comprehensive list, see List of cutaneous conditions.

Scientists often grow special skin cells in a lab to create artificial skin. This helps them test new medicines safely before using them on people.

Sometimes, the top layer of skin can become thicker. This can happen in different ways, such as in a condition called acanthosis, where the skin grows thicker overall. Another example is focal epithelial hyperplasia, which causes small, painless bumps inside the mouth. These changes are usually not serious and help doctors understand more about skin health.

Additional images

Epidermis and dermis of human skin

Cross-section of all skin layers

Illustration of epidermal layers

[Optical coherence tomography](/wiki/Optical_coherence_tomography) of fingertip

Images

A detailed diagram showing the layers and structure of human skin with clear labels.
A close-up microscopic view of the outer layer of human skin, called the stratum corneum.
A close-up microscopic view of the stratum granulosum layer of human skin, showing detailed cell structures.
A close-up microscopic view of skin layers, showing cells in the outer layer of the epidermis.
A close-up scientific image showing the base layer of human skin under a microscope.
A close-up photograph showing a skin condition called Acanthosis nigricans, which causes dark, thick patches on the skin.

This article is a child-friendly adaptation of the Wikipedia article on Epidermis, available under CC BY-SA 4.0.

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