Anatomy of the Epidermis

The outermost layer of your skin

The epidermis is the uppermost layer of your skin. It is responsible for creating skin tone and protecting against toxins and infection.

Within the epidermis, there are four major layers of cells called keratinocytes that provide structural support for the skin. In addition to these four layers, you have another layer specific to your soles and palms.

This article describes the layers of cells in the epidermis, including their structure and function.

How Many Layers of Skin Are There?

There are three main layers. The epidermis sits above the dermis, the middle layer that contains connective tissue, hair follicles, and sweat glands that regulate the integrity and temperature of your skin. The deeper hypodermis layer, also called subcutaneous tissue, is made up of fat and even more connective tissue.

Stratum Basale

Straum basale

The bottom layer of the epidermis is called the stratum basale. This layer contains one row of column-shaped keratinocytes called basal cells.

Basal cells are constantly dividing and pushing already-formed cells towards the skin's surface. As basal cells move into the upper layer, they will also flatten, die, and be shed to make room for newer cells.

Melanocytes, the cells that produce melanin—the pigment which provides your skin its color—are also found in this layer.

Stratum Spinosum

Stratum spinosum

2007 Heather Brannon, MD licensed to About.com, Inc.

The spinosum layer lies just over the stratum basale and is only about five to 10 cells thick. In this layer, also known as the prickle cell or squamous cell layer, cells move in and change from column-shaped to multi-sided.

Cells in this layer are responsible for making keratin. This is the fibrous protein that gives skin, hair, and nails their hardness and water-resistant properties.

Stratum Granulosum

Stratum granulosum

The cells in the stratum granulosum, or granular layer, have lost their center (nuclei). This allows them to contain a high proportion of keratin to form the rigid cell layer of skin.

They appear as flattened cells containing dark clumps of cytoplasmic material, which are the parts of the cell minus the nucleus.

There is a lot of activity in this layer. Keratin proteins and lipids work together to create many of the cells responsible for the skin's protective barrier.

Stratum Lucidum

Stratum lucidum

The stratum lucidum layer is only present in the thicker skin of the palms and soles. Its main function is to reduce friction between the stratum corneum and stratum granulosum.

The name itself comes from the Latin for "clear layer," which describes the transparency of the cells themselves.

Stratum Corneum

Stratum corneum

The cells in the stratum corneum layer are known as corneocytes (or horny cells). These cells have flattened out and are considered dead.

Composed mainly of keratin proteins, corneocytes provide structural strength to the stratum corneum but also allow for the absorption of water. They serve as an effective barrier to any chemicals that might harm the living cells just beneath them.

Close-up of the stratum corneum

The structure of the stratum corneum may look simple, but it plays a key role in maintaining the structural integrity and hydration of the skin.

It ensures the continued production of new skin cells. It also provides vital protection against viruses, bacteria, parasites, and any other form of pathogen or toxin.

Summary

The epidermis is composed of layers of skin cells called keratinocytes. Your skin has four layers of skin cells in the epidermis and an additional fifth layer in areas of thick skin.

The four layers of cells, beginning at the bottom, are the stratum basale, stratum spinosum, stratum granulosum, and stratum corneum. In your palms and soles, there's an additional layer called stratum lucidum underneath the stratum corneum.

In the bottom layer, keratinocytes divide and push up formed cells toward the upper layer. The cells that reach the surface flatten and die. This provides a barrier to keep out pathogens and protect new skin cells underneath.

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5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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