Layers of Skin – A Very Brief, Introductory View

There are 3 main layers of skin:

  1. Epidermis (outermost layer)
  2. Dermis (middle layer)
  3. Hypodermis (fat layer)

Skin Biology - Layers of Skin

Epidermis – The Layer that COVERS

The epidermis is the outermost layer of skin. Its main job is to protect the body from the external environment and microorganisms.

It is further divided into 5 sub-layers:

  1. Stratum Corneum (Horny Layer)
  2. Stratum Lucidum (Clear Layer)
  3. Stratum Granulosum (Grainy Layer)
  4. Stratum Spinosum (Spiny Layer)
  5. Stratum Germinativum (Basal Layer)


The Stratum Corneum is the surface layer that you can see and feel. It is a layer of dead, hardened skin cells (corneocytes) made of a protein called keratin, the same protein in hair.

Inside the corneocytes is a collection of chemicals known as the Natural Moisturizing Factors (NMF’s) – free amino acids, lactic acid, urea, PCA, sugars, and inorganic salts. These chemicals keep the skin moist by attracting and holding onto water from the atmosphere.

Structure of the Epidermis

Dermis – The Layer that SUPPORTS

The dermis is the middle layer, beneath the epidermis. Its primary job is to provide structural support and moisture to the skin, and to connect the epidermis to blood vessels, lymph vessels, and nerves.

The dermis provides the scaffolding for the epidermis. Think of the epidermis as a mattress, and the dermis as the box springs. If the box springs (dermis) weaken, the mattress (epidermis) sags.

This scaffolding is called the Extracellular Matrix (ECM), an important support system for dermal cells. The matrix consists primarily of structural proteins (collagen and elastin) surrounded by a large amount of a ‘gel’ consisting of water, glycosaminoglycans, and proteoglycans. This gel-like fluid provides plumpness to the skin and is known as the Ground Substance.

The dermis is divided into 2 sub-layers:

  1. Papillary Dermis (upper part of dermis)
  2. Reticular Dermis (lower part of dermis, the bulk of the dermis)

The Papillary Dermis contains blood vessels (capillaries) that provide oxygen and nutrients to skin cells in the epidermis and lymph vessels that carry away waste from the epidermis. It also contains nerves and elastic fibers (which is why sagging primarily occurs here).

The Reticular Dermis contains dense collagen and elastin fibers, hair follicles, sebaceous glands, sweat glands, and larger blood vessels. There is a lot more collagen than elastin, so this is the area where wrinkles form.

The dermis also contains immune cells as well as fibroblasts, which are specialized cells that make collagen, elastin, glycosaminoglycans, and proteoglycans.

Between the epidermis and dermis lies a thin area called the Dermal-Epidermal Junction. It is also known as the Basement Membrane (Rete Pegs). The rete pegs look like ridges. As the skin ages over time, these ridges flatten out and the junction gets thinner. This flattening of the rete pegs is a major site of aging in the skin.

Hypodermis – The Layer that CUSHIONS

The hypodermis is the subcutaneous fat layer. It is about 80% fat. Its main job is to cushion the body from impact and store energy.

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