Understanding Skin Layers

In thisarticle, we discuss some of the functions of the skin's layers. Once you understand how the different layers of the skin work, you can determine how to treat the skin conditions related to each layer, particularly those related to wrinkles and aging.

Stratum Corneum

The stratum corneum is the outermost layer of skin, the last of the epidermal layers. This layer of skin is made up of dead, smooth skin cells that shed approximately every couple of weeks and are then renewed. The main function of the stratum corneum is to work as the skin's outer barrier, keeping water out and shaping the appearance of the skin by adding strength and elasticity. This layer is strong, able to absorb and release energy, and elastic, so it can hold its shape and resist any forced change.

The stratum corneum is made up of a keratin protein filament network and lipids, forming five connected layers that interact with one another. When this functional network is disrupted, as happens when we age, we see an increase in dry skin, atopic dermatitis, psoriasis, or other skin conditions.

Epidermis

The epidermis is the most superficial of the skin's layers. It is composed of the five layers, including the stratum corneum. The bottom, or basal layer, produces the keratin by which dead skin cells are replaced on the upper layers. It takes two weeks for the new cells to move to the top layer of skin. Melanin is found in the basal epidermal layer.

The second layer is the stratum spinosum or the prickly layer. It is held together by prickly cells and is where protein (keratin) is synthesized. The next layer is the granular layer where melanocytes, precursors to keratin, are found. The stratum lucidum is the fourth layer, which is very thin. It is found almost exclusively in the palms of the hand and soles of the feet.

Dermis

The dermis is the skin that lies below the epidermal layers. It is comprised of two layers: the papillary and the reticular layers. The papillary layer is composed of connective tissue, collagen, and elastin. The reticular layer contains thick connective tissue and collagen fibers. Collagen fibers are very strong and give the skin its durability and toughness. Elastin fibers keep the skin flexible and pliable. The dermis also contains hair follicles, sweat and sebaceous glands, blood vessels and fibroblasts. Fibroblasts are an integral part of the skin's structure. They produce collagen and deposit it where it is needed for growth and additional strength in the dermis. Loss of dermis can cause the epidermis to atrophy, leaving the skin thinner and more wrinkled.

Subcutaneous Tissue

Hypodermis The subcutaneous layer is located just below the dermis. It is a layer of fat also known as subcutaneous tissue or the hypodermis. It is made up of loose connective and adipose tissue. The hypodermis aids in metabolism and insulates the skin. Inflammation in the hypodermis can cause skin dimpling or cellulitis.