The Structure of Skin

The importance of keeping your skin healthy can't be overemphasized. It's the body's first defense against disease and infection, and it protects your internal organs from injuries. It is, in fact, the largest organ in the body. The skin helps regulate body temperature and prevents excess fluid loss, and it also helps your body remove excess water and salt.

Skin conditions can affect anyone—young and old, men and women. Acne, psoriasis and eczema are just a few examples of common skin disorders. The good news is that there are a number of simple ways to keep skin healthy, and there also are now many options available to treat skin conditions, if treatment is necessary.

If you think you may have a skin problem, or need to learn how to better care for your skin, consultation with a dermatologist—a physician who specializes in treating the skin and keeping it healthy—may be in order. Skin problems can be difficult to diagnose because many skin conditions share similar symptoms. An evaluation is key to effective treatment.

The Structure of Skin

To understand how to keep your skin healthy, it may help to learn about your skin's structure.

Skin is composed of two layers: the epidermis (the outermost layer of skin—about the thickness of a piece of paper) and the dermis (the middle layer). The thickness of the dermis is variable depending on the location. For example, eyelid dermis is quite thin, but back dermis is about 1/2 inch thick. The epidermis has four layers: the stratum corneum, the granular layer, the squamous cell layer and the basal cell layer.

The stratum corneum or outer layer of the epidermis is the layer of skin that can be seen and felt. Proteins known as keratin, a fatty, waterproof envelope, and flat corneocyte cells make up the stratum corneum. This layer is the barrier between your body and the outside world.

The granular layer produces protein and lipids (fat) for the stratum corneum.

The squamous cell layer produces keratin for the stratum corneum and also transports water. Friction blisters occur in the squamous cell layer.

The basal cell layer is the lowest layer of the epidermis. This is where the skin cells are reproduced and give rise to the more superficial layers of the epidermis. The most common form of skin cancer, basal cell carcinoma, arises from this cell layer. Melanocytes, which produce melanin, or skin pigment, sit along this layer among these cells. Melanoma, one of the two main groups of skin cancer, originates from these pigment-producing cells.