- Diseases, Disorders & Conditions
skin structure - parts of the skin and acne
Before we discuss your acne, you need to know something about the skin itself, what purposes it serves and particularly the way it is constructed. Once you have a clear picture in your mind of the different structures of the skin, it will be much easier for you to understand why you have acne and what to do for it.
The skin is not simply a solid mass like a blanket covering the body, but rather a multilayered structure. Each layer is made up of different structures, the parts of which are so small that they can be seen only with the aid of a microscope. When you look at your skin, you see the surface of the topmost layer, which is called the epidermis. It consists of several rows of cells piled one upon another. The outermost cells are toughened to protect the delicate cells beneath. These toughened cells on the surface form the "horny layer" of the skin. On the palms and soles, where the skin needs greater protection, the horny layer is greatly thickened and resembles a pig's hide.
As the skin grows, the horny-layer cells die and are shed, new ones replacing them from below. Normally, this shedding occurs so slowly that we are not aware that it is taking place. But following a sunburn, for example, it occurs rapidly and the peeling which results is familiar to everyone. In acne, the horny-layer cells in and about the oil-gland openings grow more rapidly than they are shed, piling cell upon cell. This is one of the characteristic changes which occurs in the skin with acne. And it will explain a good deal of your trouble.
Directly beneath and attached to the epidermis is the second layer of the skin, which is called the dermis. It is much thicker than the epidermis and it contains many different types of structures. First of all, there are interlacing strands of tissue called fibers which make up the framework of the dermis. Some of these have an elastic quality and keep the skin taut. As we grow older, these fibers lose their elasticity, causing wrinkles. Incidentally, there is not much we can do about preventing wrinkles or even removing them once they appear, despite what you may have heard or read on the subject.
The other fibers which make up the bulk of the dermis framework are known as the connective tissue of the skin. After a deep injury to the skin these fibers overgrow, replacing the cells of the epidermis and even the elastic fibers. It is in this way also that the scars of acne are formed.
In this mesh of tissue fibers are blood vessels, nerves and hair follicles which contain the hair shafts and their roots. The dermis also contains some of the glands of the skin, of which there are two types: the sweat glands and the oil glands.
This drawing shows the layers of the skin and the structures they contain. Notice the thin, horny cell layer lying on top of the rows of epidermis cells. Deep in the dermis you can see a hair root. The hair, lying in its sheathlike follicle, passes through the fibers and cells of the dermis and epidermis and leaves the skin through the follicle opening. Attached to the hair follicle are two sebaceous (oil) glands.
The one on the right side shows the duct which carries the oil from the gland to the hair follicle, through which the oil reaches the surface. Attached to the hair follicle just below this gland is a small muscle of the skin (Erector M). A sweat gland in the subcutaneous tissue sends its duct spiraling upward until it opens on the surface of the skin as a sweat pore.
The tiny blood vessels (capillaries) at the junction of the epidermis and dermis stem from larger vessels in the subcutaneous tissue. Here also can be found the nerve fibers, whose lace-work of delicate branches reaches every part of the skin. The actual thickness of the skin shown in this picture is only about one sixteenth of an inch.
We are interested mainly in the oil glands because their overactivity has so much to do with acne. These vital glands, which are called sebaceous glands, consist of tiny sacs of oil-filled cells. The majority of them are attached to the follicles of the almost invisible hairs of the skin. Their oily secretion, sebum, flows out from the glands through tiny openings into the space between the walls of the hair follicles.
The latter then serve as channels or ducts to carry the oil to the surface of the skin. Sebum is a fatty substance and it acts as a lubricant and protective coating to the skin, keeping it smooth and soft. Late in life the flow of sebum slows down and that is why so many elderly people have dry skin. Too much exposure to the sun, wind and cold can temporarily "de-fat" the skin in the young and old alike. And as you will learn, there are conditions under which the skin becomes too oily, one of which is acne.
The third and deepest layer of the skin, the subcutaneous layer, is mainly a mass of fatty tissue. In it are blood vessels and nerves of larger size than those in the dermis and some sweat glands. It serves as padding for the body as well as support for the two layers of skin which rest on it. There are other structures of the skin which have not been mentioned, but for our purposes we need not discuss them.
The skin as a whole has many different functions. It protects the body from extreme heat or cold. It acts as a barrier to strong sunlight. It serves as a cover for the muscles, tendons and bones, protecting them from exposure and injury.
Through its nerve endings it is the organ which tells us the nature of the world about us by feel and touch. In the same way, it relays messages to our emotions of tenderness and love. In a less tangible but very important way, it is the boundary between each individual and everything else that moves about him. And finally, it has been called the "organ of expression" because it reflects our emotions in so many ways.