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The Human Skin—Engineered by God
| by | Taylor Richardson |
In what single place can you find the following things: 19 million cells, 625 sweat glands, 90 oil glands, 65 hairs, 19 feet of blood vessels, and 19,000 sensory cells? The answer: in one square inch of human skin! The human skin is considered the largest organ in the body (about 16% of your body weight), and covers an area of 20 square feet. Your skin, or integument, has many different protective and metabolic functions that help keep your body stabilized.
SKIN LAYERS
You have two skin layers. The outer layer, the epidermis, consists of rows of cells about 12 to 15 deep, and is between 0.07 and 0.12 millimeters thick (about as thick as a piece of paper). This top layer is composed mainly of dead cells that are being replaced constantly by newer cells. Isaac Asimov explained the process in his book, The Human Body:
The cells at the base of the epidermis are alive, and are constantly growing and multiplying so that cell after cell is pushed upward and away from the dermis. Without a blood supply, the cell dies and much of it, aside from the inert keratin, atrophies. The vicissitudes of existence are constantly rubbing away some of this dead material from the surface of our body, but this is constantly being replaced from below, and we retain our epidermis ever fresh (1963, pp. 258-259).
Sometimes, when areas of the skin are subjected to constant friction, the epidermis responds by thickening itself in that area, creating a callus. These patches of hard skin usually are found on the soles of feet of people who walk barefoot, and on the hands of farmers. It is as though the dermis had traded in its thin plastic gloves for a pair made of leather.
The inner layer, or dermis, is a spongy, leathery area that is about one to two millimeters thick, consisting mainly of collagen (a fibrous protein found in the skin) connective tissue. The dermis is joined to the epidermis by a grooved surface that contains nerves, blood vessels, hair follicles, sebaceous glands, and sweat glands, all of which have important functions. Each hair follicle, for example, contains one hair that transmits the reception of touch to sensory nerves around the follicle. Sebaceous glands produce a waxy secretion called sebum, which helps to waterproof the skin. Sweat glands help to cool the skin and keep the body temperature constant.
FUNCTIONS OF SKIN
One of the most important functions of the skin is to provide us with a sense of touch. Werner Gitt explained it best:
The most important property of the skin is that it contains our sense of touch… The sense of touch is difficult to investigate. All other senses have a definite key organ which can be studied, but the skin is spread over the entire body and cannot easily be delimited or “switched off.” In the case of vision, scientists can observe blind persons to learn more about seeing, and they can study deaf people to learn more about hearing. But this is impossible for the sense of touch (1999, p. 41).
Receptors (from the Latin word receptor, meaning “recorder”) located at the ends of nerve fibers are used to detect stimuli and convert them into neural impulses to be sent to the brain through the peripheral and central nervous systems. Receptors also are located in the internal organs, muscles, and skeletal joints, and can detect information such as the temperature of a cup of coffee or the roughness of sand paper. Although we “touch” with our epidermis, the sense of touch actually is recorded in the dermis and passed on to the central nervous system.
Another important function of the skin is that it helps the body keep a constant temperature. Gillen, et al., wrote: “The word homeostasis comes from two Greek terms, homeo (alike or the same) and stasis (standing or remaining). Thus the word means remaining the same” (1999, italics, parenthetical items, and emp. in orig.). A person’s average body temperature is 98.6 degrees Fahrenheit, but if it increases by 7 or 8 degrees, and remains there for any of length of time, a person will almost certainly die. So how does the body keep a generally constant temperature? It does so via a method of cooling known as perspiration. The main sources of body heat are the internal organs that work all the time, such as the heart and kidneys. The heat created by these organs is carried off by the blood and distributed evenly throughout the body. This is an efficient way to diffuse the heat at a slow pace, but what happens when the body must get rid of heat quickly? Asimov explained:
We are equipped with tiny glands distributed all over our skin, about two million of them all together, the purpose of which is to bring water to the surface of the skin. On the surface this water is vaporized and heat is in this manner withdrawn from the body. The glands are sweat glands and the liquid produced is sweat or perspiration. A sweat gland consists of a tiny coiled tube, the main body of which situated deep in the dermis. The tube straightens out finally and extends up through the epidermis. The tiny opening on the surface is a pore and is just barley visible to the naked eye. When you are working or playing hard, and heat production is increased, the sweat glands accelerate their production of perspiration. This is also true when the temperature is unusually high. The rate of production may then outstrip the rate of evaporation, particularly if humidity is high, since the rate of evaporation declines with the rise in humidity. Perspiration will then collect on the body in visible drops and we are conscious of sweating (p. 265, italics in orig.).
The temperature determines how many sweat glands a person has, in the same way that the amount of sunlight determines how much melanin is in the skin. People who live in hot, humid climates tend to have more sweat glands, and produce perspiration with a smaller concentration of salt, than people living in colder, drier climates.
The skin also acts like a chemical-processing plant for the entire body. When you are outside, the skin absorbs ultraviolet rays from the Sun, and then uses them to convert chemicals into vitamin D. This vitamin is very important to our body because it helps stimulate the absorption of calcium. Without calcium, our bones grow thin and brittle, eventually leading to diseases such as rickets and osteomalacia (skeletal diseases that weaken bones). In addition, the epidermis contains a special pigment called melanin, which is responsible for the variety of color in our skin. It also acts as a protection against ultraviolet light. The melanin absorbs ultraviolet light without harming itself, and acts as a protective covering over the area beneath it. Like vitamin D, melanin is formed by the exposure to sunlight, so people in tropical regions have more melanin to protect them from the harmful ultraviolet rays, while people in northern regions have little traces of melanin because the Sun is rarely out for long periods of time. But not all people are able to produce melanin in their bodies. Occasionally, individuals are born who are incapable of forming any melanin at all. Their skin and hair are pinkish-white and their eyes are pinkish-red, because the tiny blood vessels are visible in the iris of their eyes (where there are typically colors such as blue, green, hazel, and brown). A person with this condition is referred to as an albino, indicating that they lack pigmentation in their skin. Albinism is not limited just to humans, but also is found in other species of animals as well (e.g., the white rat, the white elephant, the white tiger, etc.).
Furthermore, the skin also helps protect the inside of the body. If you have ever been to an amusement park, you probably have seen the bumper cars that you can drive to bump into other cars. Collisions in those cars are perfectly safe because of the rubber rings that surround the cars. The skin is like those rubber rings in that it acts like a shock absorber when you fall, protecting all of your internal organs. If we didn’t have this “shock absorber,” it would be practically impossible to do physical activities without damaging internal organs or bruising easily.
It is impossible that evolution could have produced such an important and complex organ as the human skin. The many intricacies of its functions are evidence of a Creator. One writer remarked: “The skin is a miracle of evolutionary engineering: it waterproofs the body, blocks out and destroys harmful bacteria, regulates temperature, and continuously communicates with the brain” (McCutcheon, 1989, p. 113). Yes, the skin is a “miracle” all right—but not a miracle of evolution. And yes, the skin was “engineered”—but the engineer was God!
REFERENCES
Asimov, Isaac (1963), The Human Body (New York: New American Library).
Gillen, Alan L., Frank J. Sherwin III, and Alan C. Knowles (1999), The Human Body: An Intelligent Design (St. Joseph, MO: Creation Research Society).
Gitt, Werner (1999), The Wonder of Man (Bielefeld, Germany: Christliche Literatur-Verbreitung E.V.).
McCutcheon, Marc (1989), The Compass in Your Nose (Los Angeles, CA: Jeremy P. Tarcher).