CHAPTER 13

The Skin

The largest organ of the body is, surprisingly, the skin. It has many important functions including protecting us from the extremes of temperature and weather, regulating the body's temperature, excreting wastes and water in the form of sweat, and, since it covers the whole body, it provides the brain with a sensitive surface to sense and respond to the environment. Doctors examine the skin because it can provide information to much of what may be going on inside the body.

The skin is examined using two of the doctor's primary methods of examination: observation and palpation.

The skin is made up of three layers: on the surface is a layer of mostly dead cells which are stacked up on one another. This layer is called the epidermis. The next layer is the dermis which lies just below the epidermis. It contains the structures which produce hair (follicles) as well as sebaceous glands which secrete sebum, a waxy, oily substance. The deepest layer of skin is the subcutaneous layer which contains fat, sweat glands and blood vessels.

Basic elements to examination of the skin:

1. Color: Melanin is a pigment in skin which determines its color. Individuals of different races have different skin colors based on the number of melanin cells in their skin which is genetically determined.
   
   Indicators of illness may include pale skin which can be a sign of anemia (low numbers of red blood cells which carry oxygen). Mottled skin with alternating patches of pink and white in a net-like pattern is indicative of severe dehydration or a lack of sufficient blood supply to the skin such as in shock.
   
   In times of severe oxygen deficiency, skin can become blue in color. At other times skin may become yellow in color as when patients have too much of a substance called bilirubin in their blood. Bilirubin is a substance formed when old red blood cells are broken down for recycling in the body. Too much bilirubin in the blood can be caused by too much breakdown of blood cells (such as in several blood and spleen diseases) or by slow processing of bilirubin in the liver.
   
   The skin may also appear bronze in color, indicating difficulty with the body's ability to store iron or other elements such as copper.
   
   The color of the skin does not in itself indicate a diagnosis, but in points the doctor in the right direction to what may be going on.

2. Texture: The general feel of healthy normal skin is smooth, soft and somewhat moist. Doctors feel the skin to determine abnormalities in its texture. Rough skin, for example, can sometimes be a symptom of hypothyroidism, while velvet smooth skin may indicate hyperthyroidism.
   
   

3. Moisture: Skin conditions may be caused or made worse by the lack of moisture in the skin. Dry skin can indicate certain diseases such as hypothyroidism and allergic reactions.
   
   

4. Turgor: The turgor of the skin is a measure of its elasticity. If you take a pinch of a person's skin between your fingers and pull it up into a tent shape and then let go, you will notice that it will bounce back quite quickly, almost like rubber. But skin in a person that is severely dehydrated will not bounce back quickly. In fact, if the dehydration is severe, it may take several seconds for it to slowly resume its previous position. In addition, the skin of elderly people usually has less turgor since with aging it loses much of its elasticity.
   
   

5. Temperature: Since the skin is the largest organ of the body, it receives a larger proportion of the blood flow from the heart. The amount of blood flow to the skin is carefully controlled and is not a fixed percentage. The blood vessels which feed the skin can enlarge or constrict in such a way as to send more or less blood to the skin. When the body is hot, more blood is sent to the skin to produce sweat to allow for cooling. When the body is cool, blood is shifted away from the skin so that heat is not lost. In addition, when there is significant blood loss or dehydration, the blood can flow from the skin to the vital organs such as the heart and brain. Thus the temperature of the skin is helpful in diagnosing medical problems.
   
   

6. Mucous membranes: Although not a part of the external surface of the body, mucous membranes (located under the eyelids, in the mouth and nose, and in the vagina and rectum) can help determine the hydration status of the patient. A moist mouth is usually indicative of good hydration, while a dry mouth may indicate dehydration.
   
   

7. Lesions: Perhaps one of the most important parts of examining the skin is looking for lesions such as rashes, lumps, knots, or injured areas. These can be important clues to skin diseases as well as indications of diseases inside the body. For example, there are several changes which occur on the skin in certain places on the body when cancer is developing. These can serve as early signs to the doctor that cancer may be developing.
   
   Doctors ask basic questions when confronted with abnormal skin areas: Questions, such as, "Is it flat or raised?" "Does it have smooth or irregular borders?," "What is its color?," "What is its texture?," "Does it have fluid or pus in it?," "What is its size?," "Where is it located on the body?," "Are there groups of lesions arranged in any particular way?," and "Is it painful or does it itch?" The answers to all of these questions help in making an accurate diagnosis.

Skin Cancer:
Skin cancer is the most common type of cancer in the United States and affects millions of people each year. It is important to diagnose early, since all types of skin cancer are curable if treated early enough. There are three main types of skin cancer, all related to sun exposure. People with fair skin who have been exposed to high levels of sun exposure and sunburn (especially in the early years of life) are at higher risk for skin cancer.

Basal cell cancer: Appears as smooth and shiny raised lesions, sometimes with discoloration or visible blood vessels near the surface of the skin. This cancer rarely spreads to other parts of the body but can be locally disfiguring.

Squamous cell cancer: Comprised of rough nodules with scabs or scales, which are often inflamed around the edges. Squamous cell cancer, like basal cell cancer, rarely spreads to the rest of the body, but sometimes it can. There is a higher risk of spread if the cancer is on the lip, temple, scalp, ears or genital areas.

Malignant melanoma: a dangerous kind of cancer of the pigment cells (melanocytes). This kind of cancer is the most deadly. After it spreads to other organs such as the liver, it is not considered curable. Caught early, the prognosis (outcome) depends on the depth of the tumor and whether or not it has spread. Melanomas are usually dark brown in color, darker than freckles. Some dark birthmarks have a risk of becoming melanomas and should be watched closely for any of the changes that follow:

Signs of Malignant Melanoma:
Asymmetry: the lesion is not symmetrical
Borders are irregular
Color variegation: the color is different in different areas of the lesion
Diameter: greater than 6mm
Elevation: above the skin surface

The most important rule for diagnosing all skin cancers is looking for change. If you have any areas which concern you, have someone look carefully at them and even note (draw) their size, shape, and color. If they change over time, have a doctor look at them. Also, if a skin lesion is painful, itches, and bleeds, these can be early signs of a developing cancer.

The Appendages:
The skin has three main attachments or appendages: the hair, nails, and sweat glands.

1. Hair: The appearance of the hair can provide the doctor with medical information. There are several conditions that can affect the hair. Among these are lice, which can infest the hair, and some fungi which infect the skin of the scalp and hair follicles. These conditions are usually quite obvious and are easily treated. Hair loss is a common problem which affects some people. Hair loss is most frequently determined genetically but is also related to age and gender. There are, however, several types of hair loss conditions that are related to skin diseases and certain stresses. Careful examination can help to distinguish the different causes of hair loss. In addition, certain metabolic diseases of the body such as hypothyroidism can cause hair loss.
   
   

2. Nails: Examination of the nails can be a clue to diseases also. Here are a few examples:
   Clubbing: This is a condition in which the nails become dome-shaped instead of flat and the angle between the nail and skin increases. This is caused by a long-term lack of oxygen in the tissues and is commonly found in people with emphysema and lung cancer. It can also affect children with heart disease.
   
   Pitting: These are small, crater-like pits in the nails. Commonly found in individuals having a skin disease called psoriasis.
   
   Spooning: This occurs when there are not enough red blood cells circulating in the blood giving the nails a scooped-out or spoon-shaped appearance.
   
   Beau's lines: are ridges which occur in the nail in a transverse direction. They are signs of recent severe illness. If, for example, a person has a sudden severe illness and required hospitalization and even intensive care, the body, because of this great stress, can delay making good healthy nail tissue for several days (while it concentrates on other things). When the person recovers and normal nails begin to grow, a small ridge is left which represents the time of the acute illness.
   
   Splinter Hemorrhages: These are small red/brown lines which run longitudinally along the nail. They represent areas of bleeding under the nail bed and can occur when people have serious infections of their heart valves. When this happens, small infected pieces of the damaged heart valve can be broken off by the circulating blood and travel downwards in the bloodstream. When they finally get trapped in a small vessel (such as under the nail), they cause a small area of bleeding and infection. This bacterial infection of the inner surface of the heart and valves is called bacterial endocarditis. Manifestations of this same disease can cause changes in the palms of the hands and soles of the feet as well as small areas of bleeding in the retina.

3. Sweat glands: These are found over most of the skin surface and secrete waste products and water in the form of sweat. These glands are not usually examined since they are microscopic and buried under the skin. There is one test done in the laboratory which tests the composition of sweat for its content of chloride which is abnormal in persons with cystic fibrosis.

Chapter 14