PDC Test - The Skin
You can earn 0.25 PDC by passing the exam following this article, which has been approved for publication by NCRA's Council of the Academy of Professional Reporters.
The questions are based on the material in the article but some may require additional research. Send your answer sheet to NCRA's Continuing Education Office, 8224 Old Courthouse Road, Vienna, VA 22182, and enclose a check for $40 (member) or $50 (non-member) to cover the processing fee.
Is the skin an organ of the human body? Perhaps you're not used to thinking of it as an organ, but the skin is one of the most important units of the body. And, although it is not as thick as other important organs, the skin of an average adult has over 3,000 square inches of surface area. It weighs about six pounds, being twice as heavy as the liver or brain. And the skin receives one third of all the blood circulating throughout the body.
The skin performs a number of important jobs. Among these are protecting the body against invasion of bacteria, against injury to the more sensitive tissues within the body, against the rays of the sun, and against the loss of moisture.
The skin also serves as an organ of perception for the nervous system. If we could see one square inch of skin under a microscope, we would find about 72 feet of nerves. We also would be able to count hundreds of pain receptors, plus pressure receptors, heat receptors, and cold receptors.
Still another job performed by the skin is that of temperature regulation. One square inch of skin also contains about 15 feet of blood vessels which dilate, or grow larger, when the body needs to lose heat. And the blood vessels constrict, or become narrower, when the body must reduce the amount of heat loss through the skin.
When the surrounding air is comparatively warm, the skin is cooled by moisture secreted by the sweat glands. There are about two million sweat glands over the surface of the body, and they occur in the greatest concentration on the palms of the hands and the soles of the feet. The sweat glands are controlled by a heat regulator in the brain. The moisture secreted by the sweat glands cools the body by evaporation.
A function of the skin sometimes used by doctors is its ability to absorb certain drugs. Some chemicals placed on the skin can be detected in the saliva 20 minutes later. The chemicals enter the body through the follicles, or pits from which hairs grow, and the glands.
The surface of your skin may look smooth, but if you examine it under a magnifying glass you'll see countless ridges and valleys. You also will see different patterns of skin texture on the palm of your hand and on the back of your hand.
The skin generally is soft and flexible, and more elastic in younger people. It varies in thickness from about 1/50 of an inch on the eyelids to as much as 1/3 of an inch on palms and soles.
Three layers of tissue make up the skin: the epidermis, the dermis, and the subcutaneous layer. The subcutaneous layer contains many fat lobules, blood vessels, and nerves. It links the dermis, or middle layer of the three, with tissue covering the muscles and bones. It also serves as a smooth and springy base for the skin.
As persons grow older, the fatty tissue is absorbed. This causes the outer layers of the skin to form uneven folds, or wrinkles.
The dermis, sometimes called the "true skin," is atop the subcutaneous layer. It varies in thickness in different parts of the body and contains blood vessels, nerves, nerve receptors, hair follicles, sweat glands, and oil glands.
At the top of the dermis is a layer of tiny cone-shaped objects called papillae. There are perhaps 150 million papillae scattered over the body. They are more numerous in areas such as the fingertips, where the skin appears to be more sensitive. Nerve fibers and special nerve endings are found in many of the papillae and, again, papillae with nerve endings occur most frequently in areas where the sense of touch is better developed.
The papillary layer fits snugly against the outer layer of skin, the epidermis, which has ridges corresponding to those of the papillae. The ridges prevent the skin layers from slipping.
The ridges on the surface of the fingertips form whorls and other patterns, which we call fingerprints. Similar ridges appear on the soles of the feet. Because it is unlikely that two persons will have exactly the same pattern of ridges, fingerprints are used by police to identify criminals and by hospitals to identify babies. The possibility that two persons would have the same set of fingerprints has been estimated to be one chance in 24 billion.
The top layer of the epidermis, sometimes called the horny layer, is made of scales that actually are dead skin cells. They gradually flake off or soak off when wet. The horny layer is constantly being replaced by cells pushed toward the surface as new cells are formed in the deeper layer of the epidermis. As the skin cells move toward the surface, their jellylike living substance -- protoplasm -- is converted into horny material.
In the deeper layer where the new cells are being formed, the skin may be colored by a pigment called melanin. Its purpose is to prevent the more dangerous rays of the sun from damaging tissues. Skin color also is influenced by a second, yellow pigment and by the presence of blood vessels in the dermal layer.
We're all familiar with the changes in the skin produced by exposure to sunlight. The effects of sunlight vary with the time of the year, the geographical area, and the hour of the day. Generally, after about 20 minutes' exposure to the summer sun at midday, the skin shows a reddening. The reddening, called erythema, may not appear until several hours after exposure to the sun. If the "dose" of sunlight is intense, the reddening may be followed by blistering and peeling of the outer layer of epidermal cells.
If the erythema is not severe, it will fade in a few days and the skin will gradually acquire a brown coloration that we call suntan. The brown color is produced by the melanin pigment which usually is present at the bottom of the epidermal layer. When skin is exposed to the sun, it is believed that melanin pigment moves toward the surface of the skin and is replaced by new melanin in the lower cell layer. One or two weeks may be required to develop a suntan by moderate daily doses of sunlight. The tan will begin to fade if occasional exposure to sunlight is not continued.
The redness of erythema is caused by dilation, or swelling, of the blood vessels in the papillae beneath the epidermis. The dilated vessels, of course, permit a larger amount of blood to flow through the dermis.
Freckles are caused by small areas of melanin pigment. They usually fade somewhat during winter months and increase in prominence during the summer.
Two main types of glands are located in the dermis. One, already mentioned, is the sweat gland. Under the microscope it appears as a tightly coiled tube deep in the dermis with a corkscrew-like tubule that rises through the epidermis to the surface of the skin.
The second type is the sebaceous or oil gland. The oil glands usually occur in or near a hair follicle and are located in all parts of the skin except on the palms of the hands and soles of the feet. They are particularly common in the skin of the face and scalp.
The glands are flask shaped and contain an oily substance that is constantly being produced by the glands as the fat lobules change into oil droplets and move toward the surface of the skin. The purpose of the oil is to keep the hair and skin from becoming dry and brittle. The ceruminous glands of the ear, which produce ear wax, are similar to the oil glands of the skin.
Occasionally, especially during adolescence, an oil gland may become plugged by an overgrowth of cells. The oil continues to fill the duct of the gland and forms a blackhead or a pimple. When plugged oil cells become numerous, the condition may be called acne. The condition can be improved by frequent washing of the skin with soap and water to remove the excess oil.
Several kinds of hair are part of the skin. They range in texture from the soft, almost invisible hairs on the forehead to the long hairs of the scalp, and the short, stiff hairs on the eyelids. Like the oil glands, hair occurs on all parts of the skin except the palms and soles.
Each hair has a root, which is anchored at the bottom of a microscopic shaft called a follicle. It also has a shaft which extends past the top of the follicle. The follicle enters the epidermis and passes deep into the dermal layer at an angle. The follicles of long hairs may extend into the subcutaneous layer. Oil, or sebaceous, glands empty into the follicle. At the root of the hair is a cone-shaped papilla that is similar to the peg-like papillae that underlie the ridges of the fingers, palms, and soles.
The shaft of the hair is covered with tiny, overlapping scales. An inner layer of cells in the hair shaft contains the pigment that gives the hair its color; in white hair the cells contain air. Curly hair appears flattened when seen, in cross section, under a microscope. Straight hairs appear round or oval shaped in cross section.
Attached to each hair follicle is a small bundle of involuntary muscle fibers. Under the influence of cold or emotions, the muscle fibers contract and the hair becomes erect. The action of the tiny muscles also produces "gooseflesh."
The hair follicles develop as downgrowths of the layers of the skin. The hair then grows outward from the bottom of the follicle. Thus, hair actually is a special form of the skin itself. In a somewhat similar manner, the fingernails and toenails are a specialized form of skin. The thin layer separating the dermis and epidermis, known technically as the stratum lucidum, becomes thick and hard as the fingers and toes develop. The fully developed nail then overlays a modified part of the dermis that is the bed of the nail. The base of the nail is covered by epidermis.
The nail bed contains ridges which are rich with tiny blood vessels. The blood vessels give the area under the transparent nail its red coloration. Near the base, or root, there is less blood circulation and the nail is not as firmly attached to the nail bed. This explains why the lunula, or half-moon, area of the nail has a whiter coloration.
The rate of growth of nails varies and depends upon such factors as the age of the person and the season of the year. For example, nails grow faster in young people and during the summer months.
The skin is richly supplied with small blood vessels. We already have noted that the blood supply in the skin accounts for the reddening of sunburn and the coloration of the fingers beneath the nails. The blood vessels also account for the reddening of the skin when we blush.
Many of the so-called birthmarks get their coloration from the tiny blood vessels concentrated in a small area of the skin. Other birthmarks are caused by patches of pigment in the skin and are similar to freckles. Moles also are pigmented patches.
Humans with little or no pigment in their skin are called albinos. The skin color is whitish or pink. The hair is white. Some persons have streaks or patches of white hair due to partial albinism. True albinos cannot expose their skin to summer sunlight, and their eyes are unusually sensitive to intense light.
This article and accompanying test were prepared by BAPR member Nancy Patterson of Los Angeles, California. The article, "The Skin," is reprinted by permission of the American Medical Association from The Human Machine, copyright 1979.
Test for "The Skin - CEU Exam"
Now it is time for the test on what you have read. Most of the answers to the questions will be found in the article. However, for some questions it will be necessary to consult a medical dictionary.
1. The "true skin" is called the
C. subcutaneous layer
D. horny layer
2. When the body needs to lose heat,
A. the blood vessels dilate
B. the blood vessels constrict
C. perspiration decreases
D. fat lobules proliferate
3. As we age, wrinkles form primarily because
A. the amount of melanin increases
B. sebaceous glands decrease production
C. adipose tissue is absorbed
D. there is an increase in keratinocytes
4. Administration of drugs that are absorbed through the skin is called
5. Acne vulgaris is a disorder of the
B. sebaceous glands
C. sudoriferous glands
6. A circumscribed stable malformation of the skin is known as a
7. A malpighian cell is also called a
A. subcutaneous cell
8. Most similar to the sebaceous glands of the skin are the
A. gingival glands
B. adrenal glands
C. solitary glands of the large intestine
D. ceruminous glands of the auditory meatus
9. A scleroprotein which is the principal constituent of the epidermis is known as
10. Which usually is not characteristic of a keloid scar?
A. progressive enlarging
B. an irregular shape
C. sharp elevation
D. dark or black coloring
11. On an average adult, how many square inches of surface area does the skin cover?
12. Under a microscope, the shaft of a curly hair characteristically will
A. contain air
B. contain more melanin than an average hair
C. be flattened
D. exhibit dilated capillaries
13. The area of the fingernail with less blood supply is called the
A. nail bed
14. A skin disorder caused by a tiny parasite is known as
15. The medical term for "shingles" is
C. impetigo contagiosa
D. herpes zoster
16. An acute inflammatory skin disease caused by staphylococcus or streptococcus organisms is known as
17. "Gooseflesh" is caused by
A. contraction of the musculi arrectores pilorum
B. keratinizing of the cells of the cortex
C. flaking of the cells of the stratum corneum
D. the acidic concentration of the stratum corneum
18. Freckles are caused by
A. erythematous reaction to sun
B. small areas of melanin pigment
C. irregular capillary supply to the subcutaneous tissue
D. alkaline rather than acidic condition of the stratum corneum
19. The gradual flaking of the top layer of the epidermis is called
20. The medical term for hives is
|Answer Sheet for "The Skin"
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