Download Document

Chapter 7 Skin Structure, Growth, and Nutrition
I. ANATOMY OF THE SKIN
A. DERMATOLOGY The medical branch of science that deals with the study of the skin and its nature, functions,
diseases, and treatment
1. Dermatologist A physician engaged in the science of treating the skin, its structures, functions, and diseases
2. Cosmetologist Cosmetologists are allowed to clean skin, preserve the health of the skin, and beautify the skin
depending upon the laws in their state.
3. Esthetician A specialist in the cleansing, beautification, and preservation of the health of the skin on the entire
body including the face and neck. In some states a cosmetologist must also hold an esthetics license to
perform these services.
B. SKIN SPECIFICS The skin is the largest and one of the most important organs of the body.
1. Covers 3,000 (7,620 square cm) square inches
2. Weighs about nine (4 kg) pounds
3. Protects muscles, bones, and nerves
4. Barrier against the environment
5. Eyelids have the thinnest skin
6. Soles of feet are the thickest
7. Continued pressure causes calluses
C. HEALTHY SKIN CHARACTERISTICS Healthy skin is free of visible signs of disease, infection, or injury.
1. Slightly moist
2. Soft and flexible
3. Smooth and fine-grained
4. Possesses slightly acid reaction
5. Reacts quickly to the touch
D. APPENDAGES OF THE SKIN
1. Hair
2. Nails
3. Sweat and oil glands
E. TWO DIVISIONS See Figure 7–1.
1. Epidermis
2. Dermis
F. EPIDERMIS Outermost and thinnest layer; it contains no blood vessels but has many nerve endings.
1. Stratum corneum The horny layer is the outermost layer of the epidermis. Its scale-like cells are constantly shed and
replaced. Cells contain the protein keratin which combines with a thin covering of oil to make the skin water-resistant.
2. Stratum lucidum The clear, transparent layer just under the skin surface; it consists of small cells through which light
can pass.
3. Stratum granulosum The granular layer consists of cells that look like distinct granules. They are dying as they are
pushed to the surface to replace dead cells that are shed from the skin surface layer.
4. Stratum spinosum Just above the basal cell layer; the spiny layer is where the process of shedding skin cells begins.
5. Stratum germinativum The basal cell layer is the deepest layer; it produces new epidermal skin cells and is responsible
for growth of the epidermis. The stratus germinativum contains special cells called melanocytes that produce dark skin
pigment called melanin.
G. DERMIS The underlying or inner layer of skin; also called derma, corium, cutis, or true skin. It is about 25
times thicker than the epidermis. It is highly sensitive and contains blood vessels, lymph vessels, nerves, sweat and oil
glands, hair follicles, arrector pili muscles, and papillae. It is made up of two layers: the papillary or superficial layer and
the reticular or deeper layer.
1. Papillary layer The outer layer of the dermis, lying directly beneath epidermis. It contains small cone-shaped projections
(called papillae) of elastic tissue that point upward to the epidermis. Some papillae contain looped capillaries. Others
contain nerve fiber endings for the sense of touch called tactile corpuscles; they contain some melanin.
2. Reticular layer The deeper layer of the dermis; contains fat cells, blood and lymph vessels, sweat and oil glands,
hair follicles, and arrector pili muscles. It supplies the skin with oxygen and nutrients and contains numerous structures in
its network.
a. Fat cells
b. Sudoriferous glands
c. Blood vessels
d. Hair follicles
e. Lymph vessels
f. Arrector pili muscles
g. Sebaceous glands
h. Nerve endings
3. Subcutaneous tissue Fatty layer found below dermis; also called adipose or subcutis tissue; varies in thickness
according to age, sex, and general health. It gives smoothness and contour to the body, contains fats for energy, and acts
as a protective cushion for outer skin. See Figure 7–2. in the Milady Standard Cosmetology textbook.
G. HOW SKIN IS NOURISHED Blood supplies nutrients or molecules from food such as protein, carbohydrates, and fats
to the skin. The nutrients are required for cell life, repair, and growth. Lymph bathes the skin cells and removes toxins and
cellular waste. Networks of arteries and lymph vessels in the subcutaneous tissue reach the hair papillae, hair follicles,
and skin glands.
H. NERVES OF THE SKIN
1. Motor nerve fibers Distributed to arrector pili muscles attached to the hair follicles. They cause gooseflesh when you
are frightened or cold.
2. Sensory nerve fibers React to heat, cold, touch, pressure, and pain. Send messages to the brain. They are found in the
papillary layer and are abundant in fingertips.
3. Secretory nerve fibers Distributed to sweat and oil glands of the skin; they regulate the excretion of perspiration from
sweat glands and control the flow of sebum to surface of skin.
I. SENSE OF TOUCH The papillary layer of dermis houses nerve endings that provide body with sense of touch. They
register sensations such as touch, pain, heat, cold, and pressure.
J. SKIN COLOR Depends, in part, on blood supply to the skin and melanin
1. Melanin The tiny grains of pigment (coloring matter) deposited in the stratum germinativum of the epidermis and the
papillary layers of the dermis; it protects against UV light.
a. Pheomelanin Red to yellow in color
b. Eumelanin Dark brown to black. See Figure 7–3. in the Milady Standard Cosmetology textbook.
2. Heredity Varies among races and nationalities. Dark skin contains more melanin while light skin contains less.
K. STRENGTH AND FLEXIBILITY Two structures, collagen and elastin, make up 70 OF SKIN percent of the dermis and
give strength, form, and flexibility to skin.
1. Collagen A fibrous protein that gives skin form and strength. Healthy collagen fibers allow skin to stretch and contract. If
fibers become weakened, skin can lose tone and suppleness, wrinkle, and sag.
2. Elastin A protein base similar to collagen that forms elastic tissue. It gives skin flexibility and elasticity
and helps skin regain its shape even after repeated stretching and expanding.
L. GLANDS OF THE SKIN See Figure 7–4. in the Milady Standard Cosmetology textbook. Skin contains two types of duct
glands that extract materials from the blood to form new substances.
1. Sudoriferous or sweat glands Consist of a coiled base, or secretary coil, and a tubelike duct that terminates at the skin
surface to form the sweat pore. Sweat glands are more numerous on palms, soles, the forehead, and armpits. They
regulate body temperature and help eliminate waste; activity is increased by heat, exercise, emotions, and certain drugs.
Excretion of sweat is controlled by the nervous system. Normally one to two pints (1/2 to 1 l) of salty liquid are eliminated
daily.
2. Sebaceous or oil glands Consist of little sacs whose ducts open into hair follicles. They secrete sebum that lubricates
skin and preserves softness of hair. These glands are found everywhere on the body except the palms and soles. Sebum
flows through oil ducts leading to the mouths of hair follicles; when it becomes hardened and the duct becomes clogged, a
comedo (hair follicle filled with keratin and sebum) is formed.
a. Acne A skin disorder characterized by chronic inflammation of the sebaceous glands from retained secretions and
Propionibacterium acnes bacteria
b. Papule A small, round elevation on the skin that contains no fluid but may develop pus
c. Pustule An inflamed pimple containing pus
M. FUNCTIONS OF THE SKIN
1. Protection Protects body from injury and bacterial invasion. The outermost layer is covered with thin layer of sebum to
make it waterproof.
2. Sensation Responds to heat, cold, touch, pressure, and pain. See Figure 7–5. in the Milady Standard Cosmetology
textbook.
3. Heat regulation Protects the body from the environment
4. Excretion Perspiration takes salt and other chemicals with it.
5. Secretion Oil lubricates skin and keeps it soft and pliable and keeps hair soft; emotional stress can increase the flow
of sebum.
6. Absorption Very few ingredients can penetrate the epidermis. Small amounts of fatty materials may be absorbed
between the cells and through the hair follicles and sebaceous gland openings.
III. NUTRITION AND MAINTAINING SKIN HEALTH The old adage “You are what you eat” still holds true. To keep the
body healthy, people must ensure that what they eat helps regulate hydration (keeping a healthy level of water in the
body), oil production, and overall function of the cells. Skin disorders, fatigue, stress, depression, and some
diseases can be caused by an unhealthful diet or improper hydration.
A. ESSENTIAL NUTRIENTS These essential nutrients are obtained through eating and drinking. The body cannot make
nutrients in sufficient amounts to sustain itself properly.
1. Carbohydrates
2. Fats
3. Proteins
4. Vitamins
5. Minerals
6. Water
B. FOOD PYRAMID GROUPS The U.S. Department of Agriculture (USDA) developed a food pyramid to help people
determine the amounts of food they need to each from the five basic food groups. See Figure 7–6. in the Milady
Standard Cosmetology textbook.
1. Grains
2. Vegetables
3. Fruits
4. Milk
5. Meat, poultry, fish, and beans
C. DIETARY GUIDELINES
1. Eat a variety of foods.
2. Eat fruits, vegetables, Grains should be low in fats, saturated fats, and grains. cholesterol.
3. Eat moderate salt and sugar.
4. Drink appropriate water. Divide body weight by two and that is how many ounces of water you should drink daily.
5. Minimize alcohol intake.
6. Exercise appropriately.
7. Maintain/improve your weight. Read food labels.
D. VITAMINS AND DIETARY Vitamins A, C, D, and E have all been shown to SUPPLEMENTS have positive effects on
the skin’s health when taken internally. Become familiar with the recommended daily allowance (RDA) of vitamins and
minerals. Helpful vitamins are listed.
1. Vitamin A Supports overall health of skin and aids in the health, function, and repair of skin cells; improves
elasticity and thickness
2. Vitamin C Needed to repair skin and tissues. It accelerates skin’s healing processes and can fight the aging process.
It also promotes collagen in dermal tissues.
3. Vitamin D Enables the body to absorb and use calcium; promotes rapid healing of skin
4. Vitamin E Protects skin from harmful effects of the sun’s UV light. See Table 7–1.
E. WATER AND THE SKIN Water is an essential item for life.
1. Composes 50 to 70 percent of body’s weight
2. Sustains the health of cells
3. Aids in elimination of toxins and waste
4. Helps regulate body’s temperature
5. Aids in proper digestion
F. WATER BENEFITS
1. Mild dehydration slows the metabolism by 3 percent.
2. Drinking water reduces hunger pangs.
3. Reduces cracked skin on feet and lips
4. Dehydration causes fatigue.
5. A 2 percent drop in body water can cause fuzzy short-term memory.