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In Smart Medicine for Your Skin, board-certified dermatologist Jeanette Jacknin provides the latest information and advice on caring for skin and keeping it healthy. Written in an accessible A-to-Z format, this book incorporates both alternative and conventional therapies, and explores effective remedies for everything from common acne to diminishing wrinkles. It also offers helpful tips on the care of hair and nails.
This comprehensive, balanced resource will help you make radiant, healthy skin a reality.
Understanding Your Skin,
Hair, and Nails
I'd like to introduce you to several parts of your body that you see and feel all the time, but yet may still be a mystery to you—your skin, hair, and nails. You are covered in a wonderful, very large organ: the skin. You are continually grooming your skin's appendages, your hair and nails, to create a certain impression. As each of us knows, the skin is very important in social and sexual functioning. People with hyperpigmented skins, hypopigmented skins, and major facial blemishes often have their sense of well-being and self-worth lowered. Even the normal skin changes that come with aging—male pattern baldness, increased facial hairiness in women, and wrinkling—can cause us much anxiety. People also decorate their skin, hair, and nails with such items as nail polish, false fingernails, skin piercings, earrings, and tattoos to gain social acceptance and attention. It is impossible to overemphasize just how important the skin is to our whole way of interacting with others and our view of ourselves.
So hang on. You are about to start a fascinating trip into the world of your own skin. This section is not meant to be a technical medical synopsis of the anatomy and physiology of the human skin. However, it is intended to give you at least a general understanding of how the skin, hair, sweat glands, and nails are put together and how they work. That way you will have some background knowledge with which to make intelligent decisions about skin disorders and treatments. We will start with some basic skin anatomy. Then the basic types of skin lesions and the terms that skin doctors, or dermatologists, use are described. Finally, we explore hair, sweat gland, and nail anatomy.
STRUCTURE OF THE SKIN
Your skin is made up of three major layers: the epidermis, the dermis, and the subcutaneous tissue. The thick dermis contains hair shafts, sebaceous (oil) glands, sweat gland ducts, nerves, and blood vessels. The subcutaneous layer is full of fat, blood vessels, nerves, and the base of sweat glands. (See Figure 1.1.)
The epidermis is the outermost layer of the skin. It makes proteins for skin-cell growth, and also makes melanin and keratin, which protect the body from harmful substances in the environment. Keratin is a compact protein that provides a waterproof barrier to protect the body from environmental pollutants such as cigarette smoke. Melanin is a pigment in the epidermis that protects the skin and body from sunlight.
The cells of the epidermis multiply constantly, and they replace themselves approximately once every twenty-eight days. Basal cells from the bottom of the epidermis travel upward and turn into more mature, flatter squamous cells, replacing squamous cells at the top of the epidermis as they die and flake off. Cell turnover time gets longer with age and dramatically shorter in disorders such as psoriasis.
The dermis, the layer below the epidermis, is a complex network of collagen and elastic fibers, blood vessels, lymphatic vessels, nerve fibers, sweat glands, sebaceous glands, and hair follicles. Collagen and elastic fibers give flexibility, strength, and a nice tone to the skin. Sun exposure and aging cause these fibers to become damaged or reduced in number, and wrinkling and sagging of the skin becomes noticeable. Blood vessels supply blood to nourish the dermis and epidermis, remove toxins, and help to regulate body temperature. Age or cigarette smoking leads to reduced blood flow to the skin, and the skin becomes pale and sallow. Increased local blood flow to the skin, on the other hand, makes the complexion appear rosy and fresh. Lymphatic vessels in the dermis (as well as throughout the body) make, store, and carry inflammation- and infection-fighting white blood cells to points where they are needed.
Nerve fibers in the dermis convey our sense of touch, both pleasurable and painful. Sweat glands work with the blood vessels in the dermis to help control body temperature by producing perspiration, which is secreted onto the outer layer of the epidermis. There it evaporates, cooling the skin. Sebaceous glands produce sebum (oil), which keeps the skin moist and smooth. Too much sebum can lead to acne, while insufficient sebum production, common with aging, contributes to dry skin and fine wrinkles. Hair follicles produce hair and provide a channel to allow sebum and sweat to exit from their respective glands to the skin's surface.
Several important biochemical reactions take place in the skin, the most well known being the role of the skin in vitamin-D synthesis. The skin is also involved in the metabolism of androgen, a type of steroid hormone, and it has receptors for other steroid hormones as well, including estrogen, progesterone, and glucocorticoids, as well as for vitamin A.
The skin is an important site of immunological activity, with many specialized cells in both the epidermis and the dermis. A variety of cells and chemical messengers are very important in starting and increasing the body's responses to immunological threats.
Under the dermis is the subcutaneous tissue, which is made up mostly of fat used for insulation and storage of calorie (energy) reserves. Importantly, subcutaneous tissue also acts as a storage site for chemicals, drugs, and nutrients.
In disease, some component or components of the epidermis, dermis, or subcutaneous tissue may be affected by thickening (or too much of that component), thinning (or too little of that component), or disruption of that component. Doctors describe skin lesions according to what part of the epidermis or dermis they affect, and in what way, and what the lesions look like to the human eye and under the microscope.
Primary lesions—early, uncomplicated skin changes—are described by dermatologists as macules, papules, plaques, nodules, wheals, vesicles, bullae, and pustules, depending on their size and other characteristics. A lesion that has undergone some type of natural evolution from its early stage or that is artifically altered in some way (scratched or picked at, for example) is considered a secondary lesion. These include crusts, scales, erosions, ulcers, fissures, atrophy, and scars, and they form after the primary lesions. Other types of lesions, classified as special skin lesions, include excoriations, comedones, milia, cysts, burrows, lichenification, telangiectasia, petechiae, and purpurae. For descriptions of the characteristics of these various types of lesions, see Table 1.1.
Skin lesions can be arranged in different ways. The individual lesions can be arranged in lines, circles, gyrating patterns, groups, or not show any particular arrangement. The presence of several or many lesions can be characteristic of a particular skin problem.
HAIR AND HAIR FOLLICLES
There are three types of human hairs: lanugo, vellus, and terminal. Lanugo is a type of soft hair that covers the body of the human fetus. Vellus hairs are fine and cover most of the bodies of children and adults. The long, coarse, pigmented hairs of the scalp, beard, eyebrows, eyelashes, underarms, and, in adults, pubes are terminal hairs. Terminal hairs differ in structure from lanugo and vellus hairs in that they have a central core, or medulla.
During its lifetime, an individual hair follicle may produce different types of hair. Genetic and hormonal influences determine the increase in hairiness around puberty and throughout adult life, as well as the loss of terminal hairs on the scalp with age that is commonly known as male pattern baldness.
Each part of the body has its own genetically determined pattern of hair growth, with individual hairs growing for a set period of time. This period is much longer for scalp hairs, which can grow for longer than three years and reach the mid-back. Pubic and eyebrow hair grows actively for only a few months. This active growing phase is called the anagen phase. After the anagen phase comes the resting phase, or catagen phase. Finally, during the telogen phase, the resting hair is shed. A new hair then normally develops from the same hair follicle and the process repeats itself. Figure 1.2 illustrates how a hair develops, with separate layers with specialized cells.
The hair follicles are set into the dermis at an angle, with the end, or bulb, setting deep down, just above or in the subcutaneous fat. The hair bulb contains a group of cells that divide and diversify to produce the early hair shaft. The hair bulb also contain melanocytes, which produce pigment. The hair shaft, as it grows toward the mouth of the hair follicle, consists of several tubular layers. The medulla is the central core, present only in terminal hairs. The cortex surrounds the medulla, and keratinization (deposition of a layer of keratin, a tough protein) takes place here. The cuticle, a layer of overlapping keratinized plates, lies outside the cortex. The inner root sheath and the outer root sheath lie in concentric layers outside the cuticle.
Partway up the hair follicle, a duct delivers sebum, or lipid (oil), from the attached sebaceous gland onto the surface of the hair. Thus, the hair's surface and then the skin's surface is lubricated with lipid. Figure 1.3 depicts a sebaceous gland joined to a hair follicle.
Hair is generally cosmetically pleasing and has a lot to do with our self-image, self-esteem, and attraction of the opposite sex.
Humans have two kinds of sweat glands: eccrine and apocrine.
The true sweat gland is the eccrine gland. About 3 million of these are present from birth. Sweat glands are present almost everywhere on human skin, except at the junctions between mucous membranes and skin. They are tiny coiled structures, ascending from the junction between the dermis and the subcutaneous fat to the skin's surface. Most of the sweat glands respond to body temperature, increasing their output of salty water when the body becomes hot, and functioning to dispel heat from the body. The eccrine glands on the palms of the hands, the soles of the feet, the underarms, and the forehead also respond to emotional stimuli, such as pain, fear, or anger. Figure 1.4 is an illustration of how a typical eccrine sweat gland appears in the skin.
Apocrine sweat glands are also coiled structures with a duct, but they open into associated hair follicles, just like sebaceous glands do. They are mostly found under the arms, on the scalp, around the nipples, near the navel, and in the outer ears, eyelids, and perineum, or genital area. At puberty, these glands begin to secrete a milky substance that forms when portions of the apocrine cells' cytoplasm (the semiliquid substance that makes up the living matter of cells) separate out, enter the duct, and go through it up to the skin surface. Apocrine glands have a nerve supply, and also depend on the presence of male hormones, or androgens, to trigger secretion of their milky substance. At this time, we know of no function for the apocrine glands in people, although it is known that they serve as a source of sexual scent hormones, or pheromones, in other mammals. Figure 1.5 shows how an apocrine sweat gland looks in your skin.
The nail unit consists of the nail plate and the tissues around and under it. The area of skin that surrounds the cuticle is known as the nail fold (that at the bottom of the nail is the proximal nail fold; that on the sides is the lateral nail fold). The cuticle arises from the cornified, or hardened, layer of the proximal nail fold and extends a few millimeters onto the surface of the nail, known to dermatologists as the nail plate. The proximal nail fold covers the white part, or lunula, of the nail. The lunula is most visible on the thumbnails. Figure 1.6 depicts the anatomy of a nail.
The nail plate rests upon the tissues of the nail bed. It is made up mostly of keratin, a protein rich in sulfur-containing amino acids, which gives the nail its strength and hardness. Contrary to common belief, calcium is present only in tiny amounts in the nail plate and does not contribute to the hardness of nails. Fingernails grow by about 0.1 millimeter—less than a hair's breadth—a day. This means it takes about six months for a fingernail to grow back completely if it is removed. Toenails grow at about one-third this rate.
The nail bed, the tissue under the nail plate, is made up of epithelium (the type of tissue that makes up the surface of most of the body) overlying a dermis very richly supplied with tiny blood vessels and resting on top of the bone. The dermis contains a huge network of sensory nerves. The nail matrix, which produces the nail, is continuous with the nail bed and extends beneath the proximal nail fold for about three-eighths inch. The cells of the nail matrix gradually move upward to form the nail plate, becoming keratinized—that is, toughened—as they do so.
Nails have several important functions. They protect the ends of the fingers and toes in a cosmetically pleasing way. The multiple sensory nerves in the dermis of the nail bed allow us to feel fine touch and pain, which is a protective mechanism. Nails are also important tools with which we can scratch and grasp and enhance other fine motor skills of the fingers and toes.
Now that we have examined how the skin, hair, and nails are put together and how they work, let us turn to the various ways in which these wonderful structures can be cared for and, should they develop problems or disorders, treated.
Excerpted from Smart Medicine for Your Skin by Jeanette Jacknin. Copyright © 2001 by Jeanette Jacknin, M.D.. Excerpted by permission. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
|How to Use This Book||xv|
|Part 1||The Elements Of Health Care For Your Skin|
|Understanding Your Skin, Hair, and Nails||7|
|Conventional Approaches to Skin Care||18|
|Diet and Nutrition||40|
|Acupuncture and Acupressure||80|
|Other Skin Therapies||86|
|Part 2||Common Skin Problems|
|Bites and Stings, Insect and Spider||130|
|Cuts and Scrapes||166|
|Poison Ivy, Oak, and Sumac||229|
|Scars and Keloids||263|
|Varicose Veins and Spider Veins||310|
|Part 3||Skin-Care Treatments And Techniques|
|Guided Imagery Techniques||344|
|Sound and Music Therapy||362|
Posted April 19, 2002
Well written, nicely organized, and highly informative, this comprehensive guide to skin problems and solutions is helpful and understandable to professionals and laypersons alike. Dr. Jacknin's clearly-written book provides a wealth of conventional and complementary treatment approaches in a straightforward and readable style. She offers down-to-earth information and suggestions that make sense. This book is both a comprehensive reference work and an interesting read.Was this review helpful? Yes NoThank you for your feedback. Report this reviewThank you, this review has been flagged.
Posted July 19, 2001
'Smart' is the word for this acurate, balanced dermatology guide that presents both traditional therapies and alternative medicine choices. Written for health care professionals, yet suitable for individuals who want to take charge of their own health, this is an excellent resource for skin care. Smart Medicine for Your Skin is immediately useful and accessible. As a family doctor, I refer to it frequently for conventional allopathic treatment modalities. What I like most however is that it gives me multiple alternative therapies that I can review with patients. The explanations are easy to understand and my patients like to have choices. As a bonus, the reference section provides in-depth resources for further explanations, classified by condition. This section also provides helpful listings of manufacturers, publishers and organizations all easily accessible within the framework of one book. It belongs on my bookshelf and I recommend it for yours. Harriet Schanzer, M.D.Was this review helpful? Yes NoThank you for your feedback. Report this reviewThank you, this review has been flagged.