Anatomy of the Skin (Magill’s Medical Guide, Sixth Edition)
The skin is the largest organ of the body. It provides a barrier between the external world and the internal world: It protects against external contamination and helps to maintain the sterility of the internal body. The skin also assists in temperature regulation; humans can survive only within a narrow temperature range. The skin has nerve receptors that supply the brain with information, providing an interface with the world. There are specialized receptors for touch, temperature, vibration, and position in space (proprioception).
Appendages to the skin are fingernails, toenails, and hair. They are mainly of psychological importance. Nails protect the tips of fingers and toes in humans but are not needed for protection as claws are in lower animals. Hair is analogous to feathers. In birds, tiny muscles attached to the base of each feather cause them to be ruffled; this creates air pockets and allows birds to conserve heat and keep warm. The same muscles persist in humans, causing “goose flesh,” but they do not serve any other function. The main importance of these appendages is cosmetic. For example, people spend billions of dollars on hair care products each year. The motivation for this activity is psychological.
The two main layers in skin are the epidermis and dermis. The epidermis is the upper or outermost layer, and cells are continually formed at its base. As new cells are formed, existing cells are...
(The entire section is 666 words.)
Complications and Disorders (Magill’s Medical Guide, Sixth Edition)
When normal skin anatomy and physiology are upset, several common diseases or disorders result. When the barrier provided by the skin is broken, bacteria, viruses, fungi, and other pathogens can invade the body, leading to infections. Locally, these infections can cause inflammation (redness and pain) of the skin; if widespread, they can lead to systemic infections. When the cells and other substances found in the skin become irregular or are abnormal, skin disorders or conditions result.
Skin disorders and conditions. Pigmentation of the skin results from the presence of melanocytes, cells that manufacture and contain melanin. Most humans have pigmentation over their entire bodies; the degree of pigmentation varies with different racial and ethnic groups. Local areas of increased color have a range of names depending on the size of the pigmented area. A freckle is small and discrete. A nevus is a larger area of hyperpigmentation. These conditions are attributable to underlying variations in the distribution of melanocytes. They are genetic in origin and permanent; they are also accentuated by exposure to sunlight. Melasmas are irregular, flat, light brown areas on the neck, cheeks, or forehead. They are caused by hormonal changes associated with pregnancy or contraceptive pills and by exposure to sunlight. Melasmas fade with the reduction of excess hormones. There are also color changes in the labia of...
(The entire section is 1676 words.)
For Further Information: (Magill’s Medical Guide, Sixth Edition)
Burns, Tony, et al., eds. Rook’s Textbook of Dermatology. 7th ed. Malden, Mass.: Blackwell Science, 2004. This is a core text in dermatology that will appeal to professionals and members of the general public who want a concise introduction to the subject. The aim of the book is to integrate basic science with clinical practice.
Frankel, David H., ed. Field Guide to Clinical Dermatology. 2d ed. Philadelphia: Lippincott Williams & Wilkins, 2006. Frankel, a noted internist and dermatologist, has enlisted widely respected and talented colleagues to help in the production of this book. It is a uniquely organized and easily readable field guide complete with 220 pages of excellent color illustrations.
Freinkel, Ruth K., and David T. Woodley, eds. Biology of the Skin. New York: Parthenon, 2001. Covers the basic biology of the skin, how the skin functions, effects of the environment, the molecules that direct cutaneous function, genetic influences, and methods in cutaneous research.
Goldsmith, Lowell A., Gerald S. Lazarus, and Michael D. Tharp. Adult and Pediatric Dermatology: A Color Guide to Diagnosis and Treatment. Philadelphia: F. A. Davis, 1997. This book provides excellent pictures to accompany good descriptions of dermatologic diseases.
Grob, J. J., et al., eds. Epidemiology, Causes, and Prevention of Skin Diseases. Cambridge, Mass.: Blackwell...
(The entire section is 366 words.)