Relating to the skin and especially to the dermis.

The word *dermal* often comes up nowadays in connection with cosmetic treatments. Dermal therapy usually means restoring moisture to dry, cracked skin. Dermal fillers such as collagen can be injected to fill in acne scars or reduce wrinkles. These have now been joined by treatments like Botox, which paralyzes facial dermal muscles, again in order to reduce wrinkles (since those dermal muscles are used to form expressions). A synonym for *dermal* is *cutaneous*.

The outer layer of the skin.

*Epidermis* includes the Greek prefix *epi-*, meaning “outer”; thus, the epidermis overlies the *dermis*, or inner layer of skin. The epidermis itself consists of four or five layers; the outermost layer is made of dead cells, which are being shed continuously. The epidermis acts as a physical barrier —a protective wrap over the body's surface, which, by preventing water loss, allows vertebrates to live on land.

One who prepares, stuffs, and mounts the skins of dead animals.

Taxidermists are called on not only by sportsmen and collectors but by museums, movie studios, and advertisers. Taxidermists first remove the skin (with its fur, hair, or feathers), then create a plaster cast of the carcass with which to produce a “mannequin,” on which they replace the skin. Producing trophies of lifelike quality that often recreate an exciting moment requires physical skill, attention to detail, and sometimes artistic talent.

Inflammation of the skin.

Dermatitis usually appears as a rash, and may cause itching, blisters, swelling, and often scabbing and scaling. It often marks an allergic reaction of some kind. *Contact dermatitis* is caused by something (often a chemical) touching the skin. *Atopic dermatitis* usually affects the insides of the elbows, the backs of the knees, and the face; generally resulting from an inherited sensitivity, it's often triggered by inhaling something. Eczema, psoriasis, and dandruff are all forms of dermatitis. Even in the worst cases, dermatitis isn't infectious and doesn't produce serious health consequences. ## ENDO **ENDO** comes from the Greek *endon*, meaning “within.” In English it appears almost always in scientific terms, especially in biology. A nonscientific *endo-* word is *endogamy*, meaning marriage within a specific group as required by custom or law—one of the many customs that can be seen everywhere from the most remote tribes to the highest society in wealthy countries.

(1) A hormone. (2) Any of several glands (such as the thyroid) that pour their secretions directly into the blood or lymph.

The body's glands remove specific substances from the blood and alter them for rerelease into the blood or removal. Glands such as those that produce saliva and sweat secrete their products through tiny ducts or tubes on or near the body's surface. The glands without ducts, called the *endocrine* glands, instead secrete their products into the bloodstream; the *endo-* root indicates that the secretions are internal rather than on the surface. The endocrine system includes such glands as the pituitary (which controls growth, regulates the other endocrines, and performs many other tasks), the thyroid (another growth gland that also influences metabolism), the adrenals (which secrete adrenaline and steroids), the hypothalamus (which influences sleep and weight regulation), and the ovaries (which produce eggs). Endocrine problems are treated by *endocrinologists*.

Relating to a branch of dentistry that deals with the pulp of the teeth.

*Endodontists*, as you might expect from the *endo-* root, deal with the interior of the tooth. The tooth's enamel, on the outside, covers a thick layer called the *dentin*; this in turn surrounds the innermost part, called the *pulp*, a mass of soft tissue through which nerves and blood vessels run. When a tooth has been badly damaged by decay or cracking, producing a risk of dangerous infection of the pulp, a “root canal” procedure is performed by an endodontist. Try to avoid ever getting to know an endodontist; brush your teeth twice daily, floss before bedtime, and never let a cavity go unfilled for long.

Developing or originating within a cell, organ, body, or system.

When biologists need to make a distinction between things that are produced within a cell or organ and things that affect it from the outside, they use the terms *endogenous* and *exogenous*. It used to be thought, for instance, that mutations in cells always resulted from exogenous causes, until it was discovered that substances in the body, including those called oxidants, could cause them *endogenously* as well. “Circadian rhythms”—the regular cycles, roughly 24 hours in length, that plants, animals, and humans rely on to regulate their days—are endogenously generated and don't actually depend on the sun for their timing.

Any of a group of proteins

Endorphins are the body's natural 'feel-good' chemicals, produced in the brain during exercise, excitement, pain, consumption of spicy food, love, and orgasm. The name comes from 'endogenous morphine'—morphine produced naturally within the body. These neurotransmitters interact with receptors in the brain that reduce perception of pain and trigger positive feelings, similar to the effects of morphine or other opioids, but without the harmful side effects or risk of addiction.