Ear Infections

When Bobby's little brother was still a baby, he started having one ear infection after another. At first, he was too young to tell anyone when his ear hurt, but he would tug at the ear and cry.

Eating Disorders

Actress Tracy Gold appeared for six seasons in the television series Growing Pains. She had been diagnosed with anorexia at age 12, but went through psychotherapy and seemed fine for the next few years.

Ebola Fever

The Ebola virus belongs to the group of viruses called filoviruses, as do the Marburg and Reston viruses. Scientists first identified the Marburg virus in 1967, when it caused a small outbreak among sick monkeys brought from Africa to a medical laboratory in Marburg, Germany.


Elephantiasis was known to the early Greeks and Romans. It is a tropical or subtropical disease, occurring where many kinds of disease-carrying mosquitoes are found: South America, Cuba, Puerto Rico, West Indies, Africa, Spain, Turkey, Asia, Australia, and many South Pacific Islands.


The body's circulatory system is like a huge network of small roads and large interstate highways. It is important that blood continuously flow through the body to carry nutrients, oxygen, and other substances to cells and organs.


Air reaches the lungs through a series of ever-smaller tubes. First air passes through the trachea (TRAY-kee-a), which is the large windpipe from the throat down the neck.


Viruses and other microbes rarely get into the brain, but when they do, they can cause an inflammatory condition* called encephalitis (en-sef-a-LY-tis). Most cases of encephalitis are so mild that they are never identified.


The heart contains four chambers, each of which has a special function as the heart pumps blood through the body. The inner walls of these chambers are called the "endocardium" and are lined with small blood vessels and smooth muscle.


Endometriosis is a condition in which endometrial tissue grows outside the uterus. The endometrium (en-do-ME-tree-um) is the lining of the uterus (womb), which is the muscular organ in which a fetus develops during pregnancy.

Environmental Diseases


It happened at her birthday party. Eleven-year-old Erin was ready to blow out the candles on her cake when she suddenly released a loud cry and dropped to the carpet.

Fainting (Syncope)

One minute, U.S. Attorney General Janet Reno was sitting in church.


To people with farsightedness, the words on this page would seem blurry, unless they were wearing prescription (pre-SKRIP-shun) eyeglasses or contact lenses designed to correct the problem. But if they looked up from the page to read a sign across the room, they probably could read it easily.

Fetal Alcohol Syndrome

Sarah was always very quiet and never caused any trouble in elementary school, but she had few friends and never did fit in. Although she got fair grades, the teachers never knew how difficult the lessons were for her.


The body adjusts its temperature in much the same way that the thermostat in a house works. With a thermostat, people set the temperature they want, and the heating or cooling system clicks on until the inside of the house reaches the right temperature.

Fibrocystic Breast Disorder

It is estimated that more than half of all women will experience the breast changes that are known as fibrocystic breast disorder. The symptoms vary from person to person.


Fibromyalgia is a relatively new term for an old disorder. It means pain in the muscles and joints*.

Flat Feet

Flat feet can happen at any age, and babies are born with them. Babies have fatty pads in the soles of the foot and in front of the heel, which fills the arch and gives feet their flat appearance.

Food Poisoning

Robin and her friends squeezed every pleasure they could into the early days of September, milking summer vacation for all it was worth. The make-your-own-sundae party at Robin's was the best time they had all summer.

Fungal Infections

Bread mold and mushrooms are among the most familiar examples of fungi (FUN-ji), organisms that grow in an irregular mass without roots, stems, or leaves. Fungi feed on other organisms, living or dead, and play an important role in helping dead plants and animals decay.


The gallbladder is a small pear-shaped organ that sits under the liver on the right side of the abdomen. The gallbladder concentrates and stores a greenish-brown liquid called bile that is made by the liver.


Gangrene is a condition in which living tissue (skin, muscle, or bone) dies and decays. Gangrene most often affects the legs, feet, arms, and fingers, but it also can affect internal organs such as the intestine or gallbladder.