When people talk about the calories in food, what do they mean? A calorie is a unit of measurement — but it doesn't measure weight or length. A calorie is a unit of energy. When you hear something ...

Scratch scratch. Scratch. Your head is feeling really itchy. Could it be lice? If so, you're not alone. Every year, millions of people worldwide get head lice. Most of those millions are kids. Any kid ...

How Does Air Enter the Respiratory System? Air enters the respiratory system through the nose or the mouth. If it goes in the nostrils (also called nares), the air is warmed and humidified. Tiny hairs ...

What Is the Digestive System? Food is our fuel, and its nutrients give our bodies' cells the energy and substances they need to work. But before food can do that, it must be digested into small pieces ...

The thyroid (say: THYE-royd) is a gland, which is an organ that makes special chemicals called hormones (say: HOR-moans). The thyroid is shaped like a little butterfly or bow tie and it sits under the ...

Parents might be surprised by how their newborn looks. Before birth, babies are immersed in amniotic fluid and folded up in an increasingly tight space. Then in most deliveries, they're pushed through ...

Head lice are tiny wingless insects. They live among human hairs and feed on blood from the scalp. Head lice are a common problem, especially for kids. They spread easily from person to person, and ...

How Do I Take a Rectal Temperature? The best way to take a temperature in infants and young children is by taking a rectal temperature. Don't worry — it's a simple and safe process.

What Is the Anterior Cruciate Ligament? The anterior cruciate ligament (ACL) is one of the ligaments in the knee joint. A ligament is a tough, flexible band of tissue that holds bones and cartilage ...

What Can I Do About Animal Bites and Scratches? Animal bites and scratches, even minor ones, can sometimes lead to problems. Whether the animal is a family pet (in kids, most animal bites that are ...

aerobic (say: air-OH-bik) activity: Aerobic activity is any kind of movement that makes your muscles use oxygen. It gets your heart pumping, too. Swimming, dancing, and soccer are all types of aerobic ...

It’s normal for people to masturbate (touch or rub their own genitals because they like the way it feels). Some people do it to relieve stress or tension. It’s nothing to be ashamed of or embarrassed ...