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 ...

Dizziness refers to feelings of lightheadedness, imbalance, or vertigo (the sensation that one’s surroundings are spinning or moving). A loss of balance or unsteadiness (disequilibrium) can be caused ...

We see and hear about hearts everywhere. A long time ago, people even thought that their emotions came from their hearts, maybe because the heart beats faster when a person is scared or excited. Now ...

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 ...

How Does the Brain Work? And How Does the Nervous System Work? How do you remember the way to your friend's house? Why do your eyes blink without you ever thinking about it? Where do dreams come from?

Is it Safe to Use Household Chemicals During Pregnancy? Some household cleaners and chemicals are safe to use during pregnancy while others are not. Chemicals like ammonia and chlorine might cause ...

Both the brain and the spinal cord are protected by bone: the brain by the bones of the skull, and the spinal cord by vertebrae, a set of ring-shaped bones. They're both cushioned by layers of ...

Smoking is one of the worst things you can do to your body. Yet every single day, some kids and teens start smoking. Why? There's more than just one answer. Some kids may start smoking just because ...

Many things can lead to hearing loss, but often, no cause is found. Hearing loss is more likely if a child: Some hearing problems come on gradually after birth or show up later in life. If you are ...

Sexually transmitted diseases (STDs) are infections spread from person to person during sex (vaginal, oral, or anal) or close sexual contact. STDs are also called sexually transmitted infections, or ...

Enteroviruses (en-teh-roe-VY-rus-sez) are a common cause of infection in people of all ages, with symptoms that can range from mild to serious. Most enterovirus infections happen in the summer and ...

What Is a Breath-Holding Spell? A breath holding spell is when a child holds their breath, usually after being angry, frustrated, startled, or in pain. Sometimes the breath holding leads to the child ...