Ask Doctor Cory.

Dear Dr. Cory:

Why do we have to have chickenpox? It is very boring, I've never had it before, Why is it called chickenpox? How can a person with chickenpox pass it on to a healthy person while standing next to them?

Anna Nishanian

Granada Hills, California

Dear Anna:

There are three theories about how chickenpox got its name. One theory is that the Old English word gican, meaning "to itch," is the source of the word "chicken" in chickenpox. A second theory is that the term "chickenpox" came about because the chickenpox skin rash/blisters look similar to the cicca pea. And a third theory is that the word "chicken" is sometimes used to describe weakness. So it might have been used to describe this milder form of pox, to separate it from the more serious disease of smallpox.

Chickenpox was first identified as a separate disease by William Heberden in 1767. Before this time, chickenpox was often confused with smallpox.

Because chickenpox is caused by a virus, it can be very contagious, or easily passed from person to person, just like cold viruses. Although a person might be healthy, if he or she has never had chickenpox before, it's very easy for the virus to infect the body.

People no longer have to have chickenpox now that a vaccine is available. If you have not had chickenpox before, you might want to talk to your doctor about getting the vaccine.

Dear Dr. Cory:

Why do we have liver in our bodies?

Melissa Brakke

St. Petersburg, Florida

Dear Melissa:

The liver is one of the most important and largest body organs. It has at least 5,000 functions that help to keep the body running smoothly.

Blood comes to the liver from the stomach, intestines, and the spleen. This blood has many nutrients in it to give the body energy and other materials that it needs. The liver breaks down these digested nutrients even further. It collects those that will be useful to the body and removes old cells from the blood. It stores and releases others such as glucose sugar, fats, iron, and vitamins, depending on the body's needs.

The liver also breaks down certain substances that may be poisonous or toxic to the body. It turns these toxins into harmless substances or sends them to the kidneys to be passed out of the body. This is called detoxification (de-tox-i-fi-CA-tion). Everything we eat, breathe, and absorb through the skin must be purified and detoxified by the liver.

Dear Dr. Cory:

Why isn't gas the same as air?

Megan Hill

Carrollton, Texas

Dear Megan:

Gas is any substance that is not a solid and not a liquid, like steam from a kettle. Air is a gas. But not all gases make air.

The air we breathe is actually a mixture of three different gases. It is mainly nitrogen (79 percent), with about 21 percent oxygen and 0.04 percent carbon dioxide.

Dear Dr. Cory:

What makes our blood red?

Lisa Harmon

Salisbury, Missouri

Dear Lisa:

Blood contains the substance hemoglobin. Hemoglobin contains iron. Iron is what gives the blood its red color. When the blood is low in oxygen, the hemoglobin is a purplish red color. When blood is full of oxygen, the hemoglobin is bright red.

Our bodies have two major types of blood vessels, or tubes that carry the blood through the body. One type, called arteries (AR-ter-eez), carries blood from the lungs and heart. This blood has lots of oxygen in it, so it is bright red. The other type of blood vessel is a vein (VAYN). Veins carry blood to the lungs and heart. This blood has very little oxygen in it, so it is more purplish red.