Heart: The heart is a muscle that pumps blood throughout the body. It is located in the chest, just behind the breastbone. The heart is about the size of a fist. It beats about 100,000 times per day. Brain: The brain is the control center of the body. It is located in the skull. The brain is about the size of a grapefruit. It contains about 100 billion neurons. Neurons are cells that send and receive messages. The brain controls everything we do, including thinking, feeling, and moving. Lungs: The lungs are organs that allow us to breathe. They are located in the chest, on either side of the heart. The lungs are about the size of a football. They are made up of millions of tiny air sacs. The air sacs allow oxygen to enter the blood and carbon dioxide to leave the blood. Stomach: The stomach is an organ that helps us digest food. It is located in the upper abdomen. The stomach is about the size of a grapefruit. It can hold about 1 quart of food. The stomach breaks down food with a...