The small intestine is a long tube that’s about 1½ inches to 2 inches (about 3.5 to 5 centimeters) around, and it’s packed inside you beneath your stomach. If you stretched out an adult’s small intestine, it would be about 22 feet long (6.7 meters) — that’s like 22 notebooks lined up end to end, all in a row!
The small intestine breaks down the food mixture even more so your body can absorb all the vitamins, minerals, proteins, carbohydrates, and fats. The grilled chicken on your pizza is full of proteins — and a little fat — and the small intestine can help extract them with a little help from three friends: the pancreas, liver, and gallbladder.
At 3 or 4 inches around (about 7 to 10 centimeters), the large intestine is fatter than the small intestine and it’s almost the last stop on the digestive tract. Like the small intestine, it is packed into the body and would measure 5 feet (about 1.5 meters) long if you spread it out.
The large intestine has a tiny tube with a closed-end coming off it called the appendix. It’s part of the digestive tract, but it doesn’t seem to do anything, though it can cause big problems because it sometimes gets infected and needs to be removed.