Long and coiled
Your small intestine is a long tube that starts at the bottom of your stomach. It's coiled up in the middle of your belly, like a garden hose.
In a grown-up, if you could stretch it all out, it would be about 20 feet long. That's longer than a car!
So why is it called small? Because it's narrow, only about an inch wide. The large intestine is much shorter but wider.
Three parts
The small intestine has three parts with funny names. The first, short part is the duodenum (doo-uh-DEE-num). Juices from the pancreas and bile from the gallbladder pour in here.
The middle part is the jejunum (jih-JOO-num), and the last part is the ileum (IL-ee-um). Most of the soaking up of food happens along these two.
Muscles in the walls squeeze in waves to push food slowly along, just like in your food pipe. Food spends a few hours in here.
Where food gets into your blood
By the time food reaches the small intestine, it's already a soupy mix. Here, juices finish breaking it into the tiniest pieces: sugars, building blocks of protein, and bits of fat.
These tiny pieces are nutrients (NOO-tree-ents). They're what your body uses for energy, for growing and for fixing itself.
Most nutrients pass through the walls of the small intestine into your blood. Your blood takes them to the liver first, and then all over your body.
Villi, the tiny fingers
The inside of your small intestine isn't smooth. It's covered with millions of tiny bumps called villi (VIL-eye), like the soft loops on a fluffy towel.
Each villus is covered with even tinier bumps. All these folds and fingers make a huge surface, so lots of food can be soaked up fast.
Think about drying off after a bath. A fluffy towel soaks up much more water than a smooth plastic sheet, because of all its little loops. Your small intestine uses the same trick.
Fresh and on guard
The lining of your small intestine works so hard that it's replaced every few days, so it always has fresh cells.
Its walls also have special patches that watch for germs in your food. They're part of your immune system, the team that keeps you healthy.