Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link
Quick Facts

Small Intestine

By

The Manual's Editorial Staff

Last full review/revision May 2021| Content last modified May 2021
Click here for the Professional Version
Get the full details
Topic Resources

Your digestive system breaks food down into separate nutrients that fuel your body.

Your digestive tract (also called the gastrointestinal or GI tract) is the hollow tube that food goes through when you swallow it, digest it, and then pass the waste products as stool.

What is the small intestine?

Your small intestine, also called the small bowel, is part of your digestive tract. It connects your stomach and large intestine. Most nutrients are absorbed through your small intestine.

Your small intestine has three parts:

  • Duodenum

  • Jejunum

  • Ileum

The duodenum is the first part of your small intestine and is connected to your stomach. Food and liquid leave your stomach and go into your duodenum to continue being digested. Digestive juices from your pancreas and bile (a green fluid that helps digest fat) from your gallbladder come into your duodenum through small tubes called ducts. These juices help break down food and also neutralize stomach acid. The walls of the small intestine make chemicals called enzymes that also help digest food.

The jejunum and ileum are the 2nd and 3rd parts of the small intestine. They absorb nutrients.

The walls of the small intestine are lined with muscles that contract to push food along.

Locating the Small Intestine

Locating the Small Intestine
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Test your knowledge

Non-Hodgkin Lymphomas
Non-Hodgkin lymphomas are a group of cancers that develop in white blood cells known as lymphocytes. Although there are more than 50 different disorders that can be called non-Hodgkin lymphoma, doctors sometimes group them into two broad categories: indolent lymphomas and aggressive lymphomas. Which of the following is characteristic of aggressive non-Hodgkin lymphomas? 
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
TOP