The Digestive System/How it works

Introduction

Whenever you eat and drink, food travels through your digestive system for processing.  Your body absorbs nutrients and removes waste products via your digestive system.  As water is absorbed from your digestive system, the waste products become more solid and form stools or feces.  The stools are eventually eliminated from your body when you have a bowel movement.

Anatomy

When you eat, your tongue moves chewed food to the back of your throat.  When you swallow, the food moves into the opening of the esophagus.  Your esophagus is a tube that moves food from your throat to your stomach.  Muscles in your esophagus wall slowly squeeze the food toward your stomach. 

A ring of muscles is located at the bottom of the esophagus.  It is called the lower esophageal sphincter (LES).  The LES opens to allow food to enter the stomach.  The LES closes tightly after the food enters.  This prevents stomach contents and acids from backing up into the esophagus.  The esophagus does not secrete mucus and is not protected from stomach acids. 

The stomach secretes mucus to protect the lining of the stomach from the acids.  Your stomach produces acids to break down food for digestion.  Your stomach processes the food you eat into a liquid form.  The processed liquid travels from your stomach to your small intestine.

The small intestine is a tube that is about 20-22 feet long and 1 ½ to 2 inches around.  The duodenum is the first part of the small intestine.  It is a short C-shaped structure that extends off of the stomach.  The jejunum and the ileum are the middle and final sections of the small intestine.

Your gallbladder works with your liver and pancreas to send bile and digestive enzymes to the first part of your small intestine.  Your small intestine uses these digestive products to break down the liquid from your stomach even further so your body can absorb the nutrients from the food that you ate.  The remaining waste products from the small intestine travel to the large intestine.

Your large intestine, also called the large bowel or colon, is a tube that is about 5 feet long and 3 or 4 inches around.  The lower GI tract is divided into sections, including the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal, and anus.  The appendix is located on the cecum, but it does not serve a purpose in the digestive process. 
 
The first part of the colon absorbs water and nutrients from the waste products that come from the small intestine.  As the colon absorbs water from the waste product, the product becomes more solid and forms a stool.  The large intestine moves the stool into the sigmoid colon, where it may be stored before being traveling to the rectum.  The rectum is the final 6-inch section of your digestive tract.  No significant nutrient absorption occurs in the rectum or anal canal.  From the rectum, the stool moves through the anal canal.  It passes out of your body through your anus when you have a bowel movement.