Stomach

Custom Search

Digestive System:

Digestive System Index

Colon

Digestion and Enzymes

Digestive System Overview

Duodenum

Esophagus

Gallbladder

Glands

Hormones

Large Intestine

Liver

Mouth

Mucosa

Nerves and the Digestive System

Nutrients

Pancreas

Peristalsis

Rectum and Anus

Saliva

Small Intestine

Spleen

Stomach

Teeth

Throat

Tongue

Digestive System Video Index

Human Body Index

Human Body Video Index

Science Videos


Science Main Index



 

The stomach is often what most people associate with the digestive system. It is a hollow, elastic-like, muscular sac located in the abdomen. It is connected between the esophagus and the duodenum. Food enters the stomach from the esophagus. Once in the stomach, gastric juices and muscular contractions break down the food preparing it for further processing in the small intestine. Read on to learn more about the stomach, and its role in digestion.

On this page:

Stomach

Top of Page

Stomach
The Stomach in the Abdomen

The stomach is the second phase of digestion. The first phase being the chewing food in the mouth. The stomach is located in the upper-left side of the abdomen, just below the diaphragm. The stomach is about 12 inches (30.5 cm) long and 6 inches (15.2 cm) wide with a capacity of about 1 qt (0.94 liters) in an adult.

The stomach is the second phase of digestion. The first phase being the chewing food in the mouth. The stomach is located in the upper-left side of the abdomen, just below the diaphragm. The stomach is about 12 inches (30.5 cm) long and 6 inches (15.2 cm) wide with a capacity of about 1 qt (0.94 liters) in an adult.

The stomach has three main areas. The fundus is the upper section of the stomach. The largest part of the stomach is the body. The lower end of the stomach is the pyloric antrum. The upper part of the stomach connects with the esophagus. The lower part of the stomach connects with the duodenum. The duodenum is the upper part of the small intestine.

Stomach
The Stomach

The wall of the stomach consists of several layers. The mucosa membrane is the inner-most layer. The mucosa produces enzymes and stomach acids used to kill bacteria and break down the food. Surrounding the mucosa is a muscle layer that produces contractions to mix and churn the food. The serosa provides the outer wrapping of the stomach.

When the stomach is empty, the muscle contracts and the mucosa creates distinct folds called rugal folds. When the stomach fills with food, the elastic muscle and rugal folds stretch allowing the stomach to expand.

Food enters the stomach from the esophagus. The esophageal sphincter, or valve, separates the stomach from the esophagus. This valve keeps food and gastric juices from returning back into the esophagus.

Once food is in the stomach, gastric juices begin to break down the food. The stomach produces several substances that assist in the digestion of food. Mucus is produced by the mucous cells of the mucosa. Mucus coats and lubricates the inner wall of the stomach, protecting it from acid and other chemicals. Hydrochloric acid, secreted from parietal cells, creates an acidic environment killing micro organisms such as bacteria. Pepsinogen is secreted by mucous cells and is responsible for digesting proteins.

Contractions of the stomach muscle, called peristaltic waves, grind, crush and mix the food producing a liquefied substance called "chyme." The pyloric sphincter separates the stomach from the duodenum. This valve keeps food and gastric juices in the stomach until liquefied enough to proceed into the duodenum. Each time a peristaltic wave reaches the pyloric sphincter, a small spurt of chyme is released into the duodenum. This process cycles until all of the food is liquefied in the stomach and proceeds to the duodenum.

The stomach and digestion process is controlled by both the Autonomic Nervous System and hormonal signals. These signals can both stop or increase the production of gastric juices and muscle contractions. For example, the hormone gastrin controls the production of acid and gastric juices.

Although the stomach breaks down the food, it actually absorbs very little of the food's nutrients. The nutrients move into the small intestine for absorption.

 

Books on the Stomach

Top of Page

   
   

 

Other links on the Stomach

Top of Page

   
 

Top of Page

 

 
Copyright © 1998-2012 Kidport