Anatomy and Physiology of the Bowel

In order to better understand care and maintenance of one’s eliminative system, it’s helpful to understand the basics of bowel anatomy and physiology, though one doesn’t need to be a bowel expert to improve one’s health. 

The bowel responds quite well to the laws of healthy living and one must be aware of these laws and follow them religiously in order to reap the rewards of health and freedom from disease.

The Small Intestine

When food has passed through the stomach by way of the mouth and esophagus, it enters the long, coiled tube called the small intestine where about 90% of the absorption into the bloodstream of all food elements takes place.  By the time it reaches the small intestine, food has been reduced by the action of chewing and digestive juices into a liquid known as chyme.

Digestion of carbohydrates starts in the mouth with saliva and continues in the stomach.  Proteins are broken down into short chains of amino acids in the stomach while further reduction takes place in the small intestine until the molecules can be properly assimilated and absorbed.

When chyme has been thoroughly mixed and reduced inside the stomach, the pyloric sphincter muscle valve opens and allows the food to enter into the uppermost portion of the small intestine known as the duodenum (where many ulcers originate).

In the duodenum, the first of three portions of the small intestine, the chyme is again thoroughly mixed by the contraction of the muscular walls.

The long and circular muscles of the intestinal walls are capable of performing three different types of movements, serving different purposes.  The tube of the small intestine is divided by the circular muscles which contract and segment food as it passes. 

Further contraction of the muscles between these segments occurs, making small segments, then the first set of muscles relax.  This action results in motion called rhythmic segmentation and takes place 12 to 16 times per minute.  As a result of these movements, the chyme is thoroughly mixed with digestive juices and the wave of contraction known as peristalsis flows from the duodenum through the jejunum, or middle portion of the small intestine all the way until the third and final portion is reached, the ileum.

Peristalsis is the motion caused by the rhythmic coordination of the muscles and propels the chyme through the small intestine.  Normal muscular activity of the intestine is not usually felt, although toxin-producing bacteria may cause violent and often painful spasms.  Diarrhea and vomiting are both reactions to irritation and inflammation of the stomach and bowel.