Know Your Gastrointestinal Tract

Terms You Should Know

• Absorption: The process of passing of nutrients from the intestine into the blood stream. 

• Anus: Opening at the end of the rectum that allows solid waste to be eliminated

• Colon: The large intestine.

• Digestion: The process of breaking down of food into its simple chemical compounds so that it can be absorbed.

• Duodenum: The first portion of the small intestine.

• Ileum: The last portion of the small intestine that connects to the large intestine. 

• Immune System: The body's natural defense system that fights disease. 

• Inflammation: A response to tissue injury that causes redness, swelling, and pain.

• Jejunum: The middle portion of the small intestine. 

• Large Intestine: Also known as the colon. 

• Rectum: Lowest portion of the colon. 

• Small Intestine: The organ that connects the stomach to the large intestine and absorbs nutrients. 

The gastrointestinal tract (GIT) is a highly specialized organ system that allows us to consume a variety of foodstuffs to meet our nutrient needs. It is in the GIT that food is converted into compounds that can be absorbed by the body. 
The digestive system is a series of hollow organs from the mouth to the anus. The walls of these hollow organs are composed of muscles arranged in layers that propel the contents by peristalsis ( in waves) away from the mouth. The digestive tract is lined by a tissue known as mucosa. In the mouth, stomach and small intestine, the mucosa contains tiny glands that produce juices which help in digesting the fold. Liver, gall bladder and the pancreas are the organs which are connected to the digestive tract. These organs produce digestive juices that flow through small tubes (ducts) into the small intestine. The faecal matter is stored in the colon (large intestine), so that its elimination can occur at a convenient time and in a convenient form. 

The digestive system is connected to the vascular, lymphatic and nervous systems to facilitate regulation of the digestive response, delivery of absorbed compounds to the organs of the body and the regulation of food intake. A primary function of the GIT is to extract nutrients from the complex mixture of foods that are consumed. The GIT also metabolises and eliminates the non-nutrient and toxic compounds present in the food. 
The GIT breaks down food into absorbable compounds through mechanical and biochemical processes. Chewing breaks food into smaller particles so that it can mix more readily with the digestive juices. The saliva lubricates the food bolus so that it passes readily through the oesophagus into the stomach and contains digestive enzymes. Swallowing moves the bolus of food into the stomach via the food pipe or the oesophagus. Movements of the stomach help mix the food with the gastric juices which, contain acid and digestive enzymes. The action of the stomach also breaks down food into smaller particles before sending it to the intestine. 

Digestion of macronutrients, which begins in the mouth continues in the small intestine. Here, the peristaltic motor activity propels the food along the length of the intestine and promotes mixing of food with pancreatic enzymes and bile acids. 

Approximately 10 12 microorganisms reside in the GIT, most of which are in the large intestine. Some of these microbes are considered harmful and are associated with intestinal diseases, while others are considered beneficial and are associated with the synthesis of vitamins, facilitating mineral absorption and immune stimulation. All digested food molecules are absorbed by the GIT, mostly from the small intestine (duodenum, jejunum and ileum). After the food molecules are absorbed, they are carried via the blood to the liver for further processing. It then distributes the nutrients throughout the body via the blood. 

Organs Associated with the Digestive Tract
Symptoms of Digestive Disorders