Digestive System

The Digestive System

The digestive system includes the digestive tract and its accessory organs, which process food into molecules that can be absorbed and utilized by the cells of the body. Food is broken down, bit by bit, until the molecules are small enough to be absorbed and the waste products are eliminated. The digestive tract, also called the alimentary canal or gastrointestinal (GI) tract, consists of a long continuous tube that extends from the mouth to the anus. It includes the mouth, pharynx, oesophagus, stomach, small intestine, and large intestine. The tongue and teeth are accessory structures located in the mouth. The salivary glands, liver, gallbladder, and pancreas are major accessory organs that have a role in digestion. These organs secrete fluids into the digestive tract.

Food undergoes four types of processes in the body:

Ingestion - Take in food through the mouth.
Digestion - Broken into smaller particles that can be acted upon by various enzymes
Absorption - Pass through cell membranes of the lining in the small intestine into the blood or lymph capillaries.
Elimination - The removal of indigestible wastes through the anus, in the form of faeces.

Regions of the Digestive System

At its simplest, the digestive system is a tube running from mouth to anus.

Digestive tract

Regions of the digestive system can be divided into two main parts: the alimentary tract and accessory organs. The alimentary tract of the digestive system is composed of the:

Mouth
Pharynx
Oesophagus
Stomach
Small and Large intestines
Rectum and Anus

Associated with the alimentary tract are the following accessory organs:

Salivary Glands
- It has a cleansing action on the teeth.
- It moistens and lubricates food during mastication and swallowing.
- It dissolves certain molecules so that food can be tasted.
Liver
- Bile production and excretion
- Excretion of bilirubin, cholesterol, hormones, and drugs
- Metabolism of fats, proteins, and carbohydrates
- Enzyme activation
- Storage of glycogen, vitamins, and minerals, and regulation of glucose levels
- Synthesis of plasma proteins, such as albumin, and clotting factors
- Blood detoxification and purification
- Conversion of ammonia, a by-product of metabolism, into a less toxic form called urea.
Gallbladder - Storage reservoir for bile
Pancreas
- Production of Insulin
- Production of Pancreatic juices

Common Digestive Problems

Haematemesis is the vomiting of fresh red blood or old darker blood often referred to as coffee grounds. The source is generally the upper gastrointestinal tract if the blood is fresh or from the stomach with the darker blood.

Peptic ulcer is a non-malignant ulcer of the stomach (called gastric ulcer) or duodenum (called duodenal ulcer).

Pancreatitis is an inflammation of the pancreas. It can occur periodically or chronically. The first sign may be a sudden, severe abdominal pain above the navel, which travels through to the back. Accompanying symptoms may include a slight fever, nausea, and vomiting.

Constipation is the term given for infrequent or difficult evacuation of small, hard stools, accompanied by mild abdominal discomfort. When the condition is chronic, it may include nausea, stomach rumbling, appetite loss, and malaise.

This list is not complete as there are many problems that can occur.

Management

Refer to the section Acute Abdominal Problems

Digestive System

A detailed picture of the digestive system. A new window will open, close to return to this page