Gastrointestinal System

The gastrointestinal (GI) system has the critical task of supplying essential nutrients to fuel all the physiologic and pathophysiologic activities of the body. Its functioning profoundly affects the quality of life through its impact on overall health. The GI system has two major components: the alimentary canal, or GI tract, and the accessory organs. A malfunction anywhere in the system can produce far-reaching metabolic effects, eventually threatening life itself.

The alimentary canal is a hollow muscular tube that begins in the mouth and ends at the anus. It includes the oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine. Peristalsis propels the ingested material along the tract; sphincters prevent its reflux. Accessory glands and organs include the salivary glands, liver, biliary duct system (gallbladder and bile ducts), and pancreas.

Together, the GI tract and accessory organs serve two major functions: digestion (breaking down food and fluids into simple chemicals that can be absorbed into the bloodstream and transported throughout the body) and elimination of waste products from the body through defecation.

PATHOPHYSIOLOGIC CONCEPTS

Disorders of the GI system often manifest as vague, nonspecific complaints or problems that reflect disruption in one or more of the system's functions. For example, movement through the GI tract can be slowed, accelerated, or blocked, and secretion, absorption, or motility can be altered. As a result, one patient may present with several problems, the most common being anorexia, constipation, diarrhea, dysphagia, jaundice, nausea, and vomiting.

Anorexia

Anorexia is a loss of appetite or a lack of desire for food. Nausea, abdominal pain, and diarrhea may accompany it. Anorexia can result from dysfunction, such as cancer, heart disease, or renal disease, in the gastrointestinal system or other systems.

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