Introduction
The purpose of this chapter is to
Identify the anatomical components of the digestive system as well as their functions
Discuss neural control of the digestive system
Compare and contrast mechanical and chemical digestion
Discuss the effects of again and disease on the digestive system
The GI tract is long tube that is open at both ends for the transit of food during processing
Named portions of the tube include the esophagus, stomach, small intestine, large intestine, and rectum
Accessory structures are not part of the GI tract, but they do contribute to food processing
Accessory structures include the teeth, tongue, salivary glands, liver, gall bladder, and pancreas
Digestive Processes
There are 6 basic processes involved in digestion The Digestive System
The GI tract, and accessory organs like the liver and pancreas, are responsible for facilitating the body’s metabolic processes.
Catabolism: Larger molecules are broken into smaller molecules (mouth, stomach, duodenum).
In the GI tract, this is called digestion and can occur by either mechanical or chemical means.
Anabolism: Smaller molecules are used as building blocks for larger molecules (liver). The Digestive System
Mechanical digestion includes all movements that facilitate catabolic processes:
Mastication
Swallowing
Mixing
Increase contact of food with digestive chemicals
Peristalsis
Movement of muscles within the GI tract that facilitates movement of food The Digestive System
Chemical digestion is mainly accomplished by using water (and enzymes) to break chemical bonds (hydrolysis).
Fats are broken down into fatty acids and glycerol.
Carbohydrates are broken down from polysaccharides into monosaccharides.
Proteins are broken down into polypeptides and amino acids.

Layers of the GI Tract
The wall of the GI tract from the lower esophagus to the