54 3.1 Digestion at a Glance
Figure 3.11 The digestive tract, also known as the gastrointestinal tract, is a “tube within a tube”
A number of organs are involved in digestion, which collectively are referred to as the digestive system.
The organs that form the gastrointestinal tract (mouth, esophagus, stomach, small intestine, large intestine (aka colon), rectum, and anus) come into direct contact with the food or digestive content.
The journey through the gastrointestinal tract starts in the mouth and ends in the anus as shown below:
Mouth –> Esophagus –> Stomach –> Small Intestine –> Large Intestine –> Rectum –> Anus
In addition to the GI tract, there are digestion accessory organs (salivary glands, pancreas, gallbladder, and liver) that play an integral role in digestion. The accessory organs do not come directly in contact with food or digestive content.
There are a number of enzymes that are involved in digestion. We will go through each one in detail, but this table should help give an overview of which enzymes are active at each location of the GI tract.
Table 3.11 Digestive enzymes
| Location | Enzyme/Coenzyme |
| Mouth | Salivary amylase
Lingual lipase |
| Stomach | Pepsin
Gastric lipase |
| Small Intestine | Pancreatic alpha-amylase
Brush border disaccharidases Pancreatic lipase Colipase Phospholipase-A2 Cholesterol esterase Proteases Brush border peptidases |
References & Links
1. http://www.wpclipart.com/medical/anatomy/digestive/Digestive_system_diagram_page.png.html
2. http://commons.wikimedia.org/wiki/File:Digestivetract.gif
Video
Enzymes and Digestion – http://www.youtube.com/watch?v=bNMsNHqxszc