The Digestive System: A General Overview

The digestive system is responsible for the mechanical and chemical digestion of food products, for the absorption of nutrients, and the excretion of waste products. The proper functioning of the digestive system is necessary for proper nutrient absorption. Nutrients are critical to ensure overall good general health.

Mechanical Digestion

Mechanical digestion is comprised of two separate processes. The first is mastication, the process of chewing food mixed with salivary gland excretions. The second is a process known as peristalsis. Peristalsis is completed through smooth muscle contractions. These smooth muscle contractions are responsible for the movement of food throughout the digestive system.

Chemical Digestion

Chemical digestion is the process by which food products are chemically processed by the body. This is accomplished in several ways. The salivary glands excrete enzymes that begin the breakdown of food in the mouth. This is essential, as smaller particles are more easily digested throughout the rest of the digestive system. Hydrochloric acid, the only acid naturally produced by the body, contained with other gastric juices in the stomach further processes these food products. From here, the accessory organs are utilized. The pancreas produces enzymes, breaking the food products from complex to simple molecules. The liver produces bile and the gallbladder stores excess amounts.

Chemical Digestion: Accessory Organs

Chemical Digestion is not possible without the digestive system accessory organs. These accessory organs are responsible for the production and delivery of digestive enzymes. These accessory organs include:

• Pancreas: The pancreas is responsible for the production of the majority of digestive enzymes found in the stomach and duodenum (beginning portion of the small intestine.)
• Liver: The liver is responsible for the production and secretion of a substance known as bile, which aids in digestive absorption and proper excretion. The liver is also responsible for filtering the blood, which contains the absorbed nutrients.
• Gallbladder: The gallbladder is responsible for the storage of bile.

Chemical Digestion: Enzymes

Chemical digestion is completed through use of digestive enzymes. Currently, there are eight main digestive enzymes produced by the accessory organs, essential to proper digestion. These enzymes are primarily located in the stomach and small intestine, but can also be found in the mouth and large intestine. Each enzyme has special properties and a unique structure that allows it to complete its required functions.

• Elastase
• Collagenase
• Protease
• Lipase
• Nuclease
• Trypsin
• Chymotrypsin
• Amylase

How is the Digestive System Regulated?

Regulation of digestive system processes is hormonally controlled by the body. Specifically, there are three hormones that control digestive system processes.

• Secretin: Stimulates the liver for bile production, and stimulates the stomach to produce pepsin, an enzyme that is necessary for the proper digestion of proteins.
• Gastrin: Responsible for stimulating the need for acid production in the stomach. Regulates the growth of the mucosal stomach lining in the stomach and intestines.
• Cholecystokinin (CCK): Responsible for emptying the gallbladder, and for stimulation of pancreatic juice secretion.

Sources:

http://www.mayoclinic.com/health/digestive-system/AN00896

http://www.webmd.com/digestive-disorders/digestive-system