The Chemical Digestion & Absorption of Food

The digestive system provides a way for nutrients to enter the circulatory system from the environment, according to Colorado State University. This cannot occur unless food is digested into extremely small molecules through mechanical and enzyme digestion. After food is digested into molecules that can be absorbed by the body, the epithelium lining absorbs simple sugars, amino acids and fats into the bloodstream.

Regulation

• The digestion system is regulated by hormones that are produced in the stomach, mucosa and small intestine, according to the National Digestive Diseases Information Clearinghouse. The primary hormones that help control digestion are gastrin, secretin and cholecystokinin. When gastrin is released it signals the stomach to produce acid that's used to break down food. Gastrin also plays a role in normal cell growth within the lining of the stomach, small intestine and the colon. Secretin causes the pancreas to create digestive juice that has high levels of bicarbonates. Bicarbonates aid the stomach in neutralizing acidic stomach contents before they reach the small intestine. Secretin also helps with the production of pepsin, and acts as a stimulant. Pepsin is an enzyme that helps the body digest different types of proteins. Pepsin also signals the liver to produce bile. The third main type of hormone involved with digestion is cholecystokinin, which stimulates the digestion of fats and proteins.

Absorption

• The main location that absorption of nutrients takes place is the small intestine, according to the Southern Illinois University School of Medicine. This plays a major role in the balance of electrolytes and water in the body. Electrolytes are essential minerals in the blood that carry an electric charge, according to Medline Plus, an online service of the National Library of Medicine and the National Institutes of Health. The small intestine contains muscle folds known as villi that help increase the surface area of the small intestine for absorption. Nutrients are absorbed through the villi and transferred directly into the bloodstream. The ileocecal valve is responsible for passing digested materials into the large intestine.

Pathway

• The digestive track starts in the esophagus, continues to the stomach, then the duodenum, the large intestine, small intestine, colon and eventually the anus, where it leaves the body, according to the National Digestive Diseases Information Clearinghouse.

Size

• The digestive track is approximately 30 feet long, according to Thinkquest.org.

Fun Fact

• Cows have three stomachs that help them digest food, according to Thinkquest.org. Food is cycled throughout the stomachs of a cow two to three times before it is released from the body. This means that the stomach of a cow is less efficient than the stomach of a human.