Digestive System | Biology for GCSE/IGCSE - Year 11 PDF Download

Identifying Organs of the Digestive System

Organs of the Digestive System: Function

Stages of food breakdown

Food enters the body and moves through 5 stages in the alimentary canal:

• Ingestion: The process of taking substances like food and drink into the body through the mouth.
• Mechanical Digestion: The breakdown of food into smaller pieces without changing the chemical composition of the food molecules. For example, chewing food in the mouth.
• Chemical Digestion: The breakdown of large, insoluble molecules into smaller, soluble molecules through chemical processes. An example is the action of enzymes in the stomach breaking down proteins.
• Absorption: The movement of small food molecules and ions through the intestinal wall into the bloodstream for distribution to cells and tissues. For instance, nutrients like glucose being absorbed into the blood from the small intestine.
• Assimilation: The process where digested food molecules are taken up by cells in the body to be used for energy or as building blocks for growth and repair. An example is amino acids from digested proteins being used to build muscle tissue.
• Egestion: The elimination of undigested or unabsorbed food material from the body in the form of feces through the anus. This includes indigestible parts of food like fiber.

Functions of the Digestive Organs Table