Glossary of Terms Amino Acids Key components in all living organisms from which proteins are made. There are 20 common amino acids.   Antibiotics Drugs prescribed to fight infectious diseases. These chemical substances can slow the growth of or kill other microorganisms, including beneficial microorganisms in the intestinal tract.   Chemotherapy A chemical treatment for disease, which has specific toxic effect on disease-producing microorganisms or that selectively destroys cancerous tissue.   Enteric Relates to the small and large intestines.   Epithelium The covering of the internal surfaces of the body, such as the lining of the gastrointestinal tract.   Gastrointestinal A term for the digestive tract, which consists of the esophogas, stomach, duodenum, small intestine, large intestine, and rectum.   Immune System The immune system consists of many organs and cells that defend the body against infection, disease, and foreign substances. The immune system can be stimulated in specific ways to fight specific health challenges.   Immunoglobulin A specialized protein produced by the body in response to challenge by a foreign molecule. Immunoglobulin is found mainly in serum and milk and serves to protect the body from microbial, viral, and fungal invasion.   Intestines The portion of the digestive tract where most nutrients are absorbed.   Serum A clear fluid from blood. Serum is rich in immunoglobulin and other nutrients that help support the tissues of the body.   Villi Tiny finger-like projections that cover the surface of the small intestine. Villi enhance the transport of fluids and nutrients from the intestinal lining.