The Digestive System

Overview The organs and glands in the body that are responsible for digestion (the breakdown of large food molecules into simpler compounds) Begins with the mouth and extends through the esophagus, stomach, small intestine, and large intestine, ending with the rectum and anus

The Mouth Place where food enters the body Two types of digestion occurs: mechanical and chemical Mechanical digestions, or mastication, is the physical chewing and breaking up of food Chemical digestion uses enzymes in saliva (salivary amylase) to breakdown starch into maltose Once chewed the food moves through the pharynx into the esophagus in a wavelike motion known as peristalsis

The Stomach Several functions: temporarily stores ingested food, partially digests proteins, and kills bacteria Secretes gastric juices which contain enzymes and hydrochloric acid(HCL) Pepsin is one enzyme made that breaks down proteins into smaller peptides HCL lowers pH of the stomach making it an acidic environment Secretion of mucus protects the stomach lining Food is mechanically broken down by churning in the stomach This partially digested food, or chyme, is now ready for the small intestines

The Small Intestine Three regions: duodenum, jejunum, and ileum Chyme moves into the small intestine through the pyloric sphincter The walls secrete enzymes that break down all three food groups Digestive juices from the pancreas, liver, and gallbladder along with the enzymes Bile is a substance made from the liver that breaks down fats and other lipids Most of the absorption of nutrients happens through large folds in the walls called villi

The Large Intestine Large intestine includes colon, cecum, and rectum Colon is the junction of small and large intestines; major function is to absorb water from digestion Cecum is important in fermenting ingested material (mainly plant material) Feces moves through large intestine by peristalsis Too little water absorbed by the colon results in diarrhea and too much results in constipation Mostly harmless bacteria live in the colon and give off gasses that have offensive odors; these are expelled through the anus Feces is stored in the rectum

The Anus Two sphincters lie between the rectum and the anus The inner one is involuntary and the outer one is voluntary Periodically strong contractions of the colon create an urge to defecate feces through the anus

Presentation by: Brantley West and Katie Norflus