1. The Digestive System (sometimes referred to as the Gastro- intestinal system)

2. Major Functions of the Digestive System: Digestion (to process or breakdown food) Absorption (deliver nutrients to cells of the body)

3. The Digestive system is linked to many other systems: Nervous / Endocrine System (coordination, hormones, regulation) Circulatory System (O 2 and nutrient transport) Muscular and Skeletal System (provide structure)

4. Components of Digestion: INGESTION (motility) – the way food enters the mouth and moves through the digestive tract INGESTION (motility) – the way food enters the mouth and moves through the digestive tract DIGESTION and SECRETION – breakdown of food by physical means (peristalsis, contractions) or by chemical means (through the use of enzymes and HCl) DIGESTION and SECRETION – breakdown of food by physical means (peristalsis, contractions) or by chemical means (through the use of enzymes and HCl)

5. Components of Digestion (cont.): ABSORPTION – through villi in the small intestine (then enters the circulatory system) ABSORPTION – through villi in the small intestine (then enters the circulatory system) EGESTION – removal of unwanted and waste material EGESTION – removal of unwanted and waste material

6. Components of the Digestive Tract 1. MOUTH: teeth and tongue used for physical digestion (cut and chew food into a bolus) saliva (water and enzymes) used for easy sliding and chemical digestion (of carbohydrates in food)

7. Components of the Digestive Tract (cont.) 2. PHARYNX and EPIGLOTTIS: direct food bolus away from the trachea and down the… 3. ESOPHAGUS: long muscular tube lined with mucous to help bolus slide easily uses peristalsis (wave-like contractions) to push food downward

8. Components of the Digestive Tract (cont.) 4. STOMACH: located on left side of abdominal cavity (J- shaped) approx. size of fist but expands up to 1.5 L entrance/exit controlled by sphincter: - A) Cardiac Sphincter (connects to esophagus at top of stomach) - B) Pyloric Sphincter (connects to sm. intestine at bottom of stomach)

9. Components of the Digestive Tract (cont.) 4. STOMACH (cont.): muscles (wall) folds and contracts for physical digestion gastric juices (used for chemical digestion and protection) form acidic chyme (pH 2-3): - A) enzymes – renin, lipase, pepsin - B) hydrochloric acid – HCl - C) mucous initial site of protein (chemical) digestion

10. Components of the Digestive Tract (cont.) 5. SMALL INTESTINE: 2.5 cm wide and 7m long pH ranges from 12 to 9 to eventually 7 (neutral) Duodenum – first 1/3, major site of digestion (enzymes enter here) Jejunum – second 1/3, major site of absorption (through villi) I leum – some digestion and absorption

11. Components of the Digestive Tract (cont.) 5. SMALL INTESTINE (cont.): Villi: small finger-like projections (each villus is composed of micro-villi) that add surface area to increase absorption allows monosaccharides, amino acids, nutrients, etc into the capillary net (blood stream) allows lipids, fats, etc to pass into lacteal (lymph vessel) Digestion Ends Here ***

12. Components of the Digestive Tract (cont.) 6. LARGE INTESTINE: a.k.a. the colon 8cm wide and 1.5m long NO digestion here!! But: A) food absorption completed B) H 2 O re-absorption C) salt re-absorption D) make vitamin B and K (with help of bacteria) E) form and expel feces with help of cellulose (fiber) which provides bulk and triggers stretch receptors

13. Components of the Digestive Tract (cont.) 6. LARGE INTESTINE (cont.): largest part of lg. intestines is called the rectum (acts as a storage center) 7. Anus: sphincter for controlled release of waste

14. TOMORROW: Other Digestive Organs Enzymatic Digestion