Human Digestion -Ch. 21.1

1. Human Digestion -Ch. 21.1 Section Objectives: Interpret the different functions of the digestive system organs. Outline the pathway food follows through the digestive tract. Identify the role of enzymes in chemical digestion.

2. Human Digestion • This part of the life process of NUTRITION-> process by which an organism obtains and utilizes food

3. Overview: Food processing occurs in four stages • Ingestion: taking in food • Digestion: mechanical and chemical breakdown of food so that it can be absorbed by the cells • Absorption: cells lining the digestive tract take up (absorb) small nutrient molecules • Elimination: undigested material passes out of the digestive tract

4. Human Digestion~ a 2 part process that changes food into a form useable by the body cells • 1. Mechanical digestion – physical breakdown of large pieces of food into smaller ones • 2. Chemical digestion – hydrolysis – the splitting of large insoluble molecules in small, soluble molecules with the use of water and enzymes ( in other words; breaking complex molecules into simple ones) The process of chemical digestion ( hydrolysis) is regulated by enzymes

5. Examples of chemical Digestion: • 1. Carbohydrates+ water -> simple sugars (glucose for instance) • 2. Proteins+ water -> amino acids • 3. Lipids+ water -> 3 fatty acids +gylcerol

6. HUMAN DIGESTIVE SYSTEM • Human digestive tract = GI (gastrointestinal) Consists of a continuous one way food tube (mouth to anus)

7. Mouth • Functions • mechanical digestion • teeth • break up food • chemical digestion (saliva) • amylase enzyme • digests starch • mucus • protects soft lining of digestive system • lubricates food for easier swallowing • buffers • neutralizes acid to prevent tooth decay • anti-bacterial chemicals • kill bacteria that enter mouth with food All thatin spit!

8. HUMAN DIGESTIVE SYSTEM • 1. Mouth: (oral cavity) ingests food • 2. Teeth: function in mechanical breakdown of food, increases surface area of food for enzyme action • 3.Tongue: acts as a plunger to push food back into the throat (pharynx) taste buds are located on the surface of the tongue

9. mouth break up food digest starch kill germs moisten food

10. HUMAN DIGESTIVE SYSTEM • 4. Pharynx: food is pushed by tongue to back of throat, initiates swallowing – food is now in the form of a bolus • Epiglottis: flap that prevents choking • 5. Esophagus: muscular tube that moves food from mouth to the stomach by process of peristalsis:wave of muscular contractions that moves chewed food to stomach

11. Swallowing (& not choking) • Epiglottis • flap of cartilage • closes trachea (windpipe) when swallowing • food travels down esophagus • Peristalsis • involuntary muscle contractions to move food along

12. Stomach • Functions • disinfect food • hydrochloric acid = pH 2 • kills bacteria • food storage • can stretch to fit ~2L food • digests protein • pepsin enzyme But the stomach is made out of protein! What stops the stomach from digesting itself? mucus secreted by stomach cells protects stomach lining

13. stomach kills germs break up food digest proteins store food mouth break up food digest starch kill germs moisten food sphincter sphincter

14. Ulcers Free of H. pylori Colonized by H. pylori • Used to think ulcers were caused by stress • tried to control with antacids • Now know ulcers caused by bacterial infection of stomach • H. pylori bacteria • now cure with antibiotics inflammation of stomach inflammation of esophagus H. pylori cell damaging proteins (VacA) inflammatory proteins (CagA)   cytokines helper T cells neutrophil cells white blood cells

15. Small intestine • Functions • digestion • digest carbohydrates • amylase from pancreas • digest proteins • trypsin & chymotrypsin from pancreas • digest lipids (fats) • bile from liver & lipase from pancreas • absorption • nutrients move into body cells by: • diffusion • active transport This iswhere all thework is done!

16. Absorption in Small Intestines • Absorption through villi & microvilli • finger-like projections • increases surface area for absorption SMALL INTESTINES6 meters long,but can stretchto cover a tennis court

17. small intestines breakdown food - proteins - starch - fats absorb nutrients mouth break up food digest starch kill germs moisten food stomach kills germs break up food digest proteins store food liver produces bile - stored in gall bladder break up fats pancreas produces enzymes to digest proteins & starch

18. Pancreas ~ accessory organ • Produces digestive enzymes • digest proteins • trypsin, chymotrypsin • digest starch • amylase • digest lipids • lipase • Buffers • neutralizes acid from stomach smallintestine pancreas

19. pancreas produces enzymes to digest all foods mouth break up food digest starch kill germs moisten food stomach kills germs break up food digest proteins store food

20. Liver & Gall Bladder ~accessory organs • Produces bile • breaks up fats • gallbladder only stores bile • that’s why you can have your gall bladder removed bile contains colors from old red blood cells collected in liver = iron in RBC rusts & makes feces brown

21. liver produces bile - stored in gall bladder break up fats mouth break up food digest starch kill germs moisten food stomach kills germs break up food digest proteins store food pancreas produces enzymes to digest proteins & starch

22. Large intestines (colon) • Function • re-absorbs water • use ~9 liters of water every day in digestive juices • if don’t reabsorb water would die of dehydration • > 90% of water re-absorbed • not enough water re-absorbed • diarrhea • can be fatal! • too much water re-absorbed • constipation • reabsorb by diffusion

23. You’ve got company! • Living in the large intestine is a community of helpful bacteria • Escherichiacoli:E.coli • digest cellulose • digests fruits & vegetables • produce vitamins • vitamin K & B vitamins • BUT generate gases • by-product of bacterial metabolism • methane, hydrogen sulfide • STINKY! PEE-YOO!

24. large intestines absorb water mouth break up food digest starch kill germs moisten food stomach kills germs break up food digest proteins store food liver produces bile - stored in gall bladder break up fats small intestines breakdown food - proteins - starch - fats absorb nutrients pancreas produces enzymes to digest proteins & carbs

25. Rectum • Last section of large intestines • eliminate feces through anus • what’s left over? • undigested materials • mainly cellulose from plants • called roughage or fiber • keeps everything moving & cleans out intestines • masses of bacteria So don’t forget to wash your hands!

26. Appendix Vestigial organ

27. SomeDigestive Homeostasis Disorders • 1.Constipation– person has uncomfortable or infrequent bowel movements results from sluggish peristalsis that allows excess water to be removed from feces (fecal matter hardens)- may result from insufficient fiber in diet • 2. Diarrhea– opposite of constipation– associated with intestinal disturbances caused by infections or stress– prolonged diarrhea may result in severe dehydration • 3. Gall stones– small hard particles made of cholesterol which form & collect in gall bladder- may block the bile duct and cause pain • 4. acid reflux -backflow of stomach contents upward into esophagus • 5. appendicitis- inflammation of appendix