CHAPTER 21 Nutrition and Digestion

1. CHAPTER 21Nutrition and Digestion Nutrition->life process by which an organism obtains and utilizes food

2. OBTAINING AND PROCESSING FOOD • Animals ingest their food in a variety of ways • Animal diets are highly varied • Herbivores are plant-eaters • Carnivores are meat-eaters • Omnivores eat both plants and other animals

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. HUMAN DIGESTIVE SYSTEM • consists of 1. alimentary canal (GI gastrointestinal tract) ~ continuous one way food tube (mouth to anus) 2.accessory glands ~pancreas, liver, & gallbladder

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

7. HUMAN DIGESTIVE SYSTEM • When food is swallowed, it is moved through the alimentary canal by peristalsis • Peristalsis is rhythmic muscle contraction in the walls of the digestive tract • Ringlike sphincter muscles regulate the passage of food

8. 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!

9. 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

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

11. The food and breathing passages both open into the pharynx • The swallowing reflex moves food from the pharynx into the esophagus • Food is now in the form of a bolus

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

13. The stomach mechanically churns food into liquid and further chemically digests some of the food by secreting gastric juice • The stomach mixes food with gastric juice: 1. water-solvent 2. mucus-lubrication 3. pepsin- enzyme that begins chemical digestion of protein 4. Hydrochloric acid ( HCl) - makes food acidic, (pH=2) activates pepsin Food now in liquid form –chyme NOT all digestion has occurred

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

15. 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

16. The small intestine is the major organ of chemical digestion and nutrient absorption • Alkaline pancreatic juice neutralizes stomach acids • Its enzymes digest polysaccharides, proteins, nucleic acids, and fats • Bileemulsifies fat droplets for attack by pancreatic enzymes • It is made in the liver and stored in the gall bladder

17. 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

18. 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

19. Enzymes from the walls of the small intestine complete the digestion of many nutrients

20. Absorption • The lining of the small intestine is folded and covered with tiny, fingerlike villi • Villi increase the absorptive surface • Nutrients pass through the epithelium of the villi and into the blood • The blood flows to the liver • The liver can store nutrients and convert them to other substances the body can use • Center of villi contains lymph vessel called lactealswhich absorb fatty acids

21. 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

22. The large intestine reclaims water • Undigested material passes to the large intestine, or colon • Water is absorbed • Feces are produced • Absorption of vitamins produced by bacteria that live in LI • Storage of feces Largeintestine(colon) Small intestine Endof smallintestine Rectum Anus Nutrientflow Cecum

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. 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