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CHAPTER 21 Nutrition and Digestion

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

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CHAPTER 21 Nutrition and Digestion

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

  5. 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 • sphincter muscles

  6. Digestion begins in the oral cavity • The teeth break up food (mechanical digestion) • Saliva moistens it • Salivary enzymes begin the hydrolysis of starch • The tongue pushes the chewed food into the (throat)

  7. The food and breathing passages both open into the pharynx • The swallowing reflex moves food from the pharynx into the esophagus • epiglottisis a flap that prevents choking • Food is now in the form of a …….

  8. The esophagus squeezes food along to the stomach • Peristalsis in the esophagus moves food boluses into the stomach

  9. 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. ? 2. ? For lubrication 3. ? enzyme that begins chemical digestion of protein 4. ? (pH=2) activates pepsin Food now in liquid form –chyme NOT all digestion has occurred

  10. Connection: Bacterial infections can cause ulcers • evidence suggests that a spiral-shaped prokaryote causes many ulcers • Helicobacter pylori growth erodes protective mucus and damages the stomach lining

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

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

  13. Absorption • The lining of the small intestine is folded and covered with tiny, fingerlike villi • 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

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

  15. SomeDigestive Homeostasis Disorders • 1. Constipation– person has uncomfortable or infrequent bowel movements results from sluggish peristalsis (fecal matter hardens)- some causes? • 2. Diarrhea– opposite of constipation– associated with intestinal disturbances caused by infections or stress • 3. Gall stones– small hard particles made of cholesterol which form- may block the bile duct and cause pain – collect where? • 4. acid reflux -backflow of stomach contents upward into esophagus • 5. appendicitis-

  16. NUTRITION • Overview: A healthful diet satisfies three needs • fuel for its activities • raw materials for making the body’s own molecules • essential nutrients that the body cannot make

  17. Chemical energy powers the body • Once nutrients are inside cells, they can be oxidized by cellular metabolism to generate energy • This energy is in the form of ATP

  18. Chemical energy powers the body • The energy a resting animal requires each day to stay alive is its basal metabolic rate (BMR)

  19. Chemical energy powers the body • More energy is required for an active life • Excess energy is stored as glycogen or fat

  20. A healthful diet • includes 13 vitamins • Most of these vitamins function as coenzymes • Essential minerals are required for many body functions • A sound diet supplies • enough raw materials to make all the macromolecules we need • the proper amounts of prefabricated essential nutrients • enough kilocalories to satisfy our energy needs

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