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Human Digestion and Absorption

Human Digestion and Absorption. Chapter 4. Organization of the Human Body. Chemical Level Atoms combine to form molecules Cell Level Molecules form organelles Use ATP Tissue Level Similar cells make up tissues. Organization of the Human Body. Organ Level

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Human Digestion and Absorption

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  1. Human Digestion and Absorption Chapter 4

  2. Organization of the Human Body • Chemical Level • Atoms combine to form molecules • Cell Level • Molecules form organelles • Use ATP • Tissue Level • Similar cells make up tissues

  3. Organization of the Human Body • Organ Level • Different tissues combine to form organs • Organ System Level • Organs make up an organ system • Organism Level • Organ systems make up an organism

  4. Digestive Organ System • GI tract • Mouth, esophagus, stomach, small intestine, large intestine • Accessory organs: Liver, pancreas and gall bladder

  5. Digestive Organ System

  6. Digestive System Overview • Digestion • Process of breaking down foods into a form the body can use • Absorption • Uptake of nutrients from the GI tract into the blood or lymph

  7. Anatomy of the GI Tract • GI tract • Long hollow muscular canal. Nutrients pass through the wall of the canal to be absorbed • Four layers (listed from inner most layer to outermost layer) • Mucosa • Submucosa • Muscle • Serosa

  8. GI Motility • Peristalsis • Contractions of the GI tract, mainly in esophagus, stomach, and small intestine • Segmentation • Back and forth movement-happens in small intestine so there is mixing with digestive juices • Mass movements • Slow peristalsis over widespread area- in large intestine to help propel fecal matter to rectum • Elimination

  9. One Way Street Sphincters: Ring like muscles along the GI tract that control the flow of contents

  10. Mouth (Oral Cavity) Chewing breaks up food and increases surface area. These smaller food particles are mixed with saliva and forms a bolus. Saliva • Lysozyme • Break down bacteria • Amylase • Break down starch • Mucus • Lubricate and hold bolus together

  11. Taste and Smell • Taste buds on the tongue and soft palate • Salty (from metal ions) • Sour (from acids) • Sweet (from organic compounds) • Bitter (many diverse compounds like phytochemicals) • Umami or savory (from amino acids) • Olfactory glands • Sense of smell (enhances sense of taste)

  12. Esophagus • Swallowing • Moves bolus from the mouth to the esophagus • Epiglottis • Prevents food from lodging in the trachea • Covers the larynx http://youtu.be/sM6uxd1uS6M

  13. Stomach • Bolus goes through lower esophageal sphincter into stomach • Mixed with stomach secretions becomes chyme • Pyloric sphincter allows chyme into the small intestine • Gastric inhibitory peptide (hormone) slows release of chyme into the small intestine to allow time for acid neutralization and digestion (only one teaspoon is allowed into the SI at a time).

  14. Stomach Secretions Chief cells produce: • Pepsinogen (an inactive protein-digesting enzyme) Other secretions include, Gastric lipase • Gastrin • Hormone stimulated when food is in stomach; controls release of HCl and pepsinogen and stimulates motility • Mucus • Protects the stomach from being digested

  15. Stomach Secretions Parietal cells produce hydrochloric acid which: • Inactivates proteins • Destroys bacteria and viruses • Aids in mineral absorption (dissolves them) • Converts pepsinogen (protein digesting enzyme) into pepsin (active form)

  16. Small Intestine Most digestion and absorption occurs here Sections: Duodenum, Jejunum Ileum

  17. Small Intestine • Villi (finger like projections on interior of SI) that are lined with: • Goblet cells make mucus • Endocrine cells produce hormones • Cells (enterocytes) that produce enzymes for absorption

  18. Hormones OF the Small Intestine • Gastrin • Also released by stomach, stimulates intestinal motility • Cholecystokinin (CCK) • Stimulated by dietary fat in chyme, stimulates release of pancreatic enzymes and bile • Secretin • Stimulated by acidic chyme, stimulates release of pancreatic bicarbonate • Gastric Inhibitory peptide • Stimulates stomach to limit gastric juices, slows motility

  19. Accessory Organs: Liver, Gallbladder and Pancreas • Liver • Provides bile • Needed to emulsify fat (disperse into droplets and suspend in water) so it can be absorbed • Gallbladder • Bile storage • Pancreas • Produces sodium bicarbonate, lipases, proteases and pancreatic amylase

  20. Accessory Organs: Liver, Gallbladder and Pancreas

  21. Large Intestine Functions: Absorption of water and electrolytes, house bacterial flora, and form and expel feces. • Colon • Cecum, ascending colon, transverse colon, descending colon and sigmoid colon • Rectum • Anus

  22. Large Intestine

  23. Absorption

  24. Absorption • Passive (fat, water, some minerals) • High concentration to low • Facilitated (ex. fructose) • High concentration to low + carrier protein • Active (amino acids, glucose) • Low concentration to higher + energy • Endocytosis (large proteins like immune factors) • Engulfment

  25. Absorption

  26. Moving Nutrients • Cardiovascular System • Includes heart, blood vessels and blood • Water-soluble nutrients transported via capillaries in villi to portal vein, which leads to liver • Allows liver to process nutrients before entering general circulation • Lymphatic System • Includes lymph • Fat-soluble nutrients and large particles transported via lacteals into the lymph vessels to thoracic duct, where it connects to the blood stream.

  27. Bacterial Flora • Beneficial bacterial flora • Controls pathogenic bacteria • Synthesize Vitamin K and Biotin • Aid lactose digestion and fermentation • Pro-biotic • Live bacteria • Pre-biotic • Non digestible carbohydrates that promote the growth of beneficial bacteria

  28. Putting it all together Be able to trace the pathway of food from when you first eat it until it is eliminated or absorbed Know the major function of each organ and if it secretes any major enzymes or hormones

  29. Digestion Gone Awry Heartburn and Gastroesphogeal reflux (GERD) Causes Overweight, alcohol, smoking, pregnancy Foods that increase reflux Citrus, caffeine, chocolate, fatty foods, spicy foods, onion, garlic and tomato based foods Medications include H2 blockers (blocks histamine formation) and proton pump inhibitors

  30. Digestion Gone Awry Heartburn and Gastroesphogeal reflux (GERD)

  31. Digestion Gone Awry Ulcers Causes: H pylori, alcohol, aspirin and smoking (not stress) Treatment: • Medications (abx, same as GERD) • Avoid foods that increase symptoms

  32. Digestion Gone Awry • Gallstones • Food Intolerances • Lactose, gluten, MSG • Intestinal Gas • Flatulence • Air and undigested CHO in large intestine

  33. Digestion Gone Awry

  34. Digestion Gone Awry • Constipation • Fiber, fluid and exercise • Laxative use (bulk, osmotic, stimulants, softeners, and lubricants) • Diarrhea • Replace fluid and electrolytes • Irritable bowel • Cause unknown, examine dietary factors • Hemorrhoids

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