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The digestivesystem and disorders


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Overview of the Digestive System as well as some common disorders.

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The digestivesystem and disorders

  1. 1. Human Digestion Overview
  2. 2. GI (gastrointestinal) tract = alimentary canal
  3. 3. Ingestion • Mouth – mechanical digestion • teeth – breaking up food – chemical digestion • saliva – Enzymes start breaking down molecules in food – Moistens and lubricates for easy swallowing
  4. 4. Pharynx • The back of the throat. • Larynx-passage for air, closes when we swallow.
  5. 5. Peristalsis • series of involuntary wave-like muscle contractions which move food along the digestive tract
  6. 6. Stomach • Food is temporarily stored here. • Gastric juices are secreted. • Has layers of muscle that line the inside. • Mechanically and chemically breaks down food.
  7. 7. Gastric Juices • Secreted by the stomach. • Acidic (pH 1.5-2.5) (HCl). • Pepsin- an enzyme that breaks down large proteins into amino acids. • Food is further broken down into a thin liquid called chyme.
  8. 8. Accessory Organs • Liver • Gall Bladder • Pancreas
  9. 9. Liver • Function – produces bile • bile stored in gallbladder until needed • breaks up fats
  10. 10. BILE • Bile emulsifies lipids (physically breaks apart FATS) • Bile is a bitter, greenish-yellow alkaline fluid, stored in the gallbladder between meals and upon eating is discharged into the duodenum where it aids the process of digestion.
  11. 11. Gall bladder • Pouch structure located near the liver which concentrates and stores bile • Bile duct – a long tube that carries BILE. The top half of the common bile duct is associated with the liver, while the bottom half of the common bile duct is associated with the pancreas, through which it passes on its way to the intestine.
  12. 12. Pancreas • An organ which secretes both digestive enzymes (exocrine) and hormones (endocrine) • ** Pancreatic juice digests all major nutrient types.
  13. 13. Small Intestine • Most chemical digestion takes place here. • Simple sugars and proteins are absorbed into the inner lining. • Fatty acids and glycerol go to lymphatic system. • Lined with villi, which increase surface area for absorption, one cell thick.
  14. 14. Small intestine • Function – chemical digestion • major organ of digestion & absorption – absorption through lining • over 6 meters! • small intestine has huge surface area = 300m2 (~size of tennis court) • Structure – 3 sections • duodenum = most digestion • jejunum = absorption of nutrients & water • ileum = absorption of nutrients & water
  15. 15. Duodenum • 1st section of small intestines – acid food from stomach – mixes with digestive juices from:  pancreas  liver  gall bladder
  16. 16. Absorption in the SI • Much absorption is thought to occur directly through the wall without the need for special adaptations • Almost 90% of our daily fluid intake is absorbed in the small intestine. • Villi and microvilli - increase the surface area of the small intestines, thus providing better absorption of materials
  17. 17. Large intestines (colon) • Function – re-absorb water • use ~9 liters of water every day in digestive juices • > 90% of water reabsorbed – not enough water absorbed » diarrhea – too much water absorbed » constipation
  18. 18. Large Intestine • Solid materials pass through the large intestine. • These are indigestible solids (fibers). • Water is absorbed. • Vitamins K and B are reabsorbed with the water. • Rectum- solid wastes exit the body.
  19. 19. You’ve got help! • Living in the large intestine is a community of helpful bacteria – Escherichia coli (E. coli) • produce vitamins – vitamin K; B vitamins • generate gases – by-product of bacterial metabolism – methane, hydrogen sulfide
  20. 20. Digestive Disorders Most of the time, the digestive system works very effectively. However, there are some things that can happen to cause disruptions.
  21. 21. Digestive Disorders • Ulcer – erosion of the surface of the alimentary canal generally associated with some kind of irritant – Can be caused by bacteria – Excessive stomach acid – Some medications
  22. 22. Digestive Disorders • Heartburn – Acid from the stomach backs up into the esophagus. – If the sphincter muscles at the top of the stomach do not seal tightly enough, stomach acid can move up the esophagus and cause a burning sensation. – Can erode the esophagus if not treated
  23. 23. Digestive Disorders • Food Poisoning – Bacteria, viruses, parasites, or toxins in food cause digestive upset – Onset of symptoms can be from 4 hours to 28 days. – Prevention is important, including cooking all foods thoroughly and maintaining cleanliness in all cooking and processing areas. – Symptoms: nausea, vomiting, diarrhea, fever, aches, cramps, and sometimes death.
  24. 24. Digestive Disorders • Constipation – a condition in which it becomes difficult to empty the large intestine. – too much water is reabsorbed – solid waste hardens
  25. 25. Digestive Disorders • Diarrhea – a when things move through the intestine quickly and not much water is absorbed. – This results in increased, multiple, watery feces. – This condition may result in severe dehydration, especially in infants
  26. 26. Appendix Vestigial organ
  27. 27. Digestive Disorders • Appendicitis – an inflammation of the appendix due to infection – The appendix is blocked and swells in response. – Common treatment is removal of the appendix via surgery
  28. 28. Digestive Disorders • Gallstones – an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder – Can either be “passed” (OUCH!!) or surgically removed
  29. 29. Digestive Disorders -- Eating Disorders • Anorexia Nervosa – a psychological condition where an individual thinks they appear overweight and refuses to eat. • Bulimia – condition where individual forces themselves to vomit after eating as a weight-loss method – Damages teeth and esophagus