Digestion

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Digestion

  1. 1. Sections 16.2 and 16.3 Digestive System
  2. 2. <ul><li>The Digestive System has 3 functions: </li></ul><ul><li>Break down food into molecules the body can use </li></ul><ul><li>Absorb molecules into the blood </li></ul><ul><li>Eliminate waste </li></ul>
  3. 3. <ul><li>There are 2 types of digestion: </li></ul><ul><li>Mechanical Digestion - physically breaks food into smaller pieces (chewing and churning of the stomach) </li></ul><ul><li>Chemical Digestion - chemicals produced by the body break food into their smaller building blocks </li></ul>
  4. 4. Absorption is when the nutrients pass through the wall of the digestive system into the blood. Elimination is when what is not absorbed, such as fiber, becomes a waste that is removed from the body. Absorption vs. Elimination:
  5. 5. The Digestive system is 9 meters long!!!
  6. 6. Saliva is produced for both chemical AND mechanical digestion. Saliva:
  7. 7. Teeth are used for mechanical digestion Incisors (center teeth) – cut food into bite sized pieces Canines (pointy teeth) – tear and slash food Molars (back flat teeth) – crush and grind food
  8. 8. Food moves into esophagus from mouth Epiglottis covers trachea when you swallow (you can feel this happen with your finger on your throat as you swallow) Swallowing:
  9. 9. Esophagus is a muscular tube that connects the mouth and stomach. Covered in mucus to help food slid down It is 25 cm long, and food only remains here for about 10 seconds. Food is moved through it by muscular contractions called peristalsis . Esophagus:
  10. 10. You really can swallow upside down! 
  11. 11. Food is now in the stomach… <ul><li>The stomach holds about 2 liters of food. </li></ul><ul><li>Function : </li></ul><ul><li>to store the food you've eaten </li></ul><ul><li>to break down the food into a liquidy mixture </li></ul><ul><li>to slowly empty that liquidy mixture (chyme) into the small intestine </li></ul>
  12. 12. Digestive chemicals in the stomach include the enzyme pepsin (breaks down proteins) and hydrochloric acid (kills bacteria), and mucus (protects lining of stomach from acid). After 4 hours churning (peristalsis) in the stomach, the food has been changed into a thin, watery liquid called chyme . Digestive Juices:
  13. 13. What is the cause of acid reflux or heart burn.
  14. 14. Onto the small intestine… Most of the chemical digestion and absorption happens here. This organ is approx. 6 meters long (it is named “small” because of its diameter, 2-3 cm wide) Chyme mixes with enzymes already in the small intestine, and delivered from the liver and pancreas through tiny tubes attached to small intestine
  15. 15. <<<LIVER NOT IN DIGESTIVE TRACT>>> Liver produces bile for digestion of fats (does other things too) Bile flows from the liver and is stored in the gallbladder (sort of like a vacuole) After you eat, bile from the gallbladder goes into the small intestine Liver is the largest and heaviest organ inside the body!
  16. 16. Love Your Liver After blood moves through the digestive system, the nutrient-rich blood comes directly to the liver for processing. The liver filters out harmful substances or wastes, turning some of the waste into more bile. The liver even helps figure out how many nutrients will go to the rest of the body, and how many will stay behind in storage. The liver stores vitamins and glucose.
  17. 17. <<<Pancreas Not in the Digestive Tract>>> The pancreas helps digestion by producing enzymes that chemically break down starch, protein, and fat. It also secretes insulin, a hormone the regulates the levels of glucose in the blood.
  18. 19. Back to the small intestine… Inside of small intestines contain villi (fingers), have a large surface area absorption of nutrients can happen fast Villi are where nutrient absorption into blood takes place. Capillaries inside the millions of villi are where nutrient exchange takes place into the blood stream.
  19. 20. These are villi magnified with an electron microscope!!
  20. 21. Chyme finally enters the large intestine… The material that remains after all the absorption has occurred in the small intestine must be eliminated from the body. Large intestine is approx. 1.5 meters long. Chyme is going to be changed into solid waste here.
  21. 22. The water is absorbed back into the bloodstream. Peristalsis slows here and chyme may stay here up to 3 days. Contains bacteria that feed on the material passing through, they make certain vitamins for the body
  22. 23. In the rectum, the waste material is compressed and then eliminated through the anus.
  23. 24. <ul><li>Interesting Facts about Digestion: </li></ul><ul><ul><li>HOW LONG ARE YOUR INTESTINES? At least 25 feet in an adult. Be glad you're not a full-grown horse -- their coiled-up intestines are 89 feet long! </li></ul></ul><ul><ul><li>Chewing food takes from 5-30 seconds </li></ul></ul><ul><ul><li>Swallowing takes about 10 seconds </li></ul></ul><ul><ul><li>Food sloshing in the stomach can last 3-4 hours </li></ul></ul><ul><ul><li>It takes 3 hours for food to move through the intestine </li></ul></ul><ul><ul><li>Food drying up and hanging out in the large intestine can last 18 hours to 2 days! </li></ul></ul>Did you know? Your body makes 2 gallons of digestive juices a day and recycles much of it. That's as much blood as you have in your whole body!

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