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Introduction to digestion

Introduction to digestion. OM NOM NOM. Why do we eat?. To gain various nutrients needed for our life processes. Cellular respiration Tissue growth and repair Keep us strong and healthy . Nutrients in food. Proteins. Fats. Carbo -hydrates. Vitamins. Minerals. Complex Carbo -hydrates.

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Introduction to digestion

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  1. Introduction to digestion OM NOM NOM

  2. Why do we eat? • To gain various nutrients needed for our life processes. • Cellular respiration • Tissue growth and repair • Keep us strong and healthy

  3. Nutrients in food Proteins Fats Carbo-hydrates Vitamins Minerals ComplexCarbo-hydrates Single sugars Doublesugars

  4. Why digestion? • Complex molecules such as starch, proteins and fats are too large • cannot be absorbed by the bloodstream • cannot diffuse through partially permeable cell membranes Purpose of digestion: Break down large food molecules into smaller ones so that they can be absorbed and used by our body cells Walls of the small intestine Bloodstream

  5. Physical digestion • Digestion • Chemical digestion

  6. An enzyme is a special type of protein that speeds up chemical reactions in the body, but remains unchanged at the end of the reaction • Enzymes are specialised– they can only work on specific substrates Substrate does not fit this enzyme

  7. Let us look at the types of digestive enzymes required to break down complex food molecules into smaller molecules. Carbohydrase • Proteins • Fats • Starch • Maltose • Fatty acids • Amino acids • Glucose Amylase Maltase Protease • Glycerol Lipase

  8. The digestive system OM NOM NOM

  9. Alimentary canal? What’s that?

  10. The Alimentary Canal The alimentary canal is a continuous tube in the body starting from the mouth and ending at the anus.

  11. What is the alimentary canal made up of? • Mouth • Oesophagus • Stomach • Small intestine • Large intestine • Rectum • Anus

  12. What is the digestive system made up of? • Mouth • Salivary glands • Oesophagus • Stomach • Liver • Small intestine • Gall bladder • Large intestine • Pancreas • Rectum • Anus

  13. Gotta label ’em all mouth salivary gland • oesophagus liver stomach gall bladder • pancreas • small intestine • large intestine rectum anus

  14. Hold on tight… It’s time for journey down the alimentary canal! Yipee! Here we go!

  15. 1st stop: The Mouth What type of digestion occurs when Cookie Monster is munching his cookies? Physical / Mechanical Digestion

  16. 1st stop: The Mouth Purpose of physical digestion? The teeth help to break largefood pieces into smallerpieces, resulting in an increase in surface areaexposed to digestive enzymes.

  17. 1st stop: The Mouth What happens concurrently with physical digestion? Chemical Digestion

  18. 1st stop: The Mouth Chemical digestion: Amylase • Starch • Maltose Food is mixed with saliva produced by salivary glands. Saliva contains amylase, which breaks down starch into maltose.

  19. 1st stop: The Mouth The tongue helps to mix the food with the saliva and rolls the partially digested food into a small ball (bolus) which is then swallowed into the oesophagus.

  20. 1st stop: The Mouth What’s next? Down the oesophagus!

  21. Down the Oesophagus…

  22. 2nd stop: Oesophagus Also known as gullet. A long and narrow tube joining the mouth and the stomach. No enzymes = No digestion

  23. 2nd stop: Oesophagus Has strong muscles in its walls. These muscles contract and relax to produce a wave-like movement that pushes the food into the stomach.

  24. 2nd stop: Oesophagus These muscles contract and relax to produce a wave-like movement that pushes the food into the stomach. This involuntary wave-like pattern of contractions is called peristalsis.

  25. Digest me my beloved gastric juice…

  26. 3rd stop: Stomach • The stomach is a large muscular bag. • It canexpand to take in various amounts of food. • It can contract to churn the food to mix it with gastric juice, a type of digestive juice produced by the stomach lining.

  27. 3rd stop: Stomach Physical Digestion: Peristalsis in the stomach wall churns and breaks up the food. Peristalsis also mixes the food well with gastric juice

  28. 3rd stop: Stomach Gastric juice contains Hydrochloric acid (HCl) Proteases

  29. 3rd stop: Stomach Functions of HCl: Provides acidiccondition in the stomach for the proteases to work. Kills bacteria which may have been swallowed with the food.

  30. 3rd stop: Stomach Protein Chemical Digestion: The proteases in the stomach digest the proteins in the food into shorter chains of amino acids. Proteases Amino acids

  31. Thinking time… Why does the stomach not “digest” itself?

  32. Hint: Structure of stomach wall

  33. Thinking time… Cells lining the stomach produce a thick layer of mucus which coats the inner wall of the stomach. The mucus protects the stomach from digesting itself and from the corrosive action of the hydrochloric acid.

  34. 3rd stop: Stomach The food stays in the stomach for a few hours and is slowly moved by peristalsis to the small intestine. By the time the food leaves the stomach, it would have turned into a thick semi-liquid called chyme.

  35. Now… to small intestine

  36. 4th stop: Small Intestine Small intestine: A long and narrow tube joining the stomach and the large intestine.

  37. 4th stop: Small Intestine As the chyme enters the small intestine from the stomach, it is mixed with secretions from Liver Pancreas Small intestine

  38. 4th stop: Small Intestine The small intestine is where most of the chemical digestion and absorption of food takes place. Note: liver, gall bladder and pancreas are not part of the alimentary canal, but they are parts of the digestive system.

  39. 4th stop: Small Intestine Liver: Produces a liquid called bile Bile is stored in gall bladder and released into the small intestine through the bile duct. Gall bladder

  40. 4th stop: Small Intestine • Function of bile: • Emulsifies fats by breaking it into small droplets • Increases total surface area of fat droplets to speed up digestion by lipase

  41. Gallstones • Develop when bile contains too much cholesterol and not enough bile salts • Due to diet, weight, medication • Removed surgically or through the use of medication to dissolve them slowly

  42. 4th stop: Small Intestine • Pancreas • Produces pancreatic juices • Pancreatic juice • Contains amylase, proteases, lipase pancreas

  43. 4th stop: Small Intestine • Small intestine • Produces intestinal juices • Intestinal juice • Contains maltase, proteases, lipase

  44. 4th stop: Small Intestine Main end products of digestion: • Glucose • Amino acids • Glycerol • Fatty acids

  45. These products are now small enough to pass through the wall of the small intestine and into the bloodstream. Walls of the small intestine Bloodstream

  46. Wall of small intestine

  47. Last stop: Large Intestine The undigested food moves from the small intestine into the large intestine by peristalsis.

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