Digestion

1. Digestion

2. Why Do We Need to Digest? Nutrients from food provides us with the energy and materials we need for work, growth and repair The problem is that most of the nutrients we need cannot be used in the form they are eaten Nutrients need to be broken up into their smallest components in order to diffuse into our blood stream

3. What needs to be broken up? • Carbohydrates  simple sugars • Proteins  amino acids • Fats  Glycerol and fatty acids • Enzymes • Type of protein that breaks food molecules into smaller units.

4. The Process of Digestion Divided into 3 stages: • Physical Digestion • Taking food in – Cutting and chewing food • Chemical Digestion • Enzymes break down food even further • Absorption • Wastes are excreted

5. The Assembly Line

6. Mouth Physical digestion starts starch digestion Esophagus Rapid passage of food to stomach

7. Stomach • Digestion of proteins Liver • Digestion of proteins

8. Pancreas Production of many enzymes which digest all types of food Small Intestine Production of more enzymes and absorption of most end products

9. Large Intestine Reabsorption of water Rectum Temporary storage of undigested waste

10. Elimination Removal of undigested wastes

11. Where does digestion begin? On your plate with a fork and knife Your saliva initiates chemical digestion with an enzyme that breaks carbohydrates down into simple sugars Your teeth and tongue break up food into smaller pieces and grind it up

12. Stage 1 Physical Digestion

13. Physical Digestion - Teeth Adult humans have 4 different kinds of teeth (32 total) • Incisors at the very front (4 on top, 4 on bottom) • Canines (cuspids) beside the incisors and are pointed (4 total) • Used for tearing or shredding • Premolars (8 total) • Molars (12 total incl. wisdom teeth) Premolars + molars – flattened on upper surface, used for grinding and chewing tough food

14. Children have deciduous or primary teeth (20 total) 8 Incisors 4 Canines 8 molars

15. Parts of the Teeth Crown - visible part above the gum Root – Part below the gum line, holds tooth in place Enamel – protective coating – hardest substance in the body, cannot be replaced.

16. Parts of the Teeth Dentine – hard bone that gives teeth shape and strength. It is sensitive to temperature, sugar, touch, acids, etc. Pulp Chamber – message center for sensation in the dentine Gum line – help hold and protect teeth

17. Parts of the Teeth Root Canal – carries blood and nerve endings Cementum – connect tooth to the jaw bone

19. Carnivores – Sharp teeth for grabbing food and ripping it apart Herbivores – Flat teeth for grinding food Omnivores – Flat and sharp teeth

20. What causes tooth decay? • Bacteria called plaque live in your mouth • Plaque eats any food that stays on your teeth • Produce acid that eats away the enamel, creating pits called cavities • Build up of a hard crust called tartar NOTE: Sugar does not cause tooth decay, it feeds the bacteria that do

21. How to maintain healthy teeth Brushing and flossing removes plaque and keeps gums healthy Wear mouth guards in sports Regular dental checkups (clean away tartar) Diet: calcium, phosphorus, vitamins A, C & D all help maintain teeth and gums

22. Some Dental Problems • Sensitivity due to the removal of enamel by cavities and exposing dentine • Abscesses – bacteria get into the root and infect it • Peridontal Disease – Affect the tissue around the teeth. Includes retreating gum line, sore gums or bleeding. Usually caused by poor diet or hygiene. • Halitosis – bad breath caused by smoking, infections, tooth decay, sinus infections, etc.

24. Stage 2 Chemical Digestion

25. Begins In the Mouth Amylase • 1st enzyme to act. • Produced by saliva • Helps break down starch into sugar molecules.

26. Saliva • Produced by 3 pairs of glands inside the mouth • Is slightly acidic • Approx 1000 mL produced per day! • 99% is water

27. Function of Saliva • Moistens dry food • Binds the loose crumbs together so bits do not get into the respiratory system • Softens food so rough edges will not scratch the walls • Enzyme amylase begins chemical digestion

28. Structures in the Mouth Hard Palate Soft Palate Uvula

29. The Tongue • Attached to the floor of the mouth • Helps to move food to the molars • Mixes food with saliva

30. The Tongue Once the food is moist and soft, the tongue rolls it into a ball called a bolus. This prepares the food to pass into the pharynx to be swallowed.

32. Swallowing The tongue moves the bolus of swallowed food to the back of the mouth The soft palate moves upward to partially seal off the nasal passage At the same time, the epiglottis closes the opening into the respiratory passage

34. Amylase in Action • Place cracker in mouth • Chew WITHOUT SWALLOWING! • Note the taste • Leave on tongue until you notice a taste change (can take up to 5 min) • What do you taste?

35. The Sense of Taste Humans detect taste with taste receptor cells These are clustered into taste buds Taste buds are clustered into bumps called papillae There are 5 primary taste sensations • salty • sour • sweet • bitter • Umami (Savory)

37. Muscular Contractions The movement of food from the tongue down into the pharynx is under voluntary control The second stage, involving the epiglottis and the movement of the food into the esophagus, is involuntary

38. The Esophagus • Flexible tube – approx. 25 cm long • Leads from the pharynx to the stomach • Walls have 2 layers of muscle • The inner lining covered with mucus – helps food pass through easily

39. Peristalsis Bolus is moved through peristaltic action Peristalsis - the rhythmic contractions of muscles – like squeezing a tube of tooth paste

40. Cardiacsphincter: • Ring of muscle that controls thepassage of bolus into stomach – like pulling a drawstring

41. The Stomach • Large muscular bag that stretches as it fills with food • Can hold 1.5 L • Made up of many layers, including 3 layers of muscle

42. Gastric glands produce gastric juice. • Pepsin (an enzyme) – Breaks down protein • Hydrochloric Acid • The muscular walls of the stomach contract to mix food with gastric juice, producing a mixture called chyme.

43. Hydrochloric Acid (HCL) • Lowers the pH of the stomach to allow enzymes to work efficiently • Helps kill bacteria • Mucus secretions protect the stomach walls from HCl • BUT sometime mucus is not enough and HCL and digestive enzymes eat away at the lining, resulting in a peptic ulcer.

44. Heart Burn Presence of stomach acid in the esophagus Cardiac sphincter is not working properly – opens allowing acidic stomach contents into the esophagus

45. http://videos.howstuffworks.com/hsw/17648-food-into-fuel-the-process-of-digestion-video.htmhttp://videos.howstuffworks.com/hsw/17648-food-into-fuel-the-process-of-digestion-video.htm

46. The pyloric sphincter is located at the lower end of the stomach • Controls the flow of partially digested food (Chyme) out of the stomach

47. The Small Intestine • 2.5 cm in diameter, and is about 7m in length Esophagus Small Intestine Stomach

48. Small Intestine • A long coiled and looped tube • Fills most of the abdomen • Held in place by a membrane called mesentery

49. 4 functions of the Small Intestine • Keeps the food moving by peristalsis • Secretes enzymes which continue the digestive process • The site where digestion by chemicals from the pancreas and liver take place • Nutrients are absorbed into the bloodstream

50. Digestive processes… 3 basic food substances in the small intestine: • Carbohydrates • Fats • Proteins They are broken down into molecules that are small enough to pass through the wall and enter the circulatory system