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 Esophagus Physical digestion starts starch digestion
Rapid passage of food to stomach

7. Stomach
Digestion of proteins
Liver
Digestion of proteins

8. Pancreas Small Intestine
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 Rectum Reabsorption of water
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. Cardiac sphincter:
Ring of muscle that controls the passage 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

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

51. The Pancreas
Produce pancreatic juice – which contain about 28 enzymes and sodium bicarbonate
Lipase – breaks down fat
Amylase – completes carbohydrate digestion
Trypsin and peptidase – complete protein digestion
Sodium bicarbonate neutralizes the acidic chyme as it comes out of the stomach

52. How are our bodies built to handle the acid in our stomach?
Great Test Question!
How are our bodies built to handle the acid in our stomach?

54. The Liver Produces bile that is stored in the gall bladder
Bile emulsifies fat – which means that it helps fat dissolve in water so it can be digested and absorbed

56. So How Do We Get Nutrients From Food?
Absorption Stage 3

57. Absorption of Nutrients
Surface of the small intestine is folded
Covering the surface are projections called villi
Villi:
Increase surface area for absorption
Collect the nutrients and transport them to where they are needed in the body

58. What Happens Next?
Reabsorption and Elimination: The Large Intestine

59. The Large Intestine consists of:
Cecum
Appendix
Colon
Rectum

60. The Large Intestine Approx. 1.5 m in length 7.6 cm in diameter
Functions mainly to reabsorb water

61. Cecum – Where the small intestine empties into the large intestine
Appendix
Believed to have no function
Can become infected –called appendicitis

62. Large Intestine function
Reabsorbs water and maintains the fluid balance of the body
Absorbs certain vitamins
Undigested food is dried into suitable consistency for defecation
Stores waste before it is eliminated

63. The Rectum Last section of the digestive tract
Ends with the anal sphincter (like a drawstring)
When full there is a mild feeling of discomfort, which tells us that the feces is ready to be eliminated

64. What Your Feces Can tell you…
Feces are 75% water and 25% solids
Diet lacking fiber = drier, compacted feces which can result in constipation
Sufficient fiber = Holds more water and is much softer which allows it to pass through easily

65. Quick Recap… Small Intestine: Breaks down food and absorbs nutrients
Villi increase’s surface area = more absorption
Moves the rest to the large intestine (through peristalsis)

66. Quick Recap Large Intestine: Removes water
Moves undigested food (peristalsis) to be released as waste

67. http://videos. howstuffworks