1. MD13.00 Digestive System MD 13.01 Structure of Digestive System
MD Function of Digestive System

2. The Digestive System
DIGESTION – the process of changing complex solid foods into simpler soluble forms which can be absorbed by body cells.
ENZYMES – chemical substances that promote chemical reactions in living things.
Digestion is performed by the digestive system which includes the alimentary canal and accessory organs.

3. The Digestive System
ALIMENTARY CANAL – digestive tract or gastrointestinal tract (GI Tract). A 30 ft. tube from mouth to anus. Includes pharynx, esophagus, stomach, small and large intestine.

4. The Digestive System
Walls of alimentary canal is composed of 4 layers:
Mucosa innermost layer Secretes mucous which lubricates canal and protects canal from powerful enzymes.
Submucosa connective tissue, blood vessels, and nerve endings.
Circular muscles
Longitudinal muscles

5. Accessory Organs Of Digestion
Tongue
Teeth
Salivary glands
Pancreas
Liver
Gall bladder

6. Lining of the Digestive System
PERITONEUM – double-layered serous membrane that lines the abdominal cavity

7. Functions of the Digestive System
Physical breakdown of food
Chemical digestion of food into the end products of fat, carbohydrates and protein.
Absorb nutrients into blood capillaries of the small intestines
Eliminate waste products of digestion

8. MOUTH Food enters digestive system through mouth (BUCCAL CAVITY)
Inside of mouth covered with mucous membrane
Roof of mouth is HARD PALATE (bone) and soft palate
UVULA – flap that hangs off soft palate – prevents food from going up the nose when you swallow

9. UVULA

10. TONGUE Attached to four bones (hyoid, mandible, 2 temporals)
Helps in chewing and swallowing
Made of skeletal muscle, controlled by Hypoglossal nerve (XII)
Papillae (taste buds) on the surface

11. Taste Bud Locations

12. SALIVARY GLANDS Three pairs of glands Secrete saliva
Parotid – largest salivary glands, they become inflamed during mumps located in front of and below ear.
Submandibular located at angle of lower jaw.
Sublingual under sides of tongue
Secrete saliva

13. SALIVARY GLANDS

14. TEETH GINGIVA – gums, support and protect teeth
MASTICATION – chewing, teeth help in mechanical digestion
DECIDUOUS teeth – baby teeth (#20)
Adult mouth has 32 teeth

15. TEETH Inside tooth: Pulp cavity filled with nerves and blood supply
Pulp cavity surrounded by calcified tissue (dentin)
On crown portion, dentin covered by enamel.

16. Inside a tooth

17. ESOPHAGUS Muscular tube, 10” long Connects pharynx and stomach
4 layers – mucosa, submucosa, muscular and external serous layer
Muscles in upper 1/3 are voluntary, lower 2/3 is smooth muscle and involuntary

18. STOMACH Upper part of abdominal cavity
Fundus
Upper part of abdominal cavity
CARDIAC SPHINCTER – circular layer of muscle, controls passage of food into stomach
PYLORIC SPHINCTER – valve, regulates the entrance of food into duodenum
Greater Curvature
Pylorus

19. STOMACH
RUGAE – mucous coat lining of stomach in folds when the stomach is empty
Stomach has muscular coat that allows it to contract (peristalsis) and push food into the small intestine

20. SMALL INTESTINE
Same four layers as stomach and esophagus – mucosa, submucosa, muscle layer, serosa
DUODENUM – first segment, curves around pancreas, 12” long
JEJUNUM – next section, 8 ft. long
ILEUM – final portion, feet long

21. SMALL INTESTINE

22. ABSORPTION
In small intestine, digested food passes into bloodstream and on to body cells, indigestible passes on to large intestine
Contains millions of villi, each consisting of a network of blood and lymph capillaries. Digested food passes through villi into bloodstream
Indigestible portion goes to large intestine.

23. Small Intestine with Villi

24. Accessory Organs of Digestion

25. PANCREAS Located behind stomach
Exocrine function – secretes digestive enzymes; maltase, lactase, sucrase and lipase
Also has endocrine function
Exocrine- secretes through a duct.
Endocrine-secretes directly into bloodstream

26. LIVER Largest organ in the body
Located below the diaphragm, upper right quadrant
Manufactures bile (digests fats)
Connected to gallbladder and small intestine by ducts
Gall Bladder

27. LIVER Functions Produce and store glucose in the form of GLYCOGEN
Detoxify alcohol, drugs and other harmful substances
Manufacture blood proteins (fibrinogen, prothrombin for clotting, albumin for fluid balance and globulin for immunity)
Prepare urea from the breakdown of amino acids
Store Vitamins A, D and B complex

28. GALL BLADDER Small green organ, inferior surface of the liver
Stores and concentrates bile until needed by the body
When fatty foods digested, bile released by gallbladder

29. GALL BLADDER

30. LARGE INTESTINE
Ileum empties CHYME (semi-liquid food) into large intestine through ileo-cecal valve.
Approx 2” in diameter, 5 feet in length
Also called the colon

31. LARGE INTESTINE CECUM – lower right portion of large intestine
APPENDIX is finger-like projection off cecum. Blind sac that fills quickly and empties slowly. Irritation of lining can lead to bacterial growth-Appendicitis.
RECTUM – last portion of large intestine
ANUS – external opening

32. LARGE INTESTINE

33. Digestion

34. Digestion Terms
BOLUS – soft, pliable ball – creating from chewing and addition of saliva – it slides down esophagus
PERISTALSIS – wavelike motions, moves food along esophagus, stomach and intestines

35. In the mouth… Saliva softens food to make it easier to swallow
PTYALIN (salivary amylase) in saliva converts starches into simple sugar
Salivary glands are under nervous control – just thinking of food can cause your mouth to water
Food mechanically broken down by teeth.
Food passes through esophagus by peristalsis.

36. In the stomach… Cardiac sphincter relaxes and food enters.
Gastric (digestive) juices are released
Stomach walls churn and mix (This mixture is chyme)
Small amount of chyme enters duodenum at a time - controlled by pyloric sphincter
Takes 2-4 hours for stomach to empty
Only substances absorbed by stomach are alcohol and some medicines.

37. In the small intestine…
Digestion is completed and absorption occurs
Addition of enzymes from pancreas and bile from liver/gallbladder
Peristalsis and segmental movement moves food back and forth until completely broken down.

38. In the small intestine…
Absorption occurs when:
carbohydrates are converted to glucose
proteins broken down to amino acids
fats changed to fatty acids and glycerol
Nutrients transferred to blood by villi.
Undigested food enters large intestine by ileo-cecal valve.

39. In the small intestine…
Muscle Layer
Submucosa
Mucous membrane
Serosa

40. In the large intestine…
Regulation of H2O balance by absorbing large quantities back into bloodstream
Also absorbs Vitamin B complex and K
Bacterial action on undigested food – decomposed products excreted through colon – Bacteria form moderate amounts of B complex and Vitamin K

41. In the large intestine…
Gas formation – 1-3 pints/day, pass it through rectum (flatulence) 14 times a day, bacteria produce the gas
Feces – undigested semi-solid consisting of bacteria, waste products, mucous and cellulose
Defecation – when large intestine fills, defecation reflex triggered – colon and rectal muscles contract while internal sphincter relaxes – external anal sphincter under conscious control

42. Digestive Disorders

43. GERD Gastroesophageal Reflux Disease
Cardiac sphincter is weak and relaxes inappropriately
Stomach contents flow up into esophagus
Symptom – heartburn

44. GERD

45. HIATAL HERNIA
When stomach protrudes above diaphragm through esophageal opening
More common in people over 50
One of symptoms is also heartburn. Change in diet may relieve.
Surgery only occasionally necessary.

46. HIATAL HERNIA

47. HEARTBURN
Acid reflux
Backflow of highly acidic gastric juices into lower end of esophagus. Irritates lining which causes burning.
Symptom – burning sensation
Rx – avoid chocolate and peppermint, coffee, citrus, fried or fatty foods, tomato products – stop smoking – take antacids – don’t lay down 2-3 hours after eating

48. PYLORIC STENOSIS
Narrowing of pyloric sphincter, often found in infants
Symptom – projectile vomiting
Rx – surgery

49. PYLORIC STENOSIS

50. GASTRITIS Acute or chronic inflammation of the stomach lining.
Many different causes.

51. GASTROENTERITIS
Inflammation of mucous membrane lining of stomach and intestine
Common cause - virus
Symptoms – diarrhea and vomiting for hours
Complication = dehydration
Treat the symptoms.

52. ULCER Sore or lesion that forms in the mucosal lining of the stomach
Gastric ulcers in the stomach and duodenal ulcers in the duodenum
Cause – H. pylori (bacteria) is primary cause

53. ULCER
Lifestyle factors that contribute: cigarette smoking, alcohol, stress, certain drugs
Symptoms – burning pain in abdomen, between meals and early morning, may be relieved by eating or taking antacid
Diagnosis – x-ray, presence of bacteria
Rx – H2 blockers (drugs) that block release of histamine

54. ULCER

55. COLITIS (IRRITABLE BOWEL SYNDROME)
Also called Crohn’s disease.
Large intestine inflamed
Cause – unknown
Symptoms – episodes of constipation or diarrhea

56. COLITIS (IRRITABLE BOWEL SYNDROME)

57. APPENDICITIS When appendix becomes inflamed
If it ruptures, bacteria from appendix can spread to peritoneal cavity causing PERITONITIS

58. APPENDICITIS

59. HEPATITIS A Infectious hepatitis Cause – virus
Spread through contaminated food or H2O

60. HEPATITIS B (Serum Hepatitis)
Caused by virus found in blood
Transmitted by blood transfusion or being stuck with contaminated needles (drug addicts)
Health care workers at risk and should be vaccinated
Use standard precautions for prevention

61. CIRRHOSIS Chronic, progressive disease of liver
Normal tissue replaced by fibrous connective tissue
75% caused by excessive alcohol consumption

62. CIRRHOSIS

63. CHOLECYSTITIS
Inflammation of gallbladder

64. CHOLELITHIASIS
Gallstones made of crystallized cholesterol that combines with bile salts and bile pigments.
Can block the bile duct causing pain and digestive disorders
Small ones may pass on their own, large ones surgically removed
Surgical removal of gallbladder = CHOLECYSTECTOMY

65. CHOLELITHIASIS

66. LAPAROSCOPIC CHOLECYSTECTOMY
Most common method of cholecystectomy
Small abdominal incisions allow insertion of surgical instruments and small video camera
Surgeon performs procedure by watching monitor and manipulating instruments
Stomach muscles are not cut, healing is quicker

67. LAPAROSCOPIC CHOLECYSTECTOMY

68. PANCREATITIS Inflammation of pancreas 1/3 of cases = cause unknown
Sometimes associated with chronic alcoholism 

69. DIVERTICULOSIS Little sacs (diverticuli) develop in wall of colon
Most people over age 60 have this
When the sacs become inflamed = DIVERTICULITIS

70. DIVERTICULOSIS

71. DIARRHEA
Loose, watery, frequent bowel movements when feces pass along colon too rapidly
Caused by infection, poor diet, nervousness, toxic substances or irritants in food

72. CONSTIPATION When defecation delayed, feces become dry and hard
Rx – diet with cereals, fruits, vegetables, (roughage), drinking plenty of fluids, exercise, and avoiding tension

73. COLON CANCER Early detection critical – COLONOSCOPY after age 50
HEMOCCULT – stool slide specimen to look for hidden blood
Rx – colon resection
COLOSTOMY – opening in abdomen, healthy bowel brought to skin after cancer removed, pouch worn to collect waste 

74. COLON CANCER

75. COLOSTOMY

76. CARIES
Tooth decay (cavities)

77. CARIES

78. GINGIVITIS
Inflammation of the gums

79. JAUNDICE
Yellow color when bile pigment gets in bloodstream

80. JAUNDICE