1. Digestive System

2. Functions
Digestion – breakdown
Absorption

3. Organization Alimentary Canal - Gastrointestinal (GI) Tract
Mouth to anus
30 feet long

4. Organization (cont’d)
Accessory Organs
Found either within the alimentary canal or outside it and communicate with it by way of ducts
Teeth, salivary glands, tongue, pancreas, liver, and gallbladder

5. Mucous Membranes System lined with mucous membrane
Kept moist for lubrication and absorption

6. Tunics
Walls of alimentary canal from esophagus to large intestine lined with 4 basic layers (tunics)

7. Tunics (cont’d) Mucosa Innermost layer lines lumen of organ Submucosa
Nerves, blood vessels, glands

8. Tunics (cont’d) Muscularis externa Smooth muscle Inner circular layer
Outer longitudinal layer
Combined contraction causes peristalsis

9. Tunics (cont’d) Serosa Outermost Visceral peritoneum
Continuous w/ parietal peritoneum
Mesentery
Greater and lesser omentum

11. Digestive Processes
Ingestion
Propulsion
Peristalsis
Segmentation

12. Digestive Processes (cont’d)
Mechanical digestion
Chewing, churning, etc.
Prepares food for further breakdown by enzymes

13. Digestive Processes (cont’d)
Chemical digestion
Large food molecules broken down to building blocks by enzymes
Carbohydrates  monosaccharides
Proteins  amino acids
Lipids  fatty acids and glycerol
Absorption
Elimination - Defecation

15. Digestive Organs

16. Mouth Lips and cheeks Palate – roof Tongue – floor
Forms bolus (ball) of food
Attached to hyoid bone and styloid process of skull
Frenulum

17. Mouth (cont’d) Teeth Digestive processes of mouth
Deciduous (baby) teeth
Permanent teeth
Digestive processes of mouth
Food ingestion
Mechanical – mastication (chewing)
Chemical - starches

18. Salivary Glands Parotid glands Near ears Mumps Submandibular gland
Inside jaw
Sublingual gland
Under tongue
Digestive processes
Chemical breakdown of starches

19. Pharynx/Esophagus Pharynx Esophagus Digestive processes Gullet
Conducts food to the stomach
Digestive processes
Food propulsion
Swallowing – deglutition
Peristalsis

20. Stomach
Cardioesophageal sphincter
Cardiac region
Fundus

21. Stomach (cont’d)
Body
Pylorus
Pyloric sphincter or valve

22. Stomach (cont’d) When full, can hold about 4L of food
When empty, collapses inward on itself
Large folds – rugae

23. Stomach (cont’d) Walls have 3rd muscle layer – oblique
Allows churning and mixing of food

24. Stomach (cont’d) Gastric glands produce:
HCl, pepsin, rennin, mucus (protects stomach from digesting itself), gastrin, and intrinsic factor
Chyme – semifluid; passes on to the sm. intestine

25. Stomach (cont’d) Digestive processes Mechanical – churning
Chemical – proteins
Propulsion - peristalsis

26. Small Intestine Major digestive organ 6m long Three subdivisions:
Duodenum
Jejunum
Ileum

27. Small Intestine (cont’d)
Microvilli, villi, and circular folds
Increase surface area for enhanced absorption

28. Small Intestine (cont’d)
Pancreatic juice and bile enter duodenum

29. Small Intestine (cont’d)
Digestive processes
Food digestion (chemical) of carbohydrates, proteins and lipids completed here
Absorption of water and end products of digestion also completed here
Mechanical – bile – emulsifies
Propulsion - peristalsis

30. Large Intestine
Subdivisions
Cecum
Appendix
Colon
Rectum
Anal Canal

31. Large Intestine (cont’d)
Digestive processes
Food breakdown
Bacteria metabolize remaining nutrients to produce vitamins (K & some B)
Reabsorbs these vitamins, bile salts, and water
Propulsion
Peristalsis and mass movements
Elimination – defecation - remainder of undigested food– feces

32. Pancreas Pancreatic juice
Contains enzymes that break down all categories of food
Secreted into the duodenum in an alkaline fluid (neutralizes acidic chyme)

33. Liver Largest gland of body Produces bile Emulsifies fat
Enters duodenum through bile duct

34. Gallbladder
When food digestion is not occurring, bile backs up into gallbladder to be stored

36. Homeostatic Imbalances

37. Homeostatic Imbalances
Appendicitis
Inflammation of appendix
If ruptures, spread infection throughout peritoneal cavity – peritonitis – life-threatening
Gallstones
If bile stored too long in gallbladder or too much water is removed – cholesterol crystallizes
Heartburn
Cardioesophageal sphincter fails to close tightly – gastric juices backs up into esophagus

38. Homeostatic Imbalances (cont’d)
Hiatal Hernia
Superior part of stomach protrudes slightly above diaphragm
Gastric juice flows into unprotected esophagus
Ulcers
Erosion of mucosa of any part of GI tract exposed to secretions of stomach
Duodenal ulcer 3x more common than gastric ulcer
Bacteria Helicobactor pylori now believed to be major cause of ulcers

39. Homeostatic Imbalances (cont’d)
Emesis
Vomiting
Like a reverse peristalsis
Caused by irritation of stomach or disturbance of equilibrium
Diverticulitis
Diverticula (mucosa protrusions thru colon walls) become inflamed.
May be caused by chronic constipation and low-fiber diet

40. Homeostatic Imbalances (cont’d)
Diarrhea
Food rushed thru large intestines before water can be absorbed
Constipation
Food remains in large intestine for extended time – too much water is absorbed
Hepatitis
Inflammation and death of liver tissue
Usually caused by viruses
May be caused by chemical toxins

41. Homeostatic Imbalances (cont’d)
Colitis
Inflammation of colon and rectum
May be chronic (usually inherited) or acute (caused by irritation of bowel due to diet or infection)

42. Homeostatic Imbalances (cont’d)
Cancer
Stomach and pancreatic
Highly metastatic
Usually fatal
Colon
Common
Fatal if not treated early