Digestion

1. Digestion Anatomy & Physiology II Tony Serino, Ph.D. Biology Department Misericordia University

2. Digestion • The reduction through mechanical and chemical means (hydrolysis) of complex food substances into simple monomers and their absorption into the internal environment.

3. Functions of Digestive System • Motility(Propulsion) • Ingestion –food enters tract • Mastication -chewing • Deglutition -swallowing • Transportation through tract (peristalsis) • Mixing • Egestion (Defecation) • Secretion • Endocrine and Exocrine secretions • Digestion • mechanical and chemical breakdown of food • Absorption • Passage of food particles from external to the internal environment

4. Major Organs of System

5. Teeth Accessory Organs

6. GI Tract Development Post-gastrula Late Gastrulation Pylorus

7. Basic Histology of Digestive Tract (Auerbach’s) (Meissner’s) (LOCI)

8. Tube Movements Peristalsis Segmentation

9. Retroperitoneal Position

10. Peritoneal Cavity Lesser Peritoneal Cavity Greater Peritoneal Cavity

11. Mesenteries

12. Mesenteries

13. Control of Overall GI Tract Activity

14. Oral Cavity (sagittal) • Mucosa: Stratified Squamous epithelia • Muscularis: Skeletal muscle overlying bone • Functions: • Ingestion • Mastication • Hydration of food • Begins chemical digestion • Formation of bolus

15. Oral Cavity (anterior) (Red Margin)

16. Tongue Functions: mixing, speaking, and swallowing Intrinsic and extrinsic muscles Foliate papillae Three layers of skeletal muscle.

17. Major Salivary Glands Secrete saliva –mixture of water, mucus, electrolytes, antibodies and enzymes. Enzyme is salivary amylase which breaks down starches.

18. Teeth Function: mastication (chewing and grinding of foodinto a paste consistency)

19. Primary Dentition

20. Adult (Permanent) Dentition

21. Tooth Anatomy Odontoblasts –secrete dentinAmeloblasts –secrete enamel

22. Pharynx Function: deglutitionMucosa: Str. SquamousMuscularis: Skeletal

23. Esophagus • Function: Deglutition • Two sphincters: upper and lower esophageal sphincters (lower is physiological only) • Retropleural position (therefore, covered by adventitia) • Mucosa: stratified squamous with many mucus glands (esophageal glands) • Muscularis: changes from skeletal to smooth muscle

24. Esophagus Histology

25. Deglutition (Swallowing)

26. Deglutition (cont’d)

27. Stomach (cadaver) • J-shaped muscular pouch • Receives bolus and produces chyme • Liquefies food by mixing it with HCl and vigorous churning • Low pH stops amylase activity, but secretes pepsinogen (pepsin) that begins break down of proteins • Absorbs little except imbibed water, electrolytes, and some drugs (ie. alcohol and aspirin)

28. Stomach Anatomy • Mucosa: • simple columnar folded into rugae • No villi • Openings leading to gastric pits and glands • Muscularis: • Has three layers

29. Rugae of Stomach Temporary longitudinal foldings of the mucosa

30. Stomach Histology

31. Gastric Gland

32. Regulation of Gastric Juice

33. Gastric Emptying

34. Gastric Emptying

35. Inhibition of Gastric Emptying

36. Small Intestine

37. Small Intestine

38. Duodenum and Accessory Organs

39. Small Intestine Structures to Increase Surface Area Plica Circularis Villi Long Length of SI

40. Small Intestine Histology

41. Histology Changes in Intestine

42. Villi Histology

43. Large Intestine (x-ray)

44. Large Intestine (Colon)

45. Large Intestine Histology

46. Anal Canal

47. Defecation Reflex

48. Upper Abdominal XS

49. Liver

50. Liver (inferior surface)