1. Anatomy & Physiology II Misericordia University
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. Accessory Organs
Teeth

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 food into a paste consistency)

19. Primary Dentition

20. Adult (Permanent) Dentition

21. Tooth Anatomy
Odontoblasts –secrete dentin Ameloblasts –secrete enamel

22. Pharynx
Function: deglutition Mucosa: Str. Squamous Muscularis: 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: Muscularis: Has three layers
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)

51. Liver Lobule

52. Bile Ducts

53. Bile and Pancreatic Ducts

54. Duodenal Papilla

55. Secretion of Bile

56. Pancreas

57. Pancreas Histology

58. Pancreatic Acinus

59. Exocrine Secretions of Pancreas

60. Secretion of Pancreatic Juice

61. Micelle Formation (Emulsifying Fat)

63. Fatty Acid Absorption

64. Amino Acid Absorption

65. Food Digestion Summary

66. Food digestion Summary