1. DIGESTIVE SYSTEM 3 major components: 3 major components: 1.Oral cavity. 2.Alimentary canal. 3.Associated Glands: Salivary glands.Salivary glands. Liver.Liver. Pancreas.Pancreas.

2. Wall of the Alimentary Canal Four concentric layers: 1.Mucosa: –Epithelial Lining: Simple columnar epithelium (in stomach & intestine).Simple columnar epithelium (in stomach & intestine). –Lamina propria: Connective tissue.Connective tissue. It contains mucosal glands.It contains mucosal glands. –Muscularis mucosae: 2 layers of smooth muscle cells.2 layers of smooth muscle cells. Serosa

3. Wall of the Alimentary Canal 2.Submucosa: Connective tissue containing blood vessels & nerves. May contain glands (as in duodenum). 3.Muscularis Externa: 2 smooth muscle layers: Inner circular layer.Inner circular layer. Outer longitudinal layer.Outer longitudinal layer. 4.Serosa: Connective tissue covered by mesothelium (simple squamous epithelium). Serosa

4. STOMACH It has 4 regions: cardia, fundus, body and pylorus. It has 4 regions: cardia, fundus, body and pylorus. fundus body pylorus cardia

5. Fundus of Stomach Mucosa: Mucosa: Shows gastric pits in which open the fundic glands. –Epithelial lining: simple columnar epithelium (mucus-secreting). NO goblet cells. –Lamina propria: Connective tissue containing numerous fundic glands. –Muscularis mucosae: 2 layers of smooth muscle.

6. Fundus of Stomach Submucosa: Submucosa: –Connective tissue containing blood vessels & nerves. –NO glands. Muscularis Externa: Muscularis Externa: –3 smooth muscle layers: Inner oblique.Inner oblique. Middle circular.Middle circular. Outer longitudinal.Outer longitudinal. Serosa: Serosa: –Connective tissue covered by mesothelium.

7. Fundic Glands Simple branched tubular glands. Simple branched tubular glands. Have short narrow ducts (pits). Have short narrow ducts (pits). Numerous; occupying most of the lamina propria. Numerous; occupying most of the lamina propria. Perpendicular to the surface. Perpendicular to the surface.

8. Fundic Glands Composed of 5 cell types: 1.Parietal cells: secrete HCl and gastric intrinsic factor that helps absorption of vitamin B 12. 2.Peptic (chief) cells: secrete pepsin. 3.Mucous neck cells: secrete mucus. 4.Enteroendocrine cells: secrete hormones. 5.Stem cells: regenerative cells.

9. SMALL INTESTINE It has 3 regions: duodenum, jejunum and ileum. It has 3 regions: duodenum, jejunum and ileum. To increase surface area the mucosa has: To increase surface area the mucosa has: –Villi. –Crypts (intestinal glands).

10. Duodenum 1.Mucosa: Shows villi and crypts. –Epithelium: simple columnar epithelium with goblet cells. –Lamina propria: Connective tissue containing intestinal glands (crypts). –Muscularis mucosae: 2 layers of smooth muscle cells.

11. Duodenum 2.Submucosa: –Connective tissue containing blood vessels and nerves. –Contains Brunner’s glands (secrete mucus). 3.Muscularis Externa: –2 smooth muscle layers: Inner circular layer.Inner circular layer. Outer longitudinal layer.Outer longitudinal layer. 4.Serosa: –Connective tissue covered by mesothelium.

12. Intestinal Glands (Crypts) Simple tubular glands that open between villi. Simple tubular glands that open between villi. Composed of 5 cell types: Composed of 5 cell types: 1.Columnar cells: absorptive. 2.Goblet cells: secrete mucus. 3.Paneth cells: secrete lysozyme (antibacterial). 4.Enteroendocrine cells: secrete hormones. 5.Stem cells: regenerative cells.

13. LARGE INTESTINE It is composed of: It is composed of: –Appendix, –Cecum, –Colon (ascending, transverse, descending & sigmoid), –Rectum, and –Anal canal.

14. Colon 1.Mucosa: Shows only crypts (NO villi) –Epithelium: simple columnar epithelium with numerous goblet cells. –Lamina propria: Connective tissue containing numerous crypts. Cells of the crypts are the same as in small intestine but NO Paneth cells. Lymphatic nodules: frequent. –Muscularis mucosae: 2 layers of smooth muscle.

15. Colon 2.Submucosa: –NO glands. 3.Muscularis Externa: –Inner circular & outer longitudinal smooth muscle layers. –The longitudinal layer is not continuous but in the form of 3 ribbons ( teniae coli ). 4.Serosa: –C.T. covered by mesothelium. –Has fat-filled pouches called appendices epiploicae.

16. PRACTICAL SLIDES

17. Fundus of Stomach

18. Duodenum

19. Colon

20. Colon Duodenum