DIGESTIVE SYSTEM

1
DIGESTIVE SYSTEM

• 3 major components
• Oral cavity.
• Alimentary canal.
• Associated Glands
• Salivary glands.
• Liver.
• Pancreas.

2
Wall of the Alimentary Canal

• Four concentric layers
• Mucosa
• Epithelial Lining
• Simple columnar epithelium (in stomach
  intestine).
• Lamina propria
• Connective tissue.
• It contains mucosal glands.
• Muscularis mucosae
• 2 layers of smooth muscle cells.

3
Wall of the Alimentary Canal

• Submucosa
• Connective tissue containing blood vessels
  nerves. May contain glands (as in duodenum).
• Muscularis Externa
• 2 smooth muscle layers
• Inner circular layer.
• Outer longitudinal layer.
• Serosa
• Connective tissue covered by mesothelium (simple
  squamous epithelium).

4
STOMACH

• It has 4 regions cardia, fundus, body and
  pylorus.

fundus
cardia
body
pylorus
5
Fundus of Stomach

• 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
• Connective tissue containing blood vessels
  nerves.
• NO glands.
• Muscularis Externa
• 3 smooth muscle layers
• Inner oblique.
• Middle circular.
• Outer longitudinal.
• Serosa
• Connective tissue covered by mesothelium.

7
Fundic Glands

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

8
Fundic Glands

• Composed of 5 cell types
• Parietal cells secrete HCl and gastric intrinsic
  factor that helps absorption of vitamin B12.
• Peptic (chief) cellssecrete pepsin.
• Mucous neck cellssecrete mucus.
• Enteroendocrine cellssecrete hormones.
• Stem cells regenerative cells.

9
SMALL INTESTINE

• It has 3 regions duodenum, jejunum and ileum.
• To increase surface area the mucosa has
• Villi.
• Crypts (intestinal glands).

10
Duodenum

• 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

• Submucosa
• Connective tissue containing blood vessels and
  nerves.
• Contains Brunners glands (secrete mucus).
• Muscularis Externa
• 2 smooth muscle layers
• Inner circular layer.
• Outer longitudinal layer.
• Serosa
• Connective tissue covered by mesothelium.

12
Intestinal Glands (Crypts)

• Simple tubular glands that open between villi.
• Composed of 5 cell types
• Columnar cells absorptive.
• Goblet cells secrete mucus.
• Paneth cells secrete lysozyme (antibacterial).
• Enteroendocrine cells secrete hormones.
• Stem cells regenerative cells.

13
LARGE INTESTINE

• It is composed of
• Appendix,
• Cecum,
• Colon (ascending, transverse, descending
  sigmoid),
• Rectum, and
• Anal canal.

14
Colon

• 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 mucosae2 layers of smooth muscle.

15
Colon

• Submucosa
• NO glands.
• Muscularis Externa
• Inner circular outer longitudinal smooth muscle
  layers.
• The longitudinal layer is not continuous but in
  the form of 3 ribbons (teniae coli).
• 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
Fundusof Stomach
Duodenum