1. Histology of Digestive tract
Dr Abubakr H Mossa
MBBS, 27/11/2012

2. Topic outlines.. General organization of GI tract (layers)
Regional features (differences) in the histology of GI tract segments:
Esophagus
Stomach:
Cardia
Fundus (body)
Pylorus
Duodenum
Jejunum
Ileum
Appendix
Colon
Anorectal junction

3. General organization of GI tract (wall)
Mucosa
Submucosa
Muscle layer (muscularis externa)
Serosa or adventitia

5. General organization of GI tract (wall)
Mucosa:
Submucosa
Muscle layer (muscularis externa)
Serosa or adventitia
Formed by three layers;
Epithelium: lining the inside of the lumen. (functions?)
Lamina propria (LP): loose connective tissue. (Contents?)
Muscularis mucosa: thin layer of smooth muscle (inner circular & outer longitudinal) to change the shape of the mucosa.

6. General organization of GI tract (wall)
Mucosa
Submucosa:
Muscle layer (muscularis externa)
Serosa or adventitia
Moderately dense CT contains:
Blood vessels
Lymphatics, lymphoid follicles
Nerves AND MEISSNER’S PLEXUS (parasympathetic ganglia)
May contain glands…

7. General organization of GI tract (wall)
Mucosa
Submucosa
Muscle layer: (muscularis externa)
Serosa or adventitia
Smooth muscle in two layers: inner circular & outer longitudinal (importance?)
Between the two layers, MYENTERIC OR AUERBACH PLEXUS can be identified (motor parasympathetic function)

8. General organization of GI tract (wall)
Mucosa
Submucosa
Muscle layer (muscularis externa)
Serosa or adventitia
In the intraperitoneal organs: serosa (formed by thin CT layer covered by mesothelium)
In extraperitoneal organs: adventitia (thin layer of CT only)

10. Regional histology of GI tract

11. Esophagus Layer Features Mucosa Epithelium
Stratified squamous non-keratinized LP
Thin CT
Muscularis mucosa
Thick Longitudinal layer only
Submucosa
Thrown into fold
Esophageal glands
Muscle layer
Upper 1/3: skeletal
Middle 1/3: smooth & skeletal
Lower 1/3: smooth
Serosa / adventitia
All adventitia except the lower 1 inch

12. Esophagus: GL: glands in the submucosa

14. Cardio-esophageal junction: notice the change in the epithelium from ………… to ………….

15. Stomach: general features
Layer
Features
Mucosa
Epithelium
Simple columnar, contains depressions called gastric pits (lead to the gastric glands) LP
Contains GASTRIC GLANDS
Muscularis mucosa
Two layers
Submucosa
Present
Muscle layer
Three layers: inner oblique, middle circular & outer longitudinal
Serosa
The mucosa and submucosa of the stomach show longitudinal folds called RUGAE which disappear on distention

17. Stomach: regions Three different histological regions:
Cardiac
Fundic (body)
Pyloric
They differ mainly in the arrangement of the gastric glands:;
Cardiac: shallow gastric pits, cardiac glands are coiled & mucus secreting
Fundic: deep gastric pits (1/2 of the LP), fundic glands contain all types of cells (discussed later)
Pylorus: deepest gastric pits (>1/2 of LP), pyloric glands contain all types (but mucus neck cells are more)

18. Stomach: cells
All in the fundic glands!
The simple columnar epithelium (in the epithelium & glands) is composed of six cell types:
Surface-lining cells: thick mucus
Mucous neck cells: lubricating mucus
Regenerative (stem) cells
Parietal (oxyntic) cells: HCl & gastric intrinsic factor
Chief (zymogenic) cells; pepsinogen & gastric lipase
Diffuse neuroendocrine system (DNES) cells (also known as amine precursor uptake and decarboxylation [APUD] and enteroendocrine cells).
In the upper ½ of the gland
In the lower 1/3 of the gland

19. Small intestine; general features
Three parts:
Duodenum: 12 cm
Jejunum: 2 m
Ileum: 3 m
Mucosa & submucosa thrown into circular folds called PLICAE CIRCULARIS (permanent?)
VILLI: finger like mucosal projections (0.5 mm)
Between the villi: the invaginations into the LP form INTESTINAL GLANDS (CRYPTS OF LEIBERKUHN)
Microvilli? Goblet cells?
Cells: refer to the diagram

21. Duodenum Layer Features Mucosa Epithelium Simple columnar LP
Few intestinal glands
Muscularis mucosa
present
Submucosa
BRUNNER’S GLANDS: or duodenal glands
Muscle layer
Present
Serosa / adventitia
Serosa Present (except?)

22. Notice the duodenal glands in the submucosa

24. Jejunum Layer Features Mucosa Epithelium Simple columnar LP
Intestinal glands
Muscularis mucosa
Present
Submucosa
Muscle layer
Serosa / adventitia

25. Jejunum

26. Ileum Layer Features Mucosa Epithelium Simple columnar LP
Intestinal glands & PEYER’S PATCHES (large lymphoid follicles)
Muscularis mucosa
Present
Submucosa
Present (Peyer’s patches may extend into this layer)
Muscle layer
Serosa / adventitia

27. Ileum showing Peyer’s batches

28. Large intestine: general features
Consists of:
Cecum
Appendix
Colon (ascending, transverse & descending)
Sigmoid
Anal canal
Epithelium is simple columnar with plenty of goblet cells
LP occupied by long tubular glands
No plica circularis nor villi
Microvilli present

30. Appendix Layer Features Mucosa Epithelium
Simple columnar with plenty of goblet cells and immune cells LP
Intestinal glands & large lymphoid follicels
Muscularis mucosa
Present
Submucosa
Present (some lymphoid follicles may extend to this layer
Muscle layer
Serosa
The whole lumen can be seen under low power

32. Colon Layer Features Mucosa Epithelium
Simple columnar with plenty of GOBLET CELLS LP
Tubular glands
Muscularis mucosa
Present
Submucosa
Muscle layer
But the outer longitudinal is modified into three bands called TINEA COLI
Serosa / adventitia
Present (except?)

35. Rectum
Similar to the colon except that the folds are longitudinal and the tinea coli are absent

36. Thanks