1. Histology for Pathology Gastrointestinal System and Exocrine Pancreas
Theresa Kristopaitis, MD
Associate Professor
Director of Mechanisms of Human Disease
Kelli A. Hutchens, MD, FCAP
Assistant Professor
Assistant Director of Mechanisms of Human Disease
Loyola Stritch School of Medicine
Welcome to basic histology of the skin

2. Objectives
On H&E stained sections, identify the four general layers of the digestive tract organs (esophagus, stomach, small bowel, colon): Mucosa; submucosa; muscularis externa, and adventitia/serosa
On H&E stained sections identify the following components of the mucosa: epithelium, lamina propria, muscularis mucosa
Describe the components of the submucosal layer of the digestive organs
Explain the location of Meissner plexus vs Auerbach plexus and describe the function of each
Name the type of epithelium comprising the mucosa of the esophagus, stomach, small bowel, appendix, colon and anal canal.
Identify submucosal glands in the esophagus and describe their function.
Describe the composition of the esophagogastric junction
Name the four parts of the stomach.
Identify gastric pits and explain their function.
On high power H&E stained sections distinguish parietal cells from chief cells. List the substances secreted by each of the cells.

3. Objectives
Identify the following key components of the small intestine:
Duodenum: villi, Brunner glands
Jejunum: villi, goblet cells
Ileum: villi, goblet cells, Peyer patches
Define Crypts (or Glands) of Lieberkuhn.
Contrast vili vs plicae circulares
On H&E stained sections distinguish colon from small intestine.
Define taenia coli.
 In H&E stained sections of pancreas distinguish the endocrine components of the pancreas from the exocrine components.
 In H&E stained sections of pancreas identify pancreatic acinar cells vs ducts.

4. Oral Cavity
Inner surface of the lips, cheeks, soft palate, surface of tongue, and floor of the mouth
Nonkeratinized stratified squamous epithelium
Lamina propria
Submucosa
Gingiva and hard palate
Keratinized stratified squamous epithelium
Tongue: specialized mucosa with papillae

5. Digestive Tract Comprised of hallow organs Esophagus Stomach
Small intestine
Large intestine
Histologic organization:
Mucosa:
Epithelium, lamina propria, muscularis mucosa
Submucosa:
connective tissue, vessels, and Meissners plexuses, some times mucous glands
Muscularis externa: 2-3 layers of smooth muscle (plus skeletal muscle in esophagus), myenteric (Auerbach) plexus in between muscle layers
Serosa and adventitia: Outermost layer of loose connective tissue and blood vessels. Call serosa if covered my mesothelium; adventitia otherwise

6. Esophagus Mucosa: non-keratinizing stratified squamous
Submucosa: contains mucous glands
Increased mucous glands at lower esophagus (GE junction) to protect esophagus from gastric juices
Muscularis externa: inner circular and outer longitudinal
Contains skeletal muscle fibers

7. Esophagus Squamous mucosa Submucosa Muscularis Externa Mucosa
Muscularis mucosa
Adventitia / Serosa

8. Gastric-Esophageal Junction (Esophagogastric junction)

9. Stomach
Anatomically and histologically divided into cardia, fundus body, and pylorus
Cardia: first section; separate from esophagus by cardiac sphincter. Glands contain mucus-secreting cells, stem cells, enterendocrine, and occasional parietal cells
Fundus and body: largest portion. Fundic glands contain parietal cells and chief cells with some stem cells, mucous cells and enteroendocrine cells
Pyloric region: lower end that connects to duodenum; ends at pyloric sphincter. Glands primarily mucus-secreting cells and two special endocrine cells: gastrin-secreting (G cells) and somatostatin-secreting cells (D-cells)

10. Mucosa of the Stomach
Columnar Epithelium
Gastric Pit

11. Fundic Mucosa Parietal Cells : secrete HCL Fundic Gland
Chief Cells : secret zymogen granules containing pepsinogen

12. Small Intestine
Major site for absorption of nutrients and its mucosa is made for this!
Villi and microvilli
Glands (crypts) of Lieberkuhn in lamina propria that open into the mucosa at the base of villi.
Paneth cells with pink granules at the base of the crypts secrete lysozymes, tumor necrosis factor-alpha, and defensins.
Submucosa with Meissner plexus
Three sections
Duodenum: Brunner glands (mucus secreting)
Jejunum: long villi and increased goblet cells – no Brunner glands or Peyer patches
Ileum: Short villi, many goblet cells, and lymphatic nodules in the submucosa called Peyer patches

13. Duodenum
Mucosa
Brunner’s Glands
Paneth Cells

14. Jejunum
Goblet
Cells

15. Ileum
Paneth Cells
Peyers patches

16. Small Intestine: Paneth Cells

17. Small Intestine

18. Large Intestine Major site of absorption of water and salts
Mucosa: No villi, gland of Lieberkuhn with many goblet cells and no paneth cells.
Submucosa: no glands
Muscularis externa: Inner circular muscle plus outer longitudinal muscle with myenteric (Auerbach) plexus between.
Outer longitudinal muscle creates three narrow bands called tenia coli.
Four anatomic sections
Cecum :
Appendix
Colon
Rectum and anal canal

19. Large Intestine Mucosa
Goblet Cells

20. Colon Wall
Muscularis externa (circular portion)
Mucosa
Submucosa

21. Muscularis Externa

22. Appendix
Lymphatic Nodules

23. Anal -Rectal Junction

24. Exocrine Pancreas
Many serous secretory cells (pancreatic acinar cells) form acinar structures.
Cytoplasm contains zymogen granules
Secretions carried by main duct to join bile duct at the ampulla in the duodenum

25. Main pancreatic duct and surrounding acini
Main Duct
Pancreatic Acini