The document summarizes the histology of the gastrointestinal tract. It describes the four layers of the GI tract wall - mucosa, submucosa, muscularis, and serosa. It then focuses on specific structures of the stomach, small intestine, and pancreas. Key points include the four regions of the stomach, gastric glands and their role in digestion, villi and crypts in the small intestine, and acini and islets of Langerhans in the pancreas that produce digestive enzymes and hormones. Clinical correlations are provided regarding conditions like atrophic gastritis, pernicious anemia, and acute pancreatitis.

1. Histology of gastrointestinal tract
Mbbs 2nd year
08/09/2013

2. Digestive system consist of the digestive tract and its
associated glands that helps in process of digestion.

3. The gastrointestinal tract is a hollow tube with
lumen of variable diameter .
Wall made up of 4 layers
Mucosa
Submucosa
Musularis
Serosa

5. • Muscle layer : inner :circular outer
longitudinal
• Myenteric nerve plexus (Auerbach)
Musuclaris
• Thin layer of connective tissueSerosa
• Epithelial lining
• Lamina propria
• Muscularis mucosa
mucosa
• Connective tissue
• Submucosal plexus of autonomic
nerve (meissner)
submucosal

7. Stomach is divided into 4 regions : cardia
, fundus , body and pylorus .
Stomach digests the food
by muscular activity
converting it into chyme .

8. The muscularis consist of three layer for mixing of
stomach content and turns into chyme

9. Esophagogastric
junction
Stomach consist of
simple columnar
epithelium that
invaginates into lamina
propia forming gastric
pit .
Emptyping into this pit
are glands .

10. Regions of stomach

11. Glands in cardiac & pylorus
Branched tubular with coiled secretory portion
Responsible for secretion of mucus and lysozyme

12. Body/fundus

13. Gastric gland

15. Clinical correlate :
• In case of atrophic gastritis both parietal and
chief (Zymogenic/Peptic ) cell decrease in
number and results in vitamin B12 deficiency .
• Pernicious anaemia , which is a disorder of
erythrocyte forming mechanism is caused by
lack of IF , and Vitamin B12.

17. Small intestine

18. Small intestine /duodenum
Plica circularis : mucosa
&submucosa
Villi : epithelium &
lamina propria
Microvilli : apical
cytoplasm

19. Mucosa
Surface epithelium : enterocytes & goblet cells
Lamina propria :
Muscularis :
Surface epithelum & lamina propria : villi
Between villi are openings of short tubular glands :
intestinal crypts or crypts of liberkuhn

20. Villus contain microvasculature and lymphatics called
lacteals .

21. Intestinal gland or crypts of liberkuhn
• Goblet cells
• Paneth cells
• Enteroendocrine cells
• Stem cells

22. Submucosa has large clusters of branched tubular mucous
gland , the duodenal gland or brunner gland .

23. Pancreas

24. • Mixed exocrine and endocrine gland
• Produces both digestive enzymes and
hormones .
• Digestive enzymes : exocrine portion
• Hormones : endocrine epithelial cells

25. Pancreatic acini

27. pancreas

28. Islet of
langerhans
Alpha cells : periphery secrete glucagon
Beta cells : centre , secrete insulin
Delta cells : periphery , secrete gastrin and somatostatin

29. Clinical correlate
In acute necrotizing pancreatitis, the
proenzymes may be activated and digest the
whole pancreas, leading to very serious
complications. Possible causes are
alcoholism, gallstones, metabolic
factors, trauma, infection, and drugs.

30. Clinical correlate
Acute pancreatitis :
Damage to the pancreatic acinar cells releases
pancreatic enzymes into the local tissues. These
powerful enzymes cause death of pancreatic tissue
and severe inflammation termed acute
pancreatitis. The release of pancreatic lipase causes
death of local fat cells (fat necrosis). Pancreatic
amylase is released and can be detected at high
levels in the blood. This is a severe life-threatening
condition.