Histology of the upper Git

Objectives By the end of this lecture, the student should be able to discuss the microscopic structure in correlation with the function of the following organs: 1) Esophagus. 2) Stomach.

Alimentary Canal Is the tubular portion of digestive system. Is subdivided into: esophagus, stomach, small intestine (duodenum, jejunum and ileum), and large intestine (cecum, colon, rectum, anal canal, and appendix).

General Architecture of L/M Structure of Alimentary Canal

General Architecture of L/M Structure of Alimentary Canal Serosa

ESOPHAGUS Four concentric layers: Mucosa: Epithelial Lining: Non-Keratinized Str. Squamous Epith. Lamina propria: C.T. containing blood vessels, nerves and lymphatic vessels (Peyer’s patches) Muscularis mucosae: Few layers of smooth muscle fibers. Serosa

Esophagus Submucosa: Connective tissue containing blood vessels, nerves, glands & Meissner’s plexus of nerve fibers and nerve cells. Muscularis Externa: Usually 2 smooth muscle layers: Inner circular layer. Outer longitudinal layer. Auerbach’s (myenteric) plexus in between the 2 layers Serosa or adventitia: Serosa is C.T. covered by mesothelium (simple squamous epithelium) in the abdominal part of the esophagus. or adventitia if there is no mesothelium. Serosa

STOMACH It has 4 regions: cardia, fundus, body and pylorus. Mucosa has folds, known as rugae that disappear in the distended stomach. fundus cardia body pylorus

Fundus of Stomach Mucosa: modify to form fundic glands. The surface epithelium is simple columnar mucus-secreting cells. Submucosa: Connective tissue containing blood vessels & nerves. NO glands. Muscularis Externa: Three smooth muscle layers: Inner oblique. Middle circular. Outer longitudinal. Serosa: C.T. covered by mesothelium.

Mucosa of Fundus of Stomach It is composed of: 1. Surface Epithelium. 2. Fundic glands. 3. Lamina propria: invaded by numerous fundic glands. 4. Muscularis mucosae.

Fundic Glands Fundic glands have: Short pits—one fourth of mucosa. Simple or branched tubular glands. Are rich in parietal & chief cells.

Fundic Glands Composed of 6 cell types: Parietal cells: secrete HCl and gastric intrinsic factor that helps absorption of vitamin B12. Peptic (chief) cells: secrete pepsinogen. Mucous neck cells: secrete mucus. Enteroendocrine (DNES) cells: secrete hormones. G cells : secrete gastrin Stem cells: regenerative cells.

Parietal and Chief Cells 1- Parietal cells 2- Chief cells 1 2

PYLORUS OF STOMACH Mucosa: modify to form pyloric glands. The surface epithelium is simple columnar mucus-secreting cells. Submucosa: Connective tissue containing blood vessels & nerves. NO glands. Muscularis Externa: Two smooth muscle layers: Inner circular. Outer longitudinal. Serosa: C.T. covered by mesothelium.

Pyloric glands Their pits are deep --- about half the length of mucosa. They are branched and convoluted --- many cross sections. The predominant cells are mucous neck cells that secrete mucus.

Clinical Application 1. Hiatus Hernia Definition: It is herniation of the stomach into the thoracic cage through a gap in the diaphragm around the wall of the esophagus. Background: As the esophagus passes through the diaphragm, it is reinforced by the muscle fibers of the diaphragm. In some people, development is abnormal, causing a gap in the diaphragm around the wall of the esophagus.

Clinical Application 2. Barrett’s Syndrome Definition: It is probably a pre-cancerous (pre- malignant) condition due to gastro-esophageal reflux, leading to the replacement of part of the stratified non-keratinized squamous epithelium of the lowest region of the esophagus (at least 3 cm) by a simple columnar epithelium (metaplasia). Treatment: Esophageal resection of the metaplastic part.

3. Gastric Intrinsic Factor Clinical Application 3. Gastric Intrinsic Factor Background: Gastric intrinsic factor (IF) is secreted by parietal cells in gastric glands. It is necessary for vitamin B12 absorption from the ileum. Effect of absence of gastric IF: it results in deficiency of vitamin B12 with consequent development of pernicious anemia.

Clinical Application 4. Atrophic Gastritis Effect of Atrophic Gastritis: Both parietal and chief cells are much less numerous → the gastric juice has little or no acid or pepsin activity.

Clinical Application 5. Peptic Ulcer Definition: a circumscribed ulceration of the gastro- intestinal mucosa extends to the submucosa and may include the muscle layer, occurring in areas exposed to acid and pepsin and most often caused by Helicobacter pylori infection. NB: Gastric erosion: Damage of the gastro-intestinal mucosa that is not penetrating the muscularis mucosae. Types of peptic ulcers: Gastric peptic ulcer. Duodenal peptic ulcer: especially in the 1st part of duodenum.

Causes of peptic ulcer: Helicobacter Pylori (H. Pylori): this type of bacteria is responsible for most of ulcers (70-90%) Non-steroidal anti-inflammatory drugs (NSAIDs): Long term use of these pain relievers is the second most common cause of ulcers e.g. Ibuprofen, aspirin Pathogenesis: Break-down of the thin protective layer of mucus over the surface of epithelial cells leads to damage of the gastric mucosa by the gastric acidity. Complications of peptic ulcer: Perforation of the wall of the stomach → peritonitis. Malignancy (in gastric peptic ulcer). Bleeding .

“The End ” Thank you