Histology of GIT Tract

HISTOLOGY OF GASTROINTESTINAL TRACT

Dr. Hammed N. Mousa Assistant Professor Consultant pathologist Department of pathology.

Contents

Oesophagus Stomach Small Intestine Large Intestine

Histology of the Digestive System

Basic Histological Layers:Mucosa:a. Epitheliumb. Lamina Propriac. Muscularis MucosaeSubmucosa:Submucosal plexus“Plexus of Meissner”Muscularis:Myenteric plexus“Plexus of AuerbachSerosa

Histology of the Mucosa

Organ
Epithelium
Mouth
Nonkeratinized Stratified Squamous
Pharynx
Nonkeratinized Stratified Squamous
Esophagus
Nonkeratinized Stratified Squamous
Stomach
Simple Columnar
Small Intestine
Simple Columnar
Large Intestine
Simple Columnar
Anus
Nonkeratinized Stratified Squamous

Histology of the Mucosa

Organ
Folds of the epithelium
Esophagus
none
Stomach
L: Rugae, S: gastric pits
Small Intestine
L: Plicae circulares, Villi S: Crypts of Lieberkuhn, microvilli
Large Intestine
L: Haustra S: Intestinal glands

Histology of the Submucosa

Organ
Specialized structures
Esophagus
Submucosal mucous glands
Stomach
None
Duodenum
Brunner’s glands Ileum
Peyer’s Patches Large Intestine
None

Histology of the Muscularis

Organ
Smooth muscle layers
Esophagus
2, circular and longitudinal
Stomach
3, oblique, circular, and longitudinal
Small Intestine
2, circular and longitudinal
Large Intestine
2, circular and longitudinal

Histology of the Serosa

Organ
Serosa
Esophagus
Adventitia due to the fact that the esophagus is not in a cavity
Stomach
Visceral Peritoneum
Small Intestine
Visceral Peritoneum
Large Intestine
Visceral Peritoneum
Anus
Adventitia

Oesophagus

Mucosa: Stratified squamous non - keratinized epitheliumSubmucosa: contains Meissner’s plexus and oesophageal glandsMuscularis externa: Upper one-third: skeletal fibres Middle one-third: mixed fibres Lower one-third: smooth fibres Adventitia: loose connective tissue

Oesophagus

Stomach
Mucosa:simple columnar epithelium and presence of gastric pits. Stomach is divided into three histological regions on the basis of nature of glands: Cardiac region Fundic region (fundus & body) Pyloric region

Stomach (Cardiac Region)

Mucosa: simple columnar with oval nuclei, mucous secreting cardiac glands in lamina propria. Submucosa: connective tissue. Muscle layer: inner circular, outer longitudinal. Serosa: simple squamous epithelium.

Stomach (Fundic Region)

Mucosa: simple columnar with oval nuclei, presence of gastric glands in lamina propria.

Figure 24–13 The Stomach Lining

Gastric Glands
Found in fundus and body of stomach, extend deep into underlying lamina propria Secrete gastric juice, mucus, and gastrin Each gastric pit communicates with several gastric glands Two types of secretory cells in gastric glands secrete gastric juice: parietal cells chief cells

Stomach (Fundic Region)

Cells of fundic region: Mucous neck cells Parietal (oxyntic) cells Chief (peptic/zymogen) cells Enteroendocrine cells Undifferentiated cells

Cells of fundic region

Cells of fundic region

Gastric Gland cells of Fundus and Body

Parietal Cells Mostly in proximal portions of glands Secrete intrinsic factor and hydrochloric acid (HCl) Chief Cells Most abundant near base of gastric gland: Secrete pepsinogen (inactive proenzyme) Pepsinogen is converted by HCl in the gastric lumen to pepsin (active proteolytic enzyme) Enteroendocrine cells.


Enteroendocrine and APUD cells: - Located in the basal portion of gastric glands - Secretes serotonin, histamine and gastrin. These are endocrine cells which release their products into the blood vessels.

Stomach (Fundic Region)

Submucosa: contains blood vessels, lymphatics and Meissner’s plexus. Muscularis Externa: an inner oblique (absent in pylorus), middle circular and outer longitudinal layer.Serosa: consist of surface layer of flattened mesothelial cells resting on a thin layer of loose connective tissue with blood vessels and lymphatics.

Stomach (Pyloric Region)

Mucosa: pyloric glands in lamina propria & deeper gastric pits extending half the thickness of mucosa. Muscularis Externa: inner circular (thickened to form pyloric sphincter) and outer longitudinal layer. Submucosa & Serosa: same as in fundic part.

Stomach (Pyloric Region)

Pyloric Glands


MCQ
Q1. Stratified squamous non-keratinized epithelium is a feature of: Oesophagus Stomach Appendix Rectum

MCQ
Q2. Deep gastric pits is a feature of: Oesophagus Cardiac part of stomach Fundic part of stomach Pyloric part of stomach