Gastrointestinal tract

HISTOLOGY OF GASTROINTESTINAL TRACT

Dr. Archana Rani Associate Professor Department of Anatomy KGMU UP, Lucknow
29.04.2015

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 areolar connective tissue

Oesophagus

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.



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

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

Gastro-Duodenal Junction

Small Intestine
It is divided into duodenum, jejunum and ileum. Mucosa: characteristic features- Plicae circularis (valves of Kerkring) Villi & Microvilli Goblet cells (few) Crypts of Lieberkuhn (intestinal glands) Glands are lined by columnar cells, goblet cells, Paneth cells & enteroendocrine cells

Small Intestine

Small Intestine
Submucosa: contains blood vessels, lymphatics and Meissner’s plexus. Muscularis externa: Outer longitudinal and inner circular layers of smooth muscle.Serosa/Adventitia

Duodenum

Presence of Brunner’s glands in submucosa

High power view of the Duodenal Mucosa

Jejunum
Villi are tongue shaped.Absence of Brunner’s glands.


Ileum
Presence of lymphoid aggregations in lamina propria known as Peyer’s patches.Villi are short & finger like.

Large Intestine

It consists of: appendix, colon, rectum and anal canal. Mucosa: Absence of Plicae circulares and villi Presence of Microvilli Presence of Crypts of Lieberkuhn Presence of Goblet cells in large number Submucosa Muscularis externa: Inner circular layer - thin compared to small intestine. Outer longitudinal layer- forms Taenia coli. Adventitia: Appendices epiploicae (peritoneum forms pouch like processes filled with fat)

Large Intestine

Magnified view of a villus

Large Intestine

Vermiform Appendix
A small blind-ending diverticulum. Large accumulations of lymphoid tissue in lamina propria which may extend into submucosa. Intestinal villi are usually absent. Crypts are poorly formed. Muscularis externa is thin. Absence of taenia coli.

Vermiform Appendix

Rectum

Intestinal glands are straight, like test tubes. A continuous coat of longitudinal muscle is present. Absence of taenia. Absence of appendices epiploicae.

Anal Canal

Epithelium: upper part-simple columnar, middle part-stratified squamous non-keratinized, lower part-covered by true skin. Mucosa has characteristic longitudinal folds-Anal columns. Small mucosal folds between the anal columns -Pectinate line. Crypts disappear below this line. Muscularis externa-circular muscle forms involuntary internal anal sphincter.

Ano-rectal Junction

References
1. diFiore’s Atlas of Histology with functional Correlations, 12th Edition.2. Textbook of Human Histology. Inderbir Singh, 1st Edition. 3. Textbook of Histology. GP Pal, 3rd Edition.

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

MCQ
Q3. Plica circularis is a feature of: Oesophagus Stomach Small intestine Large intestine


MCQ
Q4. Taenia coli is present in: Oesophagus Stomach Small intestine Large intestine

MCQ
Q5. Abundant lymphoid tissue in lamina propria is a feature of: Oesophagus Stomach Duodenum Appendix