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Histology of Digestive tract
Dr Abubakr H MossaMBBS, 27/11/2012
Topic outlines..• General organization of GI tract (layers)• Regional features (differences) in the histology of GI tract
segments:– Esophagus – Stomach:
• Cardia• Fundus (body)• Pylorus
– Duodenum– Jejunum – Ileum – Appendix – Colon – Anorectal junction
General organization of GI tract (wall)
1. Mucosa2. Submucosa 3. Muscle layer
(muscularis externa)
4. Serosa or adventitia
General organization of GI tract (wall)
1. Mucosa:2. Submucosa 3. Muscle layer
(muscularis externa)
4. Serosa or adventitia
Formed by three layers;1. Epithelium: lining the inside of the
lumen. (functions?)2. Lamina propria (LP): loose
connective tissue. (Contents?)3. Muscularis mucosa: thin layer of
smooth muscle (inner circular & outer longitudinal) to change the shape of the mucosa.
General organization of GI tract (wall)
1. Mucosa2. Submucosa: 3. Muscle layer
(muscularis externa)
4. Serosa or adventitia
Moderately dense CT contains:1. Blood vessels2. Lymphatics, lymphoid follicles3. Nerves AND MEISSNER’S
PLEXUS (parasympathetic ganglia)
4. May contain glands…
General organization of GI tract (wall)
1. Mucosa2. Submucosa 3. Muscle layer:
(muscularis externa)
4. Serosa or adventitia
• Smooth muscle in two layers: inner circular & outer longitudinal (importance?)
• Between the two layers, MYENTERIC OR AUERBACH PLEXUS can be identified (motor parasympathetic function)
General organization of GI tract (wall)
1. Mucosa2. Submucosa 3. Muscle layer
(muscularis externa)
4. Serosa or adventitia
• In the intraperitoneal organs: serosa (formed by thin CT layer covered by mesothelium)
• In extraperitoneal organs: adventitia (thin layer of CT only)
Regional histology of GI tract
Esophagus Layer Features
Mucosa Epithelium Stratified squamous non-keratinized
LP Thin CT
Muscularis mucosa Thick Longitudinal layer only
Submucosa Thrown into fold Esophageal glands
Muscle layer Upper 1/3: skeletal Middle 1/3: smooth & skeletalLower 1/3: smooth
Serosa / adventitia All adventitia except the lower 1 inch
Esophagus: GL: glands in the submucosa
Cardio-esophageal junction: notice the change in the epithelium from ………… to ………….
Stomach: general features Layer Features
Mucosa Epithelium Simple columnar, contains depressions called gastric pits (lead to the gastric glands)
LP Contains GASTRIC GLANDS
Muscularis mucosa Two layers
Submucosa Present
Muscle layer Three layers: inner oblique, middle circular & outer longitudinal
Serosa Present
• The mucosa and submucosa of the stomach show longitudinal folds called RUGAE which disappear on distention
Stomach: regions
• Three different histological regions:– Cardiac – Fundic (body)– Pyloric
• They differ mainly in the arrangement of the gastric glands:;– Cardiac: shallow gastric pits, cardiac glands are coiled & mucus
secreting– Fundic: deep gastric pits (1/2 of the LP), fundic glands contain all
types of cells (discussed later)– Pylorus: deepest gastric pits (>1/2 of LP), pyloric glands contain
all types (but mucus neck cells are more)
Stomach: cells
• The simple columnar epithelium (in the epithelium & glands) is composed of six cell types:
1. Surface-lining cells: thick mucus2. Mucous neck cells: lubricating mucus3. Regenerative (stem) cells4. Parietal (oxyntic) cells: HCl & gastric intrinsic
factor5. Chief (zymogenic) cells; pepsinogen & gastric
lipase6. Diffuse neuroendocrine system (DNES) cells (also
known as amine precursor uptake and decarboxylation [APUD] and enteroendocrine cells).
All in the fundic glands!
In the upper ½ of the gland
In the lower 1/3
of the gland
Small intestine; general features
• Three parts: – Duodenum: 12 cm– Jejunum: 2 m– Ileum: 3 m
• Mucosa & submucosa thrown into circular folds called PLICAE CIRCULARIS (permanent?)
• VILLI: finger like mucosal projections (0.5 mm) • Between the villi: the invaginations into the LP form
INTESTINAL GLANDS (CRYPTS OF LEIBERKUHN)• Microvilli? Goblet cells?• Cells: refer to the diagram
Duodenum Layer Features
Mucosa Epithelium Simple columnar
LP Few intestinal glands
Muscularis mucosa present
Submucosa BRUNNER’S GLANDS: or duodenal glands
Muscle layer Present
Serosa / adventitia Serosa Present (except?)
Notice the duodenal glands in the submucosa
Jejunum Layer Features
Mucosa Epithelium Simple columnar
LP Intestinal glands
Muscularis mucosa Present Submucosa Present
Muscle layer Present
Serosa / adventitia Present
Jejunum
Ileum Layer Features
Mucosa Epithelium Simple columnar
LP Intestinal glands & PEYER’S PATCHES (large lymphoid follicles)
Muscularis mucosa Present
Submucosa Present (Peyer’s patches may extend into this layer)
Muscle layer Present
Serosa / adventitia Present
Ileum showing Peyer’s batches
Large intestine: general features
• Consists of:– Cecum – Appendix– Colon (ascending, transverse & descending)– Sigmoid – Anal canal
• Epithelium is simple columnar with plenty of goblet cells• LP occupied by long tubular glands • No plica circularis nor villi • Microvilli present
Appendix Layer Features
Mucosa Epithelium Simple columnar with plenty of goblet cells and immune cells
LP Intestinal glands & large lymphoid follicels Muscularis mucosa Present
Submucosa Present (some lymphoid follicles may extend to this layer
Muscle layer Present
Serosa Present
The whole lumen can be seen under low power
Colon Layer Features
Mucosa Epithelium Simple columnar with plenty of GOBLET CELLS
LP Tubular glands
Muscularis mucosa Present
Submucosa Present
Muscle layer Present But the outer longitudinal is modified into three bands called TINEA COLI
Serosa / adventitia Present (except?)
Rectum
• Similar to the colon except that the folds are longitudinal and the tinea coli are absent
Thanks