Histology LaboratoriesMolecules to Systems

2003Compiled by

James D. Jamieson, MD/PhDThomas L. Lentz, MD

No part of this image collection may be distributed outside of the Yale University Intranet.

Alberts, B. et al. Molecular Biology of the Cell. 4th Edition, Garland Science, New York, 2002.Gartner, L. P. and Hiatt, J. L. Color Atlas of Histology, Williams & Wilkins,

Baltimore, 1994.Kerr, J. B. Atlas of Functional Histology. Mosby, London, 1999.Kessel, R. G. and Kardon, R. H. Tissues and Organs: a text-atlas of scanning

electron microscopy. W. H. Freeman, San Francisco, 1979.Lentz, T. L. Cell Fine Structure. W. B. Saunders, Philadelphia, 1971.Lodish, H. et al. Molecular Cell Biology. W. H. Freeman, New York, 2000.Mizoguti, H. Color Slide Atlas of Histology. Nihon Shashin Shinbunsha, Tokyo.Young, B. and Heath, J. W. Wheater’s Functional Histology. Churchill

Livingstone, Edinburgh, 2000.Micrographs taken by George Palade, Marilyn Farquhar, James D. Jamieson,

Nicolai Simionescu, Maya Simionescu, David Castle, Thomas L. Lentz.

Web Resourceshttp://info.med.yale.edu/webpath/webpath.htmCushing Library Educational Software/Cell Biology/Several Histology Resources

AcknowledgementsSources of Micrographs, Diagrams and Figures

GI Tract I LaboratoryEsophagus, Stomach and Small Intestine

I.GENERAL FUNCTIONS OF THE GASTROINTESTINAL SYSTEM

The main function of the gastrointestinal system is to provide theappropriate conditions for processing foodstuffs into molecular species forabsorption into the circulation as follows:

A. D igestion and Absorption: digestion in bulk in the lumen of the gut(stomach/gastric gland secretions and small intestine/pancreaticsecretions) and local hydrolysis at the microvil lar surface followedby selective absorption across enterocytes into the circulation via theportal vein and liver or into lymphatics (lipids).

B. Transit: the ordered series movement of material through the tractcarried out by its smooth muscle layers. a by endogenous nerves andthe gut endocrine system.

C. Homeostasis: production of factors maintaining homeostasis of thegut lumen e.g., mucus; antibacterial agents/Paneth cells; secretoryIgA (Gut Associated Lymphatic Tissue).

(Stomach and large intestine pattern)

(Small intestine pattern)

II. GENERAL STRUCTURAL FEATURES OF THE GI TRACT

Follows a general plan in entire gastrointestinal tract with four concentriclayers:

1. Mucosa (a) lining epithelium(b) lamina propria(c) muscularis mucosa

2. Submucosa

3. Muscularis externa

4. Serosa (except where viscus is retroperitoneal; external layertermed adventitia).

LANDMARKS IN THE GASTROINTESTINAL TRACT

Gut Segment Mucosa Submucosa Muscularis

Esophagus Stratified squamous Striated m. inepith. (non-keratinized) upper third;

smooth m. inlower third;mixed in mid.

Stomach Absence of villi and Triple-layeredgoblet cells; gastricpits and glands

Duodenum Villi; mucosal glands Brunner'sGoblet cells + glands

Jejunum Villi; mucosal glands PlicaeGoblet cells ++ circulares

Ileum Villi; mucosal glandsPeyer's patchesGoblet cells +++

Colon No villi; mucosal glands; Outer coatGoblet cells ++++ arranged in three

longitudinal bundles(taeniae coli)

Laboratory on the Gastrointestinal Tract I:Oral Cavity Through Small Intestine

Basic Histological Organization and Abbreviations:

Four layers

1. Mucosa (M): epithelium (E) + lamina propria (LP) + muscularis mucosa (MM)

2. Submucosa (SM): thick connective tissue layer with blood vessels, lymphatics, nerves

3. Muscularis externa (ME): striated in upper part of esophagus; inner circular (IC), outer longitudinal (OL)

4. Serosa (S) :squamous epithelium (where absent = adventitia)

LANDMARKS IN THE GASTROINTESTINAL TRACT

Gut Segment Mucosa Submucosa Muscularis

Esophagus Stratified squamous Striated m. inepith. (non-keratinized) upper third;

smooth m. inlower third;mixed in mid.

Stomach Absence of villi and Triple-layeredgoblet cells; gastricpits and glands

Duodenum Villi; mucosal glands Brunner'sGoblet cells + glands

Jejunum Villi; mucosal glands PlicaeGoblet cells ++ circulares

Ileum Villi; mucosal glandsPeyer's patchesGoblet cells +++

Colon No villi; mucosal glands; Outer coatGoblet cells ++++ arranged in three

longitudinal bundles(taeniae coli)

Diagnostic characteristics of the gastrointestinal tract

The following are some of the prominent differences between regionsof the gastrointestinal tract. If you can observe these differences you shouldbe able to distinguish all regions.

Esophagus: Stratified squamous epithelium; mucous glands in the submucosa.Striated muscle in the upper portions of the muscularis externa; smoothmuscle in the lower portion.

Stomach : Simple columnar epithelium arranged to form gastric pits and threetypes of glands. Thick, three-layered muscularis externa. No Villi.

Cardia: Cardiac Glands tend to be convoluted and are lined exclusively bypale staining mucous secreting cells.

Body: Glands of the body are rather straight with limitedbranching and arelined by a smaller population of parietal and chief cells.

Pylorus: Glands of the pylorus posess deeper pits and their basal portions aremore highly coiled and branched than elsewhere in the stomach. Thebasal portion of the glands consist mainly of mucous secreting cells andnumerous endocrine cells.

Small Intestine : Simple columnar epithelial cells with brush borders and gobletcells; villi and crypts of Lieberkühn.

Duodenum: Brunners glands in submucosa. Long villiJejunum: Thin walled, plicae circulares most prominent. Contains a few

goblet cells.Ileum: Peyers patches in submucosa; more goblet cells.

Large Intestine : (Colon) No villi. Goblet cells are found neither in the gastric pitsnor glands, but are found regularly in the colic crypts.

Appendix : Resembles colon but its crypts are not so regularly spaced andare often missing all together. Numerous lymphatic nodules arescattered throughout the lamina propria and reach into the submucosa.

Gall Bladder : Tall columnar cells with many irregularly shaped villi.

Esophagus to Stomach

E

MMSM

ME

IC

OL

M

Esophagus: stratified squamous non-keratinized epithelium; striated muscle in upper 1/3.

LP

Adventitia

E (stratified squamous non-kearatinized)

MM

SM

Submucosal glands

Esophagus

LP

Esophageal - Gastric Junction

Examples of Regional Variations

Esophagus: Stratified Squamous Epithelium

E

MMSM

ME

IC

OL

M

Stomach: Glands Invaginate into Lamina Propria; No Villi; No

Goblet Cells

E

MM

SM

ME

M

Folds - rugae Simple glands extending to MM

Jejunum: Outoldings of Mucosa on SM; Villi; Goblet Cells Present

E

SM

ME

MM

Folds of submucosa = plicae circulares

Villi projecting from plicae

M

M

Ileum: Villi; Fewer Plicae; More Goblet Cells; Peyer’s Patches Prevalent

MM SM

ME

M

Peyer’s patches

VilliCrypts in LP

Mesentery Serosa

Large Intestine: No Villi; Many Goblet Cells;

Simple Glands Extending to MM

Crypts/colonic glands

MM

SM

ME

M

Lymphoid follice

Tongue

Skeletal (striated) muscle fascicles

Stratified squamous epithelium Vallate papilla

Vallate Papilla

Taste buds

Taste Buds on Papilla

Lingual Tonsil

Germinal centers in lymphoid follicles

Sublingual glands

Parotid Gland

Serous exocrine secretory units (amylase)

Myoepihtelial cells/contractile

Mucous

Serous demilune

Submandibular Gland(mixed mucous/serous

Stomach and Gastric Glands

Function of Stomach in Lumenal Digestion

1. Secretion of acid by parietal cells: provides pH of ~1.4 for autoactivation of pepsinogen. Glands in body of stomach.

2. Provides correct pH for action of pepsinogen on proteins.

3. Secretion of pepsinogen by chief cells in glands in body.

4. Secretion of gastrin into circulation from base of glands in pyloric glands in response to stomach contents (alkaline pH; peptides). Gastrin stimulates release of histamine from ECL cells that in turn stimulates acid secretion from parietal cells.

5. Secretion of mucous to protect gastric epithelium.

6. Secretion of intrinsic factor by partietal cells.

(Stomach pattern)

Muscularis Externa of Stomach

Stomach: Glands Invaginate into Lamina Propria; No Villi; No Goblet Cells

E

MM

SM

ME

M

Folds - rugae Simple glands extending to MM

Cardiac Mucosa: Mucous secreting cells only

Gastric pits

MM

LP

Surface mucous cells

Glands

Body (corpus) Mucosa: Surface mucous cells, chief, parietal, and ECL cells.

Gastric pits

MM

Glands

Pyloric (antral) Mucosa: Mucous cells and Gastrin endocrine

Gastric pits

SM

GlandsLymphoid tissue

Surface Mucous Cells: Common to All Regions

Gastric Pit

Gastric GlandBody of Stomach

Body of Gastric Mucosa

Pit

Isthmus

Neck

Base

LP

Parietal cells

Chief cells

Parietal Cells H&E

LPParietal cells

Chief Cells H&E

Secretory granules containing pepsinogen

Lumen of gastric gland

Parietal Cells (thin epoxy section)

LPParietal cells

Intracellular canaliculus

Lumen of gastric gland

Chief cell

LPBlood vessel

Parietal Cells (EM)

Mitochondria

Intracellular canaliculus

Pyloric Antral Glands

Pits

MM

Glands

LP

Pyloric Antral Glands: Immunostained for Gastrin *

*

*

*

Lumen of pyloric gland

Gastin Cell in Base of Pyloric Antral Gland

Secretory granules in endocrine “G” cell containing gastrin

Regulation of Acid Secretion from Parietal Cells

Function of Salivary, Biliary, and Pancreatic Secretions in Lumenal Digestion

Pancreatic secretions:

Centroacinar/small duct cells: Watery secretion rich in HCO3 pH 7.4; neutralizes acid gastric content in duodenum.

Provides correct pH for activation of trypsinogen by microvillar protease = enterokinase > cascade activation of pancreatic proenzymes. Stimulated by secretin released from gut wall in response to low luminal pH

Function of Salivary, Biliary, and Pancreatic Secretions in Lumenal Digestion: continued

Pancreatic secretions:Acinar cells: exocytosis into pancreatic duct of enzymes and proenzymes for digestion; stimulated by CCK which is released from gut wall in response to L amino acids and fatty acids in duodenum.

Proteins: trypsinogen, chymotrypsinogen, proelastase, procollagenase (all activated by trypsin in gut lumen after activation of tyrpsinogen by enterokinase; inactive as secreted).

Carbohydrates: amylase.

Lipids: Prophospholipase, lipase, cholesterolesterase.

Nucleic acids: RNAse, DNAse.

Function of Salivary, Biliary, and Pancreatic Secretions in Lumenal Digestion: continued

Bile:

Bile salts: detergents for emulsification of lipids into water soluble forms for digestion by lipases etc. Synthesized from cholesterol.

Secretory IgA: protection of gut lumen.

Bile pigment: waste from RBC destruction (bilirubin).

Duodenum

Small intestine pattern)

Diagram of Duodenum

Duodenum: Characteristic Brunner’s glands in LP and SM

ME

MM

Villi

SM

Brunner’s glands

Duodenum(PAS stain)

Brunner’s gland

Duct from Brunner’s gland into gut lumen

Lymphoid follicle

Jejunum

Diagram of Jejunum and Ileum

Jejunum: Prominent plicae circulares; villi on plicae; goblet cells more common

E

SM

ME

MM

Folds of submucosa = plicae circulares

Villi projecting from plicae

M

M

Ileum

Ileum: villi; fewer plicae; more goblet cells; Peyer’s Patches prevalent

MM SM

ME

M

Peyer’s patches

VilliCrypts in LP

Mesentery Serosa

Ileum ME

Peyer’s patches with lymphoid follicles

Germinal center

LP

Villi

Crypts

SM

Dome with M cells

Ileum

Peyer’s patch with lymphoid follicles

Germinal center

LP

Villi

Crypts MM

Site of M cells

Transcytosis across intestinal epithelium

The Enterocyte

SEM of Intestinal Villi

Intestinal Villus

LP

Lymphatic vessel

Brush border/microvilli on enterocytes

Goblet cells

Blood vessel

Smooth muscle bundle

Cells of immune system

Villous Core LS

LP

Lymphatic vessel

Brush border/microvilli on enterocytes

Goblet cell

Smooth muscle bundle Blood vessel

LP

Lymphatic vessel(lacteal)

Brush border/microvilli on enterocytes

Goblet cell

Villous Core XS

Capillary

Lymphocytes and plasma cells

EM of Enterocyte

Surface of Enterocyte

Microvilli

Junctional complex

Junctional Complexes Between Enterocytes

Junctional Complexes Between Enterocytes; Freeze Fracture

Brush Border on Enterocyte

Goblet cell

Enterocytes

Brush border

Terminal bar

Microvilli LS

Junctional complex between enterocytes

Microvilli XS

Actin cores

Epithelial Renewal and Gut Protection

Cell Renewal in Gut

Villi and Crypts

Villi

Crypts

LP

MM

Mitoses in crypt in jejunum (*)

*

*

**

Base of Crypts Paneth Cells

Lumen of crypt of Lieberkühn

LP

Paneth cells

Some pathology to think about.

Barrett’s esophagus. Consequence of chronic acid reflux GERD). The stomach would be to the right of the field. What type of mucosa is Barrett’s? what does this tell you about stem cells? Precancerous lesion. What would you do?

Helicobacter pylori. Common cause of gastric ulcers. Where are these bacteria located? How would you treat the problem?

Celiac sprue. 1:2000 Caucasians; genetic. Note flattened epithelium and shortened villi compared to normal intestine on left. What symptoms might these changes cause?

Crohn’s disease (Ulcerative colitis). What layer of the intestinal wall is

affected? What symptoms can you predict based on the histology?

Crohn’s disease. Higher power. What are the blue staining cells in the lamina propria? What does this tell you?