Histology for Pathology Gastrointestinal System and

Exocrine Pancreas

Theresa Kristopaitis, MDAssociate Professor

Director of Mechanisms of Human Disease

Kelli A. Hutchens, MD, FCAPAssistant Professor

Assistant Director of Mechanisms of Human Disease

Loyola Stritch School of Medicine

Objectives• On H&E stained sections, identify the four general layers of the digestive tract

organs (esophagus, stomach, small bowel, colon): Mucosa; submucosa; muscularis externa, and adventitia/serosa

• On H&E stained sections identify the following components of the mucosa: epithelium, lamina propria, muscularis mucosa

• Describe the components of the submucosal layer of the digestive organs• Explain the location of Meissner plexus vs Auerbach plexus and describe the

function of each• Name the type of epithelium comprising the mucosa of the esophagus, stomach,

small bowel, appendix, colon and anal canal.• Identify submucosal glands in the esophagus and describe their function.• Describe the composition of the esophagogastric junction• Name the four parts of the stomach.• Identify gastric pits and explain their function.• On high power H&E stained sections distinguish parietal cells from chief cells. List

the substances secreted by each of the cells.

Objectives• Identify the following key components of the small intestine:• Duodenum: villi, Brunner glands• Jejunum: villi, goblet cells • Ileum: villi, goblet cells, Peyer patches• Define Crypts (or Glands) of Lieberkuhn.• Contrast vili vs plicae circulares• On H&E stained sections distinguish colon from small intestine.• Define taenia coli.• In H&E stained sections of pancreas distinguish the endocrine

components of the pancreas from the exocrine components.• In H&E stained sections of pancreas identify pancreatic acinar cells

vs ducts.

Oral Cavity

• Inner surface of the lips, cheeks, soft palate, surface of tongue, and floor of the mouth– Nonkeratinized stratified squamous epithelium– Lamina propria– Submucosa

• Gingiva and hard palate– Keratinized stratified squamous epithelium– Lamina propria

• Tongue: specialized mucosa with papillae

Digestive Tract• Comprised of hallow organs

– Esophagus– Stomach– Small intestine– Large intestine

• Histologic organization:– Mucosa:

• Epithelium, lamina propria, muscularis mucosa– Submucosa:

• connective tissue, vessels, and Meissners plexuses, some times mucous glands

– Muscularis externa: 2-3 layers of smooth muscle (plus skeletal muscle in esophagus), myenteric (Auerbach) plexus in between muscle layers

– Serosa and adventitia: Outermost layer of loose connective tissue and blood vessels. Call serosa if covered my mesothelium; adventitia otherwise

Esophagus

• Mucosa: non-keratinizing stratified squamous• Submucosa: contains mucous glands – Increased mucous glands at lower esophagus (GE

junction) to protect esophagus from gastric juices

• Muscularis externa: inner circular and outer longitudinal– Contains skeletal muscle fibers

Esophagus Squamous mucosa

Muscularis Externa

Submucosa

Adventitia / Serosa

Mucosa

Muscularis mucosa

Gastric-Esophageal Junction(Esophagogastric junction)

Stomach• Anatomically and histologically divided into

cardia, fundus body, and pylorus– Cardia: first section; separate from esophagus by

cardiac sphincter. Glands contain mucus-secreting cells, stem cells, enterendocrine, and occasional parietal cells

– Fundus and body: largest portion. Fundic glands contain parietal cells and chief cells with some stem cells, mucous cells and enteroendocrine cells

– Pyloric region: lower end that connects to duodenum; ends at pyloric sphincter. Glands primarily mucus-secreting cells and two special endocrine cells: gastrin-secreting (G cells) and somatostatin-secreting cells (D-cells)

Mucosa of the Stomach

Gastric Pit

Columnar Epithelium

Fundic Mucosa

Fundic Gland

Parietal Cells : secrete HCL

Chief Cells : secret zymogen granules containing pepsinogen

Small Intestine• Major site for absorption of nutrients and its mucosa is

made for this!– Villi and microvilli– Glands (crypts) of Lieberkuhn in lamina propria that open into

the mucosa at the base of villi.• Paneth cells with pink granules at the base of the crypts secrete

lysozymes, tumor necrosis factor-alpha, and defensins. – Submucosa with Meissner plexus

• Three sections– Duodenum: Brunner glands (mucus secreting)– Jejunum: long villi and increased goblet cells – no Brunner

glands or Peyer patches – Ileum: Short villi, many goblet cells, and lymphatic nodules in

the submucosa called Peyer patches

Duodenum

Brunner’s Glands

Mucosa

Paneth Cells

Jejunum

GobletCells

Ileum

Peyers patches

Paneth Cells

Small Intestine: Paneth Cells

Small Intestine

Large Intestine• Major site of absorption of water and salts• Mucosa: No villi, gland of Lieberkuhn with many goblet cells and no

paneth cells. • Submucosa: no glands • Muscularis externa: Inner circular muscle plus outer longitudinal

muscle with myenteric (Auerbach) plexus between.– Outer longitudinal muscle creates three narrow bands called tenia

coli. • Four anatomic sections

– Cecum :– Appendix– Colon– Rectum and anal canal

Large Intestine MucosaGoblet Cells

Colon Wall

Mucosa

Submucosa

Muscularis externa (circular portion)

Muscularis Externa

AppendixLymphatic Nodules

Anal -Rectal Junction

Exocrine Pancreas

• Many serous secretory cells (pancreatic acinar cells) form acinar structures.– Cytoplasm contains zymogen granules

• Secretions carried by main duct to join bile duct at the ampulla in the duodenum

Main pancreatic duct and surrounding acini

Pancreatic AciniMain Duct