132. GI Histology

Question 1

What are the four general layers of hollow organs?

Answer 1

1. Mucosa (epithelium, LP, MM)
2. Submucosa (loose ct)
3. Muscularis Propria (IC, OL)
4. Serosa/Adventitia

Question 2

What do the four layers of the esophagus look like on histo?

Answer 2

1. Mucosa - strat squamous epithelium, thin loose ct LP, MM
2. Submucosa - fibrous/loose ct with ducts and glands (secrete food lubricants)
3. Muscularis Propria/Externa: ICM, OLM, upper third striated/skeletal (peripheral nuclei), middle third mixed, lower third smooth muscle (crowded nuclei)
4. Adventitia: thin ct around muscle

Question 3

What is unique about the four layers of the stomach on histo? What do functional cells look like?

Answer 3

1. Epithelium: cytoplasmic mucus globules in multiple small vacuoles (gastric foveolar epithelium)
2. Submucosa: loose ct and glands secreting acid/hormones
3. MP: 3 layers: Inner oblique, middle circular, outer lognitudinal
4. Serosa - rugae of stomach

In fundus:
Parietal cells: pink - acid and IF
Chief cells: blue - pepsinogen/lipase
ECF: histamine

Antrum/pylorus
G Cells - brown on gastrin stain (secrete gastrin)

Question 4

With what three ways does the small intestine maximize absorption?

How do you differentiate duodenum, jejunum, and ileum?

Answer 4

1. Plicae circularis: circumferential folds involving submucosa
2. Villi: fingerlike projections of mucosa
3. Microvilli: fingerlike protrusions of enterocyte (simple columnar epithelial cell) apical plasma membrane

Duodenum: Brunner glands (mucus producing glands - Goblet cells line vili, produce mucin)
Jejunum: no Peyer’s patches and no Brunner glands; tall villi:crypt ratio 1:4 (more crypts than villi)
Ileum: Peyer’s patches: lymphoid follicles

Question 5

What are the two types of cells in crypt epithelium?

What are the cells in villi epithelium?

What are unique features of the small intestine submucoa and muscularis externa?

Answer 5

Crypts:

1. Endocrine cells (purp nuclei on top, red granules on base)
2. Paneth cells: (purp nuclei on base, red granules on top) antibacterial - regulate gut flora

Villi:
Simple columnar epithelium of enterocytes and goblet cells

Submucosa: Meissner’s Plexus: parasymps for glandular secretion

Muscularis: Auerbach’s plexus: parasymps for muscular contraction (between ICM/OLM)

Question 6

What are unique features of the colon?

Cells in mucosa and muscularis externa

Answer 6

No villi
Abundant goblet cells (need for more lubrication)
Teniae coli: 3 longitudinal muscle bands
LP: inflammatory cells b/w crypts

Epithelium: scattered goblet cells, columnar absorptive cells, deep crypts no villi
LP: inflammatory cells

Muscularis Externa: ICM/OLM, Auerbach’s plexus for pararsymp peristalsis/contraction

Question 7

What are the zones of hepatic lobules? Which is more prone to ischemia?

What is the cell type lining bile ducts?

What stains show fibrosis?

Answer 7

Zone 1 outermost - O2/nutrient rich (periportal)
Zone 3 innermost - most vulnerable to ischemia (centrilobular)

Bile ducts: simple cuboidal lining

Reticulin stain: fibrosis= gray
Trichrome stain: hepatocytes red, fibrosis blue (portal tract has collagen, normally looks blue)

Question 8

What are key histo features of the gallbladder?

What is the cell type lining common bile duct?

Answer 8

1. GB: simple columnar epithelium, LP, NO MM/SUBMUCOSA
2. Irregular collections of smooth muscle
3. Brush border microvilli on epithelium
4. Rokitansky-Aschoff Sinuses (invaginations of epithelium)

CBD: simple columnar epithelium with surrounding smooth muscle and adventitia

Question 9

Pancreas histo: what do acini look like? What types of endocrine islets of langerhans are there?

Answer 9

Acini: 80% pancreas by volume, full of zymogen granules around ducts

B Cells: produce insulin (increase glu uptake into cells)
A Cells: produce glucagon (increase glu circulation)
D Cells: produce somatostatin (decrease insulin/glucagon/exocrine pancreas secretion)