Histo Lecture 14 - Intestines

Front 1

Meissner's plexus

Back 1

Submucosal plexus that contains both parasympathetic and sympathetic innervation

Front 2

Small intestine Function and Key structural features

Back 2

Fctn: digestion and absorption of all nutrients
Key features: highly adapted for maximal surface area:
very long (15-18 feet)
folds of mucosa/submucosa
mucosa has finger-like projections ("villi")
epithelial cells have microvilli

Front 3

What layers make up the intestinal folds?

Back 3

submucosa and mucosa

Front 4

Intestinal crypts

Back 4

AKA crypts of Lieberkuhn, invaginations between villi
Site of secretion of fluids and electrolytes
Stem cells arise here

Front 5

Enterocytes

Back 5

Line intestines
Contain microvilli
One cell thick - easy for diffusion

Front 6

Normal Intestinal Villus/Crypt Height ratio

Back 6

Villus Height = 4,5 x (Height of crypt)

Front 7

What is in/below an intestinal villus?

Back 7

Central core of lamina propria and fibers of muscularis mucosae.
Lympatics, Nerves, Blood vessels,smooth muscle from muscularis mucosi.
Lymphs drain into central lacteal.

Front 8

Paneth cell

Back 8

Triangular, pyramidal cells, very pink
Only found in small intestine
Found in bottom of crypts

Front 9

Intercellular clefts

Back 9

Spaces between enterocytes

Front 10

Dissacharridases: where they at?

Back 10

In the brush border!

Front 11

Path of chylomicrons

Back 11

leave bottom of cell through intercellular clefts, enter branch of lympathics

Front 12

What are morphological differences between villus and crypt cells?

Back 12

Villus: Tall, columnar, well-developed terminal web and microvilli, abundant golgi/ER

Crypt cells: short/cuboidal, rudimentary/minimal terminal web/microvilli, sparse golgi/ER

Front 13

Brunner's glands

Back 13

In submucosa ONLY in duodenum, cells contain alkaline mucus with basal nuclei.

Front 14

Where do bile acids and vitamin B12 get absorbed?

Back 14

Terminal ileum (last 100cm). Can be ulcerated by Chrohn's-- there people could have trouble with bile or B12 reabsorption.

Front 15

Peyer's patches

Back 15

Collections of lymphoid cells/lymphocytes; visible on surgically/endoscopy

Front 16

Large intestine function and key structural features

Back 16

Function: absorption of water, propulsion of feces

Key structural features: mucosa: flat (no villi); mostly goblet cells
muscularis propria: thick; outer layer arranged as three long bands (tenia coli)

Front 17

Cell types in Colon; features

Back 17

Goblet cells
-most prominent cell type, ound, clear cytoplasm w/ mucus and basal nuclei, located throughout crypt, mucus serves as protection and lubrication of stool

Columnar (absorptive) cells
-appearance similar to that of small intestinal enterocytes, but less numerous in colon and with a poorly developed striated border, serves to absorb water/electrolytes

Endocrine cells
-pyramidal cells w/ secretory granules, only a few per crypt, cecum and rectum have the most endocrine cells, secrete hormones (exact fctn unknown)

Paneth cells
-very rare in colon (cecum, ascending colon)

Stem cells
-located near crypt case

Front 18

Internal, external sphincters muscle types

Back 18

Internal is smooth muscle
External is skeletal muscle

Front 19

Reflux esophagitis: endoscopy and histology

Back 19

Endoscopy: Red, linear streaks, exudate
Histology: Basal cell hypertrophy
Thinning of squamous cell layer
extension of papillae
intra-epithelial eosinophils, neutrophils

Front 20

Complications of Reflux esophagitis

Back 20

Esophageal ulcers
Stricture
Columnar metaplasia ("Barrett's Esophagus")

Front 21

Barret's Esophagus: Definition, Origin, Endoscopy, and Histology

Back 21

Definition: columnar epithelium in the esophagus
Origin: GE reflex (vs. incomplete replacement of fetal columnar epithelium)
Endoscopy: Islands/tongues of columnar mucosa
Histology: Gastric type, "specialized" type (intestinal, goblet cells)

Front 22

Etiology of esophageal varices

Back 22

Scarred liver/portal hypertension--> increased pressure in coronary veins in submucosa that drain esophagus --> esophageal varices

Front 23

Gastritis: endoscopy findings

Back 23

Bear-claw red streaks

Front 24

Gastric ulcer: endoscopy findings

Back 24

Deep crater with exudate (healing process). Eats into submucosa.

Front 25

Celiac Disease

Back 25

Gluten-sensitive enteropathy
Etiology: sensitivity to gluten (gliadin); wheat, barley, rye
Location: proximal small intestine more involved than distal
Histology:
villous atrophy, cuboidal epithelium, crypt elongation/hypertrophy, plasma cells in lamina propria, intra-epithelial lymphocytes

Front 26

Abetalipproteinemia

Back 26

Cannot make β-lipoprotein
Cannot repackage fats-- epithelial cells are full of fat

Front 27

Whipple's disease

Back 27

Macrophages eat Whipple's bacillus, build up in villus, and prevents villus from absorbing nutrients into lacteal. Positive for PAS staining.

Front 28

Diverticular disease

Back 28

Herniation of mucosa and submucosa through the muscularis propria
Actually, "pseudo-diverticulum" (only mucosa and submucosa as opposed to all 4 layers)
Forms on the medial and lateral walls of the colon, where the mesenteric arteries course through spaces between the circular smooth muscle.

Front 29

Inflammatory Bowel Disease

Back 29

Ulcerative colitis
-Mucosal ulceration in Colon (i.e. only on the surface)
-always starts in rectum (proctitis)

Chrohn's Disease
-Transmural inflammation: fistulous tracts can burrow through all layers and fistulize
-ileitis
-ileocolitis (affects both ileum, colon)
-colitis

Front 30

Colon cancer: how it begins

Back 30

Starts from polyp, most likely adenomatous polyp
Proliferation of epithelial cells
Tubular adenoma: contains tubules