Histo: Digestive

Front 1

General features of
esophagus, stomach, intestine walls

Back 1

Innermost
1. mucosa
- epithelium + lamina propria)
2. thin muscularis mucosa
3. submcosa
4. extenral muscularis
- inner circular + outer longitudinal sm mm
5. adventitia
- thin CT
- called serosa if covered by simple squamous epithelium (mesothelium of mesentery)
Outermost

More meat subway more apple

Front 2

GI structures

Back 2

Liver, gallbladder,

esophagus
stomach (cardiac, fundic, pyloric)
Small intestines (duodenum, jejunum, ileum)
colon (taenia coli, appendix)

Front 3

Epithlium cells

Back 3

1. simple columnar cells
2. mucous cells
3. parietal cells (stomach)
3. enteroendocrine cells
4. M-cells
5. progenitor cells

Front 4

1. Simple columnar cells

Back 4

Mucosal, epithelium beginning at stomach and intestine

Absorptive functions in intestine with lots of apical microvilli

Front 5

2. Mucous cells

Back 5

Mostly goblet cell with apical mucus droplets.
Colon: goblet cells in entire epithelium surface
Stomach: mucus cells have small dispersed droplets in cytoplasm

Front 6

3. Parietal cells

Back 6

Stomach
1. Esoinophilic cells with lots mitochondria
2. intracellular canaliculi: invaginated membrane surface for:
- HCl secretion
- gastric intrinsic factor (GIF): ileal absorption of B12, co factor in red cell production.

Front 7

4. Enteroendocrine cells

Back 7

Diffuse Neuroendocrine System (DNES)
- many types of cells in secretion, gut motility etc
- e.g. gastrin-producing cells -> stimulate HCL secretion
- argentaffin cells: stai with silver
- APUD (Amine Precursor Uptake And Decarboxylation): metabolic profile in catecholamine production.

Front 8

5. M-Cells

Back 8

Intestinal cells
- uptake and present ingested bacterial antigens to mucosal/submucosal lymphocytes.
- activation of gut asso immune system (GALT)

Front 9

6. Progenitor Cells:

Back 9

- Undifferented cells in glands for renewal
- epithelium replaced 5-7 days
- base of intestinal glands: mitotic figures.

Front 10

Other Layers

Back 10

Brunners: Duodenum's submucosal mucous glands
Peyers Patches: Ileum's large submucosal lymphoid nodules
taenia coli: Colon's bundled arrangement of outer longitudinal mm layer (in addition to mucus cells)

Front 11

Nerves

Back 11

Neural regulation (autonomic): secretion, blood flow, organized mm sm contraction of gut wall

Sympatheic/parasympathetic nerves: penetrate all to form net works of two interconnected concentric plexi

1. Auerbach's plexus (pyloric stomach)
- postganglionic parasympathetic ganglion cells form cluster b/t inner circular and outer longitudinal layers of muscularis externa.
SYM AND PARASYM
2 Meissner's plexus (best seem in jejunum slide)
- mostly submucosal with fibers extend in to mucosa. Parasmpathetic ganglion cells are less conspicuous.


Preganglionic parasympathetic fibers supply cells are derived primary from vagus nerve.

Front 12

Blood supply

Back 12

Branches of segmental vessels: supply each gut reigon an dperforate muscularis to form small arterial branches in submucosa

Submucosal arterioles are source of capillary netowrks extend into mucosal layer.

Lymphatic vessls originate in mucosa drain externally toward muscularis
Lacteals: in small intestine lymphatic channels often visible in core of each villus.

Front 13

Reginal distinction graph and chart

Back 13

p. 122 and 123

Front 14

Esophagus

Back 14

Esophageal mucosa
- stratified squamous (nonkeratinized) epithelium

Small sm mm fiber bundles of muscuarlaris mucosa blend with submucosal CT

Muscles:
1. Upper esophagus 's muscularis externa is skeletal mucles
2. lower esophagus: smooth mm

Esophageal-cardiac junction
- mucous glands
- sharp transition from stratified squamous epithelium to infolded irregular surface with simple glands and cuboidtal mucoid cells
- thickening of muscularis externa forms sphincter-like; prevent acid reflux.

Front 15

Stomach

Back 15

A. Cardiac region: shallow simple mucus glands

B. Fundic stomach
- thickest mucosa traversed by deep epithelial glands
- simple branched glands of 3 zones
1. mucous cells: in clear gastric pits at neck of gland
2. parietal cells: acidophilic H+ secretion, carbonic anhydrase rich, mitochondia, gastric intrinsic factor for B12 absorption
3. Chief: base of glands with basophilic zymogen granules (protease)

C. Pyloric stomach
- shallowe glands
- alveolar cluster of mucus producing cells at base
- secrete basic mucous to neutralize acidic contents before pyloric sphincter into duodenum.

Front 16

General Small intestine cell types and structures.

Back 16

Villi: increase mucosal surface area
Lieberkuhn crypts: glandular invagination between villi
Columnar epithelium: absorptive cells wtih apical microvillin interspered wtih mucous goblet cells

Villi:
1. Lamina propria form a core a loose Ct wtih lumphocytes, plasma cells, polymorphonuclear leukocyes (eosinophils)
2. longest in jejunum (major absorption site)

Cells:
1. progenitor cells: in base of intestinal crypts to typs o fintestinal epithelial cells for rapid turnover (5 days)
2. columnar absorptive cells: microvilus striated border wtih interspered goblet cells
- PAS: stain glycocalyx of microvillus and goblet cells.
3. enteroendocrine (APUD, enterochromaffin, argentaffin): adluminal nuclei with cytoplams and secretory granules positioned toward capillaires in lamina propria.
4. M-cells: dome shaped, GAlT, transport antigens from gut lumen to activate mucosal lymphocytes

Front 17

General Small intestine absorption of metabolites

Back 17

Absoprtion of metabolites
1. microvillus border with glycocalyx (plasma-membrane associated glycoproteins)
2. terminal digestion
- glycocalyx -> adhesion of digested amino acids and sugars, further digested by clycocalyz-associated enzymes
3. Final small molecular products: transprot into capillaries of lamina propia, drain to hepatic portal vein to liver.

Lipids: reduced to free fatty acids, then passively absorbed through intestinal epithlial cell membranes
- converted to triglycerides and conjugated to proteins -> lipoprotein called chylomicra
- chylomicra enter lacteals in core of villy drain to lymphatics, thoracic duct, into systemic circulation via left subclavian vein.

Front 18

General intestine: immunologic defenses

Back 18

Two lines of defense
1. gut lumen, epithelial secreate IgA
2. lamina propria: contain lymphoctes, moncytes, granulocytes

Chonic lymphoid activation
- prominant GALT, active lmphoid nodules in Peyer's patches, appendix, colon

IgA
- antibody dimer link edby J peptide
- dimers coupled to secretory piece, protect antibody against degradation in intestines.
- Lymphocyte produced then secreted into intetines from
1. gut: cross intestinal epithelium itself
2. liver: recovered circulating IgA from blood, secret into bile canaliculi and biliary tract
- enterohepatic circulation: intestinal IgA reabosrbed from ileum and recycled to liver.

Front 19

Intestine

Back 19

Duodenum
1. only region with submucosal glands
2. valves of kierkring: submucosal holds
3. burnner's galnds
- simple alveolar grans proudce alkaline mucous
- protect mucosal surface and neutralize acidic contents
- perforate mscularis mucosa and empty into base of intestinal crypts.

Jejunum
1. longest villi, lack submucosal galnds, prominent submucosal
lymphoids nodules
2. teminal digestion in glycocalyx of absorptive cells and
3. transport of nutrients into villou core -> cap -> venous flow -> liver
4. lipids -> lacteal
5. Not duodenum b/c no brunner's glands; Not Ileum b/c little lymphoid nodules (PPatches)

Ileum:
1. Peyer's patches
2. Paneth cells: clustered at base of each crypt, eosinophilic

Front 20

Large Intestine/Colon

Back 20

1. Mostly goblet cells, closely spaced crypts, more flattened surface
2. outer longitudinal yers: muscularis externa is discontinuous around perimeter form 3 bundles (taenia coli)

Rectoanal junction
- similar epithlium and glandular appearance in mucosa.
- sharp transition stratified squamous, then to keratinized epithelium
- thickened smm mm of internal sphincter
skeletal mm of external sphincter, apocrine sweat glands and hair follicles in perianal regions

hairs/keratinized epithelium - different from esophageal cardiac-junction