GI/L Histology Flashcards by Nadim Chowdhury

LIP 1

mucosa = typical of mouth (stratified squamous non-keratinising epithelium - SSNKE)
@ margin, abrupt transer to skin (stratified squamous keratinising epithelium - SSKE)
connective tissue (sub-mucosa) - collage and elastin
deeper layers - glands and striated skeletal muscle (change shape of oral cavity)
small blood vessl @ sub-mucosa help keep moist

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LIP 2: TRANSITION

SSNKE (lower) to SSKE (upper)

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LIP 3

inner lip: SSNKE
small clumps of salivary tissue
sebaceous glands (Fordyce’s spots) open to surface rather than hair follicles

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HAIR FOLLICLE

on keratinised surface of lip

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TONGUE 1

SSNKE on ventral (lower) surface
SSKE on dorsal (upper) surface - constant abrasion
coarse multi-directional skeletal muscle bundles

extrinsic fibers - skeletal muscle inserted to lower jaw

intrinsic fibers - skeletal muscle inserted to fibrous connective tissue underlying mucosa

mixed sero-mucous salivary glands (SUBLINGUAL)

lymph nodules - particularly @ posterior 1/3 of tongue (linguinal tonsisl)

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TONGUE - UPPER SURFACE

SSKE
connective tissue
2 types of salivary glands
large bundles of striated muscle

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TONGUE - SEROUS GLANDS

more pink staining (darker than mucous)
small serous salivary glands
acini - clusters of grapes
nucleus on base

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MUCOUS GLANDS

small salivary mucus gland
michael palin = mucus pale*

mucus glands stain paler than serous!

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PAPILLAE AND TASTE BUDS

dorsal tongue surface - complex folds = papillae

sweet (tip) / slaty (front/side) / sour (further back) / bitter (whole back)

filiform papillae (threadlike) - most common, tall, pointed - @ whole anterior 2/3

fungiform papillae (mushroom-like) @ tip and sides

@ lateral side fungiform papillae = pale-staining, spindle-shaped taste buds w/ nerves/synaptic vesicles

circumvallate papillae (V-shaped row) @ divide between anterior 2/3 and post. 1/3

this slide - 2 paler staining taste buds embedded in opposing sides of adjacent fungiform papillae

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NERVES OF TONGUE

small nerves lying in sub-mucosa of tongue
supple close by taste buds

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PAROTID SALIVARY GLAND (SEROUS ONLY)

striated duct (top left)
surrounded by serous acini
synthesise alpha-amylase
secreted via ducts to mouth
ducts can alter ionic concentrations

branches of facial nerve pass through gland
large lymph nodes embedded within gland

secretory cells - pyramidal, spherical nucleus, basal cytoplasm full of rER, apex contains prominent secretory granules (pink staining)

duct cells - simple cuboidal (stratified at distal end)

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PAROTID GLAND 2

C (bottom) = nerve
D = large lymph node

inset - close up of lymph node

parotid saliva contains IgA (from plasma), combines with proteinous pieces so reaches intestine unmodified by amylase

striated duct - from invaginations, indicative of water reabsorption

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SUBLINGUAL SALIVARY GLAND (MAINLY MUCUS)

pale staining secretory cells
darker staining duct w/ simple cuboidal epithelium
flattened oval nuclei to base of cells
branched tubular acinar glands
sticky mucus rich secretion

major constiuent - polysaccharide

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PSNS (parasympathetic nervous system) GANGLION

PSNS ganglion
many nerve cell bodies
involved heavily in secretion regulation

this slide = sublingual

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SUBMANDIBULAR SALIVARY GLANDS (MIXED)

well defined / globular
branched tubulo-acinar
interspersed with fat adipose
mixed secertion - part mucus, part enzyme rich

demi-lunes - serous cells form demi-lunes (half-moons) at closed ends of tubules

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LYMPH NODULE WITHIN SUBMANDIBULAR GLAND

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EPIGLOTTIS

@ posterior of tongue
boundary of oropharynx and laryngeal pharynx
mostly SSNKE
lower part posterior - pseudo-stratified columnar ciliated epithelium (respiratory)

contains:

elastic cartilage plate
lymph nodules (submucosa)
salivary glands (submucosa)

Box A = buccal surface - faces mouth

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EPIGLOTTIS 2

SSNKE

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GI FORMATIVE 1

this is a tastebud surrounded by squamous epithelium

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GI FORMATIVE 2

mucus acini
basally located nuclei
ducts lined by cuboidal/columnar epithelium

this is a sublingual gland

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GI FORMATIVE 3

serous glands @ bottom
mucus glands @ top
this is mixed

therefore this is a submandibular gland

(mixed = submandibular)

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GI FORMATIVE 4

this is purely serous (granules)

this is parotid gland

therefore contains branches of facial nerve

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GI TRACT LAYERS (x4)

mucosa - innermost. epithelium (folded), connective tissue (lamina propria - w/ lymphoid tissue), smooth muscle ring (muscularis mucosa)
sub-mucosa - loose connective tissue, glands and lymphoid tissue, many blood vessels, meissner’s plexus (enteric nervous sytem)
external muscle coat (muscularis externa)- 2 layers of smooth muscle - persistalis -auerbach’s plexus (enteric nervous system)
serosa - simple squamous epithelium

OSEOPHAGUS

mucosa:

SSNKE
thin lamina propria
narrow muscularis mucosa (thicker @ gastric end)

below diaphragm:

simple columnar epithelium (same as gastric region of stomach)
site of pathological change - Barrett’s oesophagus!

sub-mucosa: sero-mucous glands (lubrication), large thin-walled veins (@ distal end - oesophageal variscosities)

muscularis externa:

upper 1/3 = skeletal / middle 1/3 = mixed / lower 1/3 = smooth

STOMACH * 4 regions: cardia/body/fundus/pyorus * cardia and body are histologically similar with respect to glands * muscosa thrown into folds (**rugae**) * simple columnar epithelium punctuated by gastric pits * muscularis externa is **3 layers thick** - **additional oblique** fibers for churning gastric mucosa scattered with pale-staining endocrine cells - serotonin, somatostatin, vasoactive intestinal peptide (VIP). these regulate breakdown and delivery to duodenum

GASTRIC GLANDS * tubular @ mucosa * fill lamina propria * 3 main cell types 1. parietal (HCl + intrinsic factor [B12 absorpition]) 2. chief cells (digestive enzymes - pepsinogen, zymogen for pepsin) 3. mucus neck cells (lubricant - acid resistant mucus) * full glands @ body and fundus * no parietal / chief @ cardia and pylorus

STOMACH BODY - GASTRIC MUCOSA * simple columnar epithelium - produce acid resistant mucin * gastric pit invaginations (green arrows) * several tall, straight or brached glands to each pit * submucosa = loose connective tissue with abundant vessels * muscularis externa = 3 layers of smooth muscle muscularis mucosa also contains elastic (black) to stop stomach collapse on empty

PARIETAL (OXYNIC CELLS) * @ gastric glands of body/fundus * @ upper part of gland close to pits * globular - bright pink with H&E * cell surface invaginated (intracellular canaliculi) w/ many mitochondria (dark staining- grainy appearance) * rich in carbonic anhydrase pH - 2

CHIEF (ZYMOGENIC CELLS) * pyramidal @ deeper gland * cytoplasm - blue H&E - contains granules (pepsiogen/lipases) * @ body and fundus * close to muscularis mucosa PEPSIN - affinity for collagen

PYLORIC REGION * cardiac and pyloric glands are shorter * glands are **coiled** * mainly mucus neck cells * scattered with cells producing **gastrin**

GASTRODUODENAL JUNCTION

VILLI AND CRYPTS * intestinal lining - folds - **plicae circularis** (highest @ jejunum, lowest @ distal colon) * further SA increase - villi **villi** - simple columnar epithelium (enterocytes and goblet cells). short life - but replaced by crypt production **contain** - veule, arteriole, lacteal, smooth muscle (milks the villus) **venule and lacteal** to liver **crypts of leiberkuhn** - between villi, stem cell population, migrate to top and shaved off (takes 5 days)

ENTEROCYTES * major absorptive cell * 300 short microvilli on apical surface - **brush border** * @ outer surface brush border = glycocalyx (enzymes) - filter most nutrients through this * water and glucose (some) via intracellular pathways high concentrations of HEXOSE SUGARS mean brush border stains intensely by PAS

DUODENUM * 12 inches, few plicae circularis * villi - broad and leaf like * few goblet cells * **submucsoa** conatins mucus secreting **brunner's glands** - alkaline secretion neutralises CHYME brunner's gland bottom right few pale staining goblet cells long crypts n.b. submucosal brunner's glands not found in jejunum/ileum inner circular layer thicker than outer longitudinal layer of muscularis externa

DUODENUM 2 * crypts form new enterocytes and goblet cells * dividing cells have very dark staining nuclei or sets of chromosomes * @ bottom of crypts = DIFFERENTIATED **PANETH CELLS** * secrete lysozyme - breakdown of bacterial cell walls * regulate flora of gut * bright pink cytoplasmic granules

JEJUNUM * close-packed plicae circularis * **many** goblet cells * long narrow villi (finger-like) * short crypts * loose submucosa (almost detached from muscularis externa) * no brunner's glands or peyer's patches * lymph nodules at lamina propria, but do not penetrate submucosa

ILEUM * final segment of small intestine, therefore fewer plicae and shorter villi (less absorption) * goblet cells increase towards distal end * large **peyer's patches** @ submucosa (lymphoid tissue w/ lymphocytes) * Peyer's patches erupt through muscularis mucosa to lamina propria

ILEUM 2 * serosa (simple squamous) on edge of longitudinal muscle

VERMIFORM APPENDIX * from caecum * simple columnar epithelium * goblet cells * no villi * simple crypts * lamina propria and submucosa full of lymphoid tissue (declines w/ age) * no muscularis mucosa * muscularis externa present * transverse smooth muscle at muscularis externa = **taenia colis** - 3 longitudinal bands * fat filled

APPENDIX 2 * simple columnar epithelium * rudimentary crypts with few goblet cells * lamina propria and submucosa full of lymphoid tissue

COLON * all segment similar histologically * little folding * no villi * mucosa contains close packed crypts with abundant goblet cells and enterocytes * restricted lamina propria (by crypts) * prominent muscularis mucosa * mucosa and sub-mucosa contain a lot of lymph - GALT (gut) * musuclaris externa - thickened inner circular layer, outer layer drawn into 3 longitudinal bands = taeniae coli **this slide - close packed crypts and abundant goblet cells**

RECTO-ANAL JUNCTION * rectum = similar to colon * simple columnar epithelium * anal canal - stratified squamous epithelium, keratinised at distal end (as lip) * submucosa was FAT, VEIN PLEXUS (anal varicosity) * smooth muscle of muscularis externa thickened and surrounded by STRIATED MUSCLE of EXTERNAL ANAL SPHINCTER

RECTO-ANAL JUNCTION * box B - striated muscle of sphincter * box D - anal glands

GI FORMATIVE 5 * villous * sub-mucosa with Brunner's glands * duodenal epithelium contains some lymphocytes between epithelium DUODENUM

GI FORMATIVE 6 * all of this fits on a microscopic slide therefore not colon * flat mucosa with no villi * abundant lymphoid tissue in lamina propria and submucosa * lacks a muscularis mucosa * receives lod from superior mesenteric artery VERMIFORM APPENDIX

GI FORMATIVE 7 * flat surface * no villi * numerous straight crypts * abundant goblet cells * prominent muscularis mucosa * stem cells at base of crypts COLONIC MUCOSA

LIVER * hepatic portal system receives nutrients * main cells - hepatocytes functions: 1. creation/store energy as glycogen & fat 2. synthesise plasma proteins 3. de-amination of amino acids and production of urea 4. uptake, synthesis, excretion of bilirubin and bile acids 5. detox and inactivation of drugs by oxidation, methylation or conjugation * polygonal lobules of cells * each lobule with central vein and radiating hepatocytes (cords) * between cords = sinusoids (blood vessels) - bathe hepatocytes in mix of venous and arterial blood * blood drains from each lobule via central vein - hepatic

LOBULE * cords of hepatocytes * sinusoids (wide, thin, fenestrated capillaries) = 70% portal vein blood, 30% portal artery blood * portal triads at corners of loules * arteriole (hepatic artery), venule (hepatic portal vein - nutrient rich blood), bile ductule * hepatocytes store: **glycogen, trigylcerides** * bile ductule = simple cuboidal epithelium **this slide - small muscular arteriole (top left), venule (bottom), bile ductule (top right, simple cuboidal)** hepatocytes secrete nile to extra-cellular bile canaliculi hepatocytes **replicate**

SINUSOIDS * wide, thin walled, fenestrated capillaries * endothelial cells interspersed with: 1. **kupffer cells** - fixed macrophages 2. **ito cells** - perisinusoidal cells (fat storing) * too thin to resolve * sit of meshwork of reitculin (collagen 3) * separated from heaptocyte cords by **space of Disse** (no blood cells here, but there is plasma) - albumin/fibrinogen synthesised at liver enters blood @ space of Disse **this slide - cords of hepatocytes with paler staining sinusoids between. nuclei of endothelial sinusoidal cells smaller and darker than that of hepatocytes.**

SINUSOIDAL MACROPHAGES * Kupffer cells in lining of endothelium * phagocytose blood borne pathogens * part production of bilirubin (taken up and excreted by hepatocytes) n.b. demonstrate presence by uptake of coloured dye, contain particulate deposits **this slide - Kupffer cells have taken up blue/black ink.** they line cords between pink-staining hepatocytes.

HEPATOCYTE ULTRASTRUCTURE * GI = glycogen * Mi = mitochondria * N = nucleus * RER = rough endoplasmic reticulum sinusoidal membrane contains transport mechanisms for pinocytotic release of macromolecules canalicular membrane is target for bile discharge well devloped rER - synthesis of plasma proteins sER - inactivation of drugs (enzymes) glycogen particule rosesstes and lipid droplets present

GALLBLADDER * BILIARY TREE = ALL CUBOIDAL EPITHELIUM * smaller vessels = simple * distal end = stratified **gallbladder** * simple columnar w/ poor brush border * adapated for water reabsorption (concentrating bile) * epithelium thrown into folds (not villi!) * large veins in walls * smoth muscle at outer surface * serosa visible at top (simple squamous) n.b. contracts by CCK released from duodenum in response to fat from stomach

EXOCRINE PANCREAS * exocrine = 98% of gland * serous (watery/enzyme rich) * digestive enzymes from same cell, secretion granules at upper part of cell * enzymes released as food enters duodenum * enzymes activated by alkaline environment of duodenum stimulated by secretin to release ALKALINE FLUID from CENTRO-ACINAR and small duct cells **this slide - centro-acinar cells by green arrows**

PANCREAS * inset 1. **pacinian corpuscle** - pressure sensor in pancreas (and skin) 2. **nerve plexus** - with vagus nerve also contains **islets of langerhans** (see SUGER)

EXOCRINE PANCREAS DUCTS * each acinus has a narrow intercalated duct (ID) * IDs connect acinus to main duct (MD) * larger ducts -\> 1/2 MDs that enter duodenum with bile duct SIMPLE CUBOIDAL EPITHELIUM (stratified at distal end, as GB) n.b. duct cells produce most of the fluid in secretion

PORTAL TRIAD