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.