Histology - created from Mind Map

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If you see a lesion...

fixation

epithelial cells

mesenchymal (connective tissue)

1. make a diagnosis

2. Determine a prognosis - is it malignant/aggressive?

3. Plan treatment

4. Predict/confirm response to drugs

Asymmetry | Border | Colour | Diameter | Evolving

biopsy - what needs to be done?

excision - is it comepletley out?

related to prognosis: is additional/aggressive treatment needed?

will a post-operative (adjuvant) treatment be beneficial?

did a pre-operative (neoadjuvant) treatment show an effect?

preserves the tissue by...

fixatives

tissue processing: dehydration via ethanol, replace alcohol with xylene (clearing), replace xylene with wax (wax infiltration), formalin fixed

Periodic Acid Schiff (PAS): detection of mucin --> fungal organisms and visualisation of basement membranes. Problem = glycogen is PAS positive

detection of mucin --> fungal organisms and visualisation of basement membranes. Problem = glycogen is PAS positive

combined with diastase (DPAS) - enzyme diastase removes glycogen

stopping intrinsic autolytic enzyme action

prevents putrefication/decay

increases mechanical strength to preserve morphology

aldehyde

alcohol

oxidative - forms protein cross-links

freezing (quick but poor morphology)

e.g. formalin (formaldehyde solution) | forms protein cross-links, good mechanical strength and penetration | poor nucleic acid preservation

e.g. glutaraldehyde (like formalin but larger) | needs smaller tissue samples | works well at low temperatures | used for electron microscopy

e.g. ethanol | reduces protein solubility --> percipitation | nucleic acid research (doesn't cross link) | used in cytology smears

main features

classification

specialisation

epithelium

endothelium

disorders of epithelial function

line all body surfaces except articular cartillage, tooth enamel and anterior iris

cellular

sits on basal lamina

stuck tightly together by intracellular junctions

polarity - apical or basal

avascular

rapid turn-over

number of cells

shape of cells

1 layer = simple

multi-layered = stratified

psuedo-stratified - single layer of columnar cells e.g. upper airways - cillia and goblet cells

transitional - multiple layers but changes shape (squamous and flat), bladder and urinary tract

squamous (flat)

cuboidal

columnar

cillia - push mucus along

secretory - release stuff

microvilli increase SA of epithelium

for protection

for absorption

for surface movement

for gas exchange

prevents dehydration, chemical, mechanical etc. damage

covering of inter/outer surfaces

stratified

replicative to replace sloughed (shed) cells

tight seals between cells

keratinisation

locations

squamous: oesophagus, skin, vagina

transitional: bladder, urinary tract

epithelial lining of gut specialised for absorption e.g. glucose, ions, water

relies on cell polarity

adaptations such as brush border

cilia move in co-ordination to provide unidirectional movement

locations

airways - mucus

testes - sperm

fallopian tubes - ova

simple squamous cells that line blood vessels - minimal distance for diffusion

for surface lubrication

for sensation

for secretion

mesothelium is simple epitheloium e.g. serosa (which secrete a lubricating fluid which reduces friction from muscle movement)

lines all body cavities

potential spaces contain protein rich fluid (serous)

sensory organs are highly specialised epithelia

ectoderm - nervouse system - all senses

isolated epithelial cells e.g. goblet cells

organised multicellular glandular structures

secretory glands

endocrine glands - product released into blood

exocrine glands - product is released onto surface

classification

mechanisms of exocrine secretion

mercorine

apocrine

holocrine

fused plama membrane recycled by endocytosis

e.g. breast milk casein

apical membrane is pinched off (loss of membrane)

e.g. breast milk lipids

cell disintegrates to release product (cell suicide)

e.g. sebum in sebaceous glands

epidermolysis bullosa

congenital cilliary dyskinesia / Kartagener's syndrome

cystic fibrosis

blistering skin disorder

inherited gene mutation of adhesion molecules that stick epithelium to basement membrane - abnormal anchoring of epidermis to dermis

autosomal recessive

abnormal cilliary function - secretion accumulation

brinchiectasis | sinusitis | situs inversus

mutation in CFTR gene

defective Cl channel on apical surface of epithelila cells - less water in mucus - thickens and builds up