ANAT2008:(Principles(of(Histology!
Lecture'1'
Terms!!
•
•
•
•
•
Cell!theory:!all!living!things!are!composed!of!cells!or!the!production!of!cells!
Cytology:!Study!of!cells
The!structure!of!cells!9!Cells!are!organized!into!complex!arrays!of!cells,!called!tissues!
Histology:!Study!of!tissues
Histopathology:!study!of!diseased/abnormal!cells!and!tissues!
Measurement*in*Cytology*
• Most!important!unit!of!measurement!in!cytology:!
o micrometre!–um
o Nanometre!9!nm!
• Most!cells!are!in!the!size!range!of!5920um.!
o RBC!is!7um!in!diameter!
Basic!Tissue!Types!!
•
•
•
•
•
Epithelial!tissue:!characterized!by!very!tightly!packed!cells!
Connective!tissue:!not!tightly!packed!together.!Tendons,!ligament!and!bone!are!all!different!kinds!
of!connective!tissue.!
Nervous!tissue:!consists!of!cells!called!neurons,!these!are!cells!are!specialized!to!conduct!electrical!
impulses.!Neurons!are!quite!tightly!packed!together.
Muscle!tissue:!Cells!are!specialized!for!contraction.!Different!sorts!of!muscle!cells:!smooth,!skeletal!
and!cardiac!muscles!cells.!
Adipose!(fat)!tissue:!consists!of!molecules!called!lipids!which!are!an!energy!store!for!the!body.!Not!
particularly!tightly!packed!together.!In!embryological!terms,!adipose!tissue!is!connective!tissue.!
Sufficiently!structurally!different!that!most!histologists!consider!it!another!type!of!tissue.!
Organs!
•
•
•
•
•
These!are!structural!and!functional!units!
They!have!their!own!nerve!and!their!own!blood!supply!!
Composed!of!different!combinations!of!the!5!basic!tissue!types!!
Almost!always,!the!epithelial!cells!are!the!functionally!most!important!part!–!parenchyma!
(epithelium)!!
Systems!include:!
o Digestive!system:!stomach,!large!intestine,!small!intestine!etc.!!
o Skeletal!system!
Cells!
•
A!cell!can!be!defined!as!the!smallest!thing!that!is!said!to!be!alive
The*Cell*Theory*
• All!living!things!are!composed!of!cells!and!the!products!of!cells!
•
•
Cells!consist!of!one!of!more!nuclei!surrounded!by!a!watery!cytoplasm!which!contains!organelles!
and!is!bound!by!a!plasma!membrane!
All!cells!arise!from!pre9existing!cells!by!cell!division
Eukaryotic*Cells*
• Most!cells!in!the!body!of!mammals!are!eukaryotic!cells.!
• Eukaryotic!cells!have!a!clearly!defined!nucleus!surrounded!by!a!nuclear!membrane!which!withholds!
genetic!material
Prokaryotic*Cells*
• E.g.!bacteria,!don’t!have!a!nucleus,!no!nuclear!membrane!!
• The!genetic!material!is!not!collected!together!in!a!particular!site,!floats!in!the!cytoplasm!!
Plasma!membrane!
•
•
•
Semi9permeable!barrier!around!the!cell.!It!regulates!what!enters!and!exits!the!cell.!
10um!thick,!tramline!appearance!through!the!electron!microscope!
Made!up!of!three!different!classes!of!molecules:!
! Proteins,!lipids,!carbohydrates!9!Fluid!mosaic!model!explains!membrane!
organisation!
! The!lipids!form!a!bilayer!making!up!the!backbone!of!the!membrane.!Heads!facing!
out,!tails!facing!in.!
! Proteins!can!be!integrated!into!the!lipid!bilayer!(integral!proteins)!or!on!the!
periphery!of!the!cell!or!on!the!integral!proteins!(peripheral!protein)!
! Carbohydrates!are!found!exclusively!on!the!outside!of!the!membrane.!
Glycocacyx**
Freeze!fracture!technique!provides!a!direct!visual!confirmation!that!the!fluid!mosaic!model!is!a!good!form!
of!membrane!for!a!cell.!!
Functions*of*Plasma*Membrane*
• Limits!the!cell,!it!separates!one!cell!from!another!!
• Regulates!what!gets!in!and!what!gets!out!!
• Ion!transport.!Transfer!of!charged!particles!across!the!cell!membrane.!!
o Passive!–!moves!along!the!concentration!gradient.!High!–!low!
o Active!–!moves!against!the!concentration!gradient!so!requires!energy.!Low!–!high!
• Receptor!sites!!
• ‘Bulk’!movement!!
o Exocytosis!–!movement!of!large!amounts!of!material!out!of!the!cell!across!the!membrane!
o Endocytosis!–!movement!of!materials!into!the!cell!!
• Cohesion!!
• Communication!
!
!
!
Lecture'2'
Cytoplasm!is!the!substance!inside!the!plasma!membrane!but!outside!of!the!nucleus.!It!can!be!split!into!
organelles!and!cytosol.!
Organelles*in*the*cytoplasm*include:*
Ribosome!
Structure'
• Smallest!organelles!in!the!cell!which!have!fixed!size!and!shape!(25x12nm)!
• Composed!of!equal!proportions!of!protein!and!rRNA!
• Can!occur!free!floating!in!cytoplasm!or!bound!to!membrane!of!rough!ER.!
• Can!occur!singly!(usually!inactive)!or!in!groups!(called!polyribosomes!aka!polysomes)!
Function'
• The!active!unit!in!cells!which!synthesise!proteins.!!
• Polysomes!line!up!along!a!single!molecule!of!mRNA!and!produce!protein!
The*endomembrane*system*is*a*physically*connected*membrane*system*consisting*of*nuclear*envelope,*
golgi*apparatus*and*endoplasmic*reticulum.**
Golgi!Apparatus!!
! Structure'
• Typically!1μm!across!although!enormously!variable!in!size!and!number.!!
• It!consists!of!a!series!of!flattened!curved,!membranous!sacs.!
• Associated!with!the!convex!surface!are!vesicles!(membrane!surrounded!tiny!ball).!!
• Associated!with!concave!surface!is!a!smaller!number!of!much!larger!vesicles!
Function'
• Principle!function!is!to!package!protein!for!secretion.!Proteins!are!packaged!in!rough!ER!to!small!
transport!vesicles!and!travel!to!golgi!apparatus!then!get!modified!then!leave!concave!surface!as!
secretory!vesicles!which!fuse!which!each!other!to!form!much!larger!vesicles!which!fuse!with!plasma!
membrane!where!proteins!are!then!released!from!the!cell.!!
• Involved!in!modification!of!proteins!which!it!packages.!!
o Sulphation!(addition!of!sulphate!groups!to!proteins)!!
o Glycosylation!(addition!of!carbohydrate!groups!to!proteins)!!
• Processing!factory!for!membranes!
!
Endoplasmic!Reticulum!!
! Is!the!most!extensive!of!the!endomembrane!system.!Has!different!shapes!and!different!functions.!!
Structure'
• 2!structural!types:!
o Cisternal9!sheet9like.!Sheets!can!be!long!and!highly!regular!(like!pages!in!a!book)"!regular.!Or!
irregular!(open).!
o Tubular!!
• ROUGH!ER!
o mostly!regular!cisteral!shape.!
o Ribosomes!are!studded!on!surface!of!cisternae!!
• SMOOTH!ER!
o Mostly!tubular!form.!!
Function'
• ROUGH!ER!
o synthesise!protein.!In!particular,!protein!that!is!going!to!be!secreted!from!the!cell!is!synthesised!
on!ribosomes!on!rough!ER.!!
o Rough!ER!also!involved!in!some!aspects!of!lipid!synthesis!
o modification!of!newly!synthesised!proteins!
o also!involved!in!transport!of!newly!synthesized!proteins!around!the!cell.!!
• SMOOTH!ER!
o Synthesise!steroids!(e.g.!oestrogen,!testosterone)!in!the!membranes!of!smooth!ER!
o Involved!in!ion!transport!in!some!cell!types!
o Synthesis!of!glycogen!(energy!store)!
o Involved!in!breakdown!of!carbohydrates!
o Detoxification!of!drugs!(so!lots!found!in!liver)!
Transgolgi'Network'
A!series!of!membranes!associated!with!golgi!app!and!ER.!Involved!in!the!synthesis!of!lysosomes!which!are!
in!turn!involved!in!the!digestion!of!materials!inside!the!cell.!
Lysosomes!
Formed!in!transgolgi!network.!Earl!endosome"!late!endosome"!lysosome.!!
Structure'
• Smooth!(not!coated)!
• Contain!40950!enzymes,!e.g.!acidphosphatase.!These!enzymes!function!at!around!pH!5!
• Stain!a!dark!colour!
Function'
• Carries!out!intracellular!digestion!
• Heterophagy!mean!eating!of!material!different!from!cell.!!
o Involves!phagocytosis!(eating)!and!pinocytosis!(drinking)!
o Enzymes!break!down!these!materials!inside!lysosome!to!the!molecular!level!(proteins!to!
amino!acids,!fats!to!lipids,!etc.)!
• Autophagy!means!self9eating.!Cells!break!down!their!own!unwanted!or!damaged!components.!
These!components!are!surrounded!in!a!membrane!and!a!vesicle!called!an!autophagosome!is!
formed.!The!autophagosome!fuses!with!lysosome!and!again!the!materials!are!broken!down!to!
molecular!level.!!
o Residual!body!(undigested!components)!remain!with!cell!until!it!dies!
Peroxisomes*
Structure'
• Smooth!(not!coated)!
• Contain!catalase!
• Usually!aren’t!darkly!stained!
Function'
• Catalase!breaks!down!hydrogen!peroxide!(H2O2)!which!could!kill!cells!if!it!builds!up!
Coated*Vesicles**
Structure'
• These!vesicle’s!membranes!are!coated!
• Most!of!these!end!up!in!the!lysosomal!system!
Function'
• Involved!in!receptor!mediated!endocytosis9!the!taking!up!of!materials!selectively!from!the!cell!
• E.g.!Familial!Hypercholestermia!(high!cholesterol)!is!a!genetic!defect!for!one!or!more!of!the!
receptors!so!coated!vesicles!can’t!take!up!cholesterol.!!
Mitochondria!
Structure'
• Largest!of!organelles!outside!nucleus.!Largely!differ!in!number!in!size,!~.52μm!
• 2!membranes!
o Outer!mitochondrial!membrane!is!smooth!and!defines!shape!
o Inner!mitochondrial!membrane!is!highly!folded9!folds!called!cristae!!
! Most!are!flat,!shelf9like!structures!
! In!cells!that!produce!steroids,!cristae!are!tubular!!
! In!the!membrane!of!cristae!is!the!electron!transport!chain!
• Matrix!is!the!space!in!the!middle!which!contains!components!of!Krebs!cycle!
Function'
• Produce!energy!as!ATP.!The!more!cristae!it!has,!the!more!ATP!is!produced!
• Sometimes!involved!in!concentration!of!ions!(e.g.!calcium)!
• Sometimes!involved!in!aspects!of!fatty!acid!metabolism!
Nucleus!
Round!or!elongate!structure!close!to!centre!of!the!cell.!4!components:!
Nuclear*Envelope*
Structure'
• Double!membrane!which!runs!parallel!with!each!other!
• The!two!membrane!sometimes!form!nuclear!pores!(~70nm!diameter)!
o Not!simply!a!hole9!contains!elaborate!structure!called!nuclear!pore!complex!
• Space!between!the!two!membranes!is!called!the!perinuclear!space!(~10915nm)!
• In!many!cells!it’s!continuous!with!rough!ER!and!has!ribosomes!on!it!
Function'
• mRNA!leaves!nucleus!via!nuclear!pores!
• nuclear!pores!are!actively!engaged!in!regulating!passage!of!materials!in!and!out!of!cell!
• nuclear!envelope!is!the!second!permeability!barrier!in!the!cell9!separates!the!genetic!material!from!
the!cytoplasm!of!the!cell!
Nucleoplasm*
• featureless9!roughly!30%!dry!weight!protein!
• no!membranes!
• powerful!influence!on!how!genetic!material!functions!
Nucleolus*(plural*nucleoli)**
Structure'
• dense,!darkly!stained,!generally!rounded!structure.!Sometimes!see!arrangements!of!light!and!dark!
components!
• active!cells!have!more!nucleoli!
Function'
• involved!in!synthesis!of!rRNA!
• factory!for!synthesis!and!assembly!of!rRNA!to!make!ribosomes!
Chromatin*
Structure'
• DNA!complexed!with!various!proteins!
• 2!kinds:!
o heterochromatin9!darkly!staining.!This!is!inactive!DNA.!Most!of!it!is!in!the!tightly!packaged!
form,!can’t!synthesise!DNA!as!it!is!so!dense!and!thus!stains!darkly.!
o Euchromatin9!pale!staining.!This!is!active!DNA.!
• A!cell!with!a!small!dark!nucleus!is!pretty!inactive!
• Organized!into!units!called!nucleosomes!(~10nm!diameter).!DNA!is!wound!around!a!protein!core.!
To!fit!DNA!into!nucleus!it!must!be!packed,!as!it!is!too!long.!DNA!is!packed!about!10!times!more!
tightly!than!it!would!be!if!it!were!completely!unraveled.!In!chromosomes,!DNA!is!10000!times!more!
tightly!packed!than!if!it!was!completely!unraveled!
Function'
• Genetic!material!!
Cytosol!
This!is!the!watery!component!of!cytoplasm.!Relatively!featureless!however!is!highly!organized!containing!a!
network!array!of!cytoskeleton.!There!are!3!different!components!of!the!cytoskeleton:!
Microtubules*
Made!of!protein!called!tubulin!(60000mw).!These!are!the!largest!components!(24nm!diameter).!The!
protein!forms!long!tubes!end!on!end.!Numbers!and!lengths!of!these!tubulin!molecules!are!highly!variable.!
Microfilaments*
There!are!2!kinds!of!microfilaments!found!in!all!eukaryotic!cells!(more!densely!packed!in!muscle!cells).!
These!can!both!contract!(are!contractile):!
!!!!!!9!Actin!6nm!
!!!!!!9!Myosin!15nm!
Intermediate*Filaments*
7910nm!diameter.!All!eukaryotic!cells!have!them!but!they!differ!in!different!types!of!cells.!This!can!be!useful!
in!diagnosis!as!you!can!identify!the!type!of!cell.!These!intermediate!filaments!are!associated!with!
maintaining!structure.!
Cytoskeleton*Functions*
• As!a!whole,!the!cytoskeleton!maintains!cell!shape!(especially!microtubules).!!
• Involved!in!exocytosis!and!endocytosis!(moving!materials!into!and!out!of!cells).!!
• Involved!in!transport!of!materials!inside!the!cell.!!
• Involved!in!movement!of!cells!(e.g.!WBC!move!around!tissues!destroying!bacteria!etc).!!
• Involved!in!sensory!receptors!particularly!in!some!cells!(e.g.!ear!hairs).!!
Centriole*
A!very!important!component!of!cytoskeleton.!All!animals!have!a!pair!of!these.!!
Structure'
They!are!usually!.5x.2!microm!in!size!and!lie!at!right!angles!to!each!other.!The!wall!of!centriole!is!made!up!
of!9!groups!of!3!microtubules.!!
Function'
The!centriole!and!its!surrounding!material!(pericentriolar!material)!are!critical!for!cells!functions!such!as:!
o Critical!in!the!mechanisms!in!cell!division!
o Important!in!formation!of!structure!called!basal!body!which!is!involved!in!formation!of!cilia!
o Master!organizer!of!cell!shape!
'Lecture'4'&'5:'Epithelial'Tissue'
•
•
•
•
The!boundaries!of!our!bodies!are!formed!by!continuous!sheets!of!cells9!separating!us!from!the!
outside!environment!
Separate!a!constant,!fairly!controlled!internal!environment!inside!body!from!an!often!hostile!
outside!environment.!!
E.g.!skin,!gut,!lung.!!
Gut!is!cavity!which!extends!from!mouth!through!stomach!to!anus.!The!space!inside!is!called!lumen;!
it’s!deep!inside!body!but!is!continuous!with!outside!world.!!
The!following!don’t'separate!internal!environment!from!external!environment:!
•
•
Endothelium9!tissues!that!line!blood!vessels!
Mesothelium9!tissues!that!line!internal!closed!cavity!
Commonalities!between!all!Epithelial!Cells!
1. Cellularity*
Epithelial!tissues!consist!only!of!epithelial!cells!which!are!tightly!packed!together!
2.*Polarity*
They!are!polarized.!The!top!end!(apical)!faces!outside!world!and!the!bottom!end!(basal)!faces!inside.!The!
lateral!surfaces!are!the!sides!which!face!each!other.!The!polarity!is!expressed!in!different!sorts!of!structures!
in!different!regions!of!the!plasma!membrane!inside!epithelial!cells.!!
Stratified!
Squamous!
•
•
•
•
•
Stratified!Cuboidal!
and!Columnar!
•
•
•
Typically!specialized!for!protection.!
They!are!in!places!subject!to!abrasion!
(e.g.!skin)!
They!have!a!rapid!cycle!of!cell!division!
and!migration.!Cells!divide!at!the!
base,!migrate!through!pile!up!to!
surface!and!change!shape!at!the!top.!
Then!cell!death!occurs!at!the!top.!!
Numerous!desmosomes!are!in!the!PM!
to!hold!each!cell!to!adjacent!cells.!!
Basal!epithelium!have!numerous!
hemidesmosomes!!
Keratinization9!keratin!is!a!protein!
manufactured!by!epithelial!cells.!It!is!
highly!water!insoluble!and!a!
mechanically!strong!protein!(due!to!
disulfide!bridges).!Cells!synthesise!
keratin!at!the!base,!then!more!and!
more!keratin!is!produced!as!you!move!
toward!apical!layer.!The!cells!at!the!
top!die!and!keratin!proteins!fuse!
together:!‘squames’.!!
Not!very!common!in!bodies!of!humans!
and!animals!
Usually!only!2!or!3!cells!thick!
Often!found!where!other!epithelial!
sorts!join!
‘false’9!looks!stratified!but!is!not.!!
All!cells!are!in!contact!with!basal!lamina!
but!not!all!cells!are!the!same!height!
Pseudostratified!
•
•
Transitional!
Epithelium!(a!type!
of!stratified!
epithelium)!
• Only!found!as!lining!of!bladder!and!of!
upper!urinary!tract!
• Called!transitional!because!it!changes.!
As!bladder!fills!up!with!urine,!
epithelium!stretches!to!cover!a!larger!
surface!area!
• Very!large!apical!cells!(many!of!which!
are!binucleate9!2!nuclei).!In!an!empty!
bladder,!these!cells!are!somewhat!
cuboidal!but!become!thinner!as!it!fills!
with!urine!
• Apical!surface!is!refractile!border!which!
•
•
•
•
cells!have!a!prominent!brush!
border!made!up!of!microvilli!to!
dramatically!increase!surface!
area!across!which!absorption!can!
take!place.!They!have!a!well9
developed!lysosomal!system!to!
digest!material!absorbed.!They!
also!have!tight!tight!junctions!to!
ensure!2!separate!environments.!!
Namely!protection!
Desmosomes!and!
hemidesmosomes!hold!the!cells!
in!place!
Keratin!makes!you!waterproof!
Some!sites!where!this!epithelium!
is!kept!moist!e.g.!in!human!
oesophagus!and!lining!of!vagina.!
In!these!sites!keratin!doesn’t!
form!
• Seem!to!have!a!predisposition!to!
forming!cancers!
• Lining!of!trachea!with!prominent!
basement!membrane!and!
prominent!goblet!cells.!Get!to!
know!well!will!most!defs!be!in!
exam!
• Refractile!border!protects!apical!
cells!from!osmotic!shock!as!cells!
could!lose!water!to!urine!via!
osmosis.!Urea!is!toxic!so!refractile!
border!also!protects!cells!from!
toxic!shock!
• Tight!tight!junction!ensure!no!
leakage!of!toxic!urine!
!
Mesoderm!
•
Gives!rise!to:!
o Connective!tissue!
o Striated!and!smooth!muscles!
o Heart,!blood!vessels!and!lymphatic!vesses!
o Spleen!
o Kidneys!and!gonads!
o Mesothelium!
o Adrenal!cortex!
Endoderm!
•
Gives!rise!to:!
o Digestive!tube!
o Epithelium!of!bladder!and!urethra!!
o Respiratory!system!epithelium!
o Thyroid,!pancreatic,!lung!cells!
Germ!Cells!
•
•
Sperm!!
Egg!
Lecture'21:'Cell'and'Tissue'Interactions'
•
•
•
Started!off!with!a!zygote!that!has!materal!and!pateral!DNA!
Gastrulation!results!in!3!germ!layers!(ectoderm,!mesoderm,!endoderm)!
How!does!one!cell!give!rise!to!the!many!cells!of!the!adult!body?!=!cell!differentiation!
Cell!differentiation!
•
•
•
Involves!the!structural!and!functional!specialisation!of!individual!cells!
Cells!of!a!common!lineage!(e.g.!ectoderm)!which!normally!develop!in!several!different!ways!
(pluripotent)!begin!this!differentiation!by!activating!specific!genes!
Cell!activates!genes!which!make!cell9type!specific!proteins!which!commits!the!cell!to!a!specific!
differentiation!pathway!
o E.g.!erythrocyte!"!haemoglobin!"!transport!oxygen!
What*specifies*the*differentiation*of*a*cell?*
• The!fate!of!a!cell!depends!on!its!interaction!with!other!components!of!its!immediate!environment!
• Cells!can!be!influenced!by!neighbouring!cells!or!tissues!and/or!by!morphogens!(soluble!molecules)!
secreted!by!these!tissues!!
o Inducing!cell!
o Differentiating!cell!
• Can!influence!each!other!by!cell9to9cell!contact!(soluble!molecules!that!get!secreted!by!cell)!
o E.g.!cell!x!switches!on!gene!which!expresses!protein!(soluble!factor),!cell!y!is!switching!on!
genes!for!specific!receptor.!Cell!y!will!respond!based!on!what!cell!x!is!produces.!When!cell!x!
!
Other*dyes*
• E.g.!Sudan!dye9!fat!soluble;!can!label!lipids!in!frozen!sections)!
Immunolabelling!
•
•
•
•
Used!to!detect!specific!proteins!in!cells!and!tissues!!
o Using!a!specific!antibody!for!the!protein!of!interest!
Specific!antibodies!can!be!raised!in!different!animals!(e.g.!rabbits,!sheep!or!mice)!
Some!antibodies!are!tagged!so!that!they!can!be!visualized!under!a!microscope!
Antibodies!can!be!tagged!with!either:!
o A!specific!enzyme!that!will!react!with!a!specific!substrate!to!give!a!colour!reaction!=!
immunohistochemistry!!
o A!fluorescent!tag!=!immunofluorescence!
o A!colloidal!gold!particle,!a!uniform!particle!of!known!size!=!for!EM!analysis!
Direct*Labeling*
• Primary!antibody!is!tagged!and!attaches!to!antigen!directly!
Indirect*Labeling*
• Secondary!antigen!is!tagged!and!binds!to!primary!antibody!which!has!bound!to!antigen!!
Visualisation*
• Bright9field!microscopy!
o Enzyme!colour!reaction!products!
o Used!for!thin!sections!and!thin!whole!tissues!
• Fluorescence!Microscopy!
o Used!for!thin!sections!and!tissues!
o Detects!molecules!(antibodies)!that!fluoresce!
In!Situ!Hybridisation!
•
•
•
!
!
!
Antibodies!are!quite!expensive!so!this!may!be!used!as!a!cheaper!alternative!
It!is!the!binding!of!a!labeled!nucleic!acid!(RNA)!probe!to!specific!mRNA!in!histological!tissues!
Stable!RNA!hybrids!can!be!detected!and!visualized!using:!
o Bright9field!microscopy!(using!immunohistochemistry)!