Histology Flashcards
done to 24
4 tissue types
epithelial, connective, muscle, nervous
define histology
study microscopic structure of tissue
branch of anatomy
essential for understanding function, abnormalities + pathological change
avg cell mem thickness
7.5nm
nucleus + nucleolus diameter
4µm 1µm
length mitochondrion + width cilium
0.5 - 4µm 250nm
resolution LM + EM
w/in 0.2µm 0.5nm
plasmalemma
pm bounding cell, esp directly inside plant cell wall
steps tissue processing
- fixation
- embedding
- sectioning
- mounting
- de-waxing
- staining
describe fixation process
- dehydration by dipping incresing conc alcohol sols up to 100% to replace water in cells w alcohol
- clearing w organic solvent, e.g. xylene, - dissolve alcohol (+ lipids :()
bc wax + water not miscible
why fixation
prevent rotting - bac/fungal attack; autodigestion by enzs leaking out lysosomes
how fixation works
binding sites form cross-links bet 2 prots so stay in place (or 2 locations on prot for shape)
spare sites bind (+ deactivate) microbes - prevents digestion
embedding process
poor on wax (LM) / resin (EM) to provide scaffolding for support in sectioning
problems w tissue processing
- heating + dehydration can damage/alter tissue structure, e.g. shrinkage/tearing
- hardening tissue by freezing but icicles, then melt = holes
sectioning process
using sharp microtome, wanting 1 cell thick (5-7µm), LM or 1 organelle (100nm), EM - best if makes continuous ribbon
process mounting
slide slide under ribbon floating in water
de-waxing process
reverse fixation
* xylene dissolves wax
* 100% alcohol to remove xylene
* decreasing alcohol conc sols to water
why de-waxing
- not natural part tissue so needs removal before viewing
- most conventional stains waterbased so need for stain penetrate
routine LM stain
Haemotoxylin + Eosin (H+E)
every prot in cyt -> pink so cyt pink
why staining necessary
cells pretty much colourless
why nucleus visible
histone prots fixed in place + NAs coiled around (forming chromatin)
histochemical stains
specific - used highlight certain parts cell, e.g. enzs or chemical components
trichrome
how stains work EM
stained w heavy metals
* heterochromatin has affinity bc area e- density = takes it up = dark + e- beams deflected off
* euchromatin e- lucent = e- beams pass through
* vesicles e- dense
common EM stain
Osmium tetroxide (OsO4) - stain + fixative
stabilises lipids so e- dense + black = visible = specialised stain
description + purpose myelin sheath
concentric layers myelin (lipid) around axon to:
1. protect
2. insulate
3. make more efficient at conducting
When to change light intensity on LM
increased mag = smallr specimen field = more light required
and vice versa
= turn up lamp + widen diaphragm
epithelial tissues
form barrier bet other body tissues + internal/external environ across which all exchanges take place, defending underlying tissues
features common to all epithelia
- cellular = no connective tissue fibres holding cells together
- avascular = no blood vessels
- self-regen from stem cells lying w/in epithelium
- sepped underlying tissues by basal lamina
- supported underlying layer connective tissue cont bvs (metabolic support)
2 types epithelia
- simple = single layer cells
- stratified = multiple cell layers
purpose basal lamina in epithelia
attachment structure to allow attachment ep cells to connective tissue
how epithelial cells held together
cell junctions
1. occluding = tight + selectively permeable, act as barrier
2. anchoring for strength
3. communicating for movement bet cells = gap junction
basolateral surface
surface that adjoins underlying tiss
type anchoring cell junctions
desmosomes for cell-cell attachment
hemidesmosomes attach cell to basement mem
multiprot complexes to facilitate adhesion
where simple epithelia found + why
found only internal protected surfaces bc too delicate constitute defensive barrier against mechanical damage (as single layer)
types simple epithelia
- squamous
- cuboidal
- columnar
- pseudostratified
types stratified epithelia
- squamous
* squamous
* keratinised
* parakeratotic - transitional
structure + function simple squamous epithelium
- nucleus flattened + cytoplasm indistinct (0.1μm < res LM + not visible)
- slick surface for flow fluids
- insufficient cyt for organelles involved secretion
- rapid transport due short diff dist, e.g. lungs)
- large SA
- low friction = cover internal organs as move against each other, e.g. lining pleural cavity
endothelium
epithelium internal lining blood vessels - simple squamous
structure + function simple cuboidal epithelium
- cube-shaped cells w central, round nucleus
- not involved synthesis except form walls thyroid follicles + involved formation thyroid hormone
- often lining secretory part exocrine glands; duct walls
structure + function simple columnar epithelium
- rectangle w oval nuclei
- nuclei lying same level towards base cells
- more cyt than squamous/cuboidal = engage more cellular activity
- specialised absorption + secretion, e.g. lining intestine - diff functions = diff morphology
how simple columnar epithelium specialised secretion
no apical specialisations but goblet cells can sweel w mucus (lubricant)
how simple columnar epithelium specialised absorption
microvilli (finger-like protrusions) surface increase SA for increased Roabsorption
visible as finger-like protrusions under EM, like brush border under LM
how simple columnar epithelium specialised move mats over epithelial surface
cilia, e.g. airways
structure + function pseudostratified columnar epithelium
- single layer cells all in contact w basal lamina but not all reaching free surface
- nuclei at diff levels in lower half of cells
- resulting from apical specialisations bc all cells slightly diff
- e.g. ciliated + goblet together in airways
structure + function stratified squamous epithelium
- basal layers cuboidal, upper layers squamous
- defence against mech damage as can withstand shearing forces coarse food, e.g. oral cavity, oesophagus
- desmosomes for integrity
- rete pegs for attachment
how are stratified epithelia classified (named)
superficial layer gives rise to naming
rete pegs
peg-like downgrowths from lowest layer cells into underlying connective tissue to attach
structure + function keratinised stratified squamous epithelium
- constant renewal as dealing w damage like microtears from eating
- as cells move up through layers become squamous + accumulate granules keratohyalin (stains dark blue H+E)
- abruptly adjacent layer more superficial no cellular detail + keratohyalin replaced red-staining keratin
- rete pegs to anchor
cornification
formation layer dead cells w/o cellular detail filled w keratin
keratin
- physically strong, chemically inert, semi-waterproof
- forms epidermis + protects mech damage, chem damage, dessication
- allows retain shape
epidermis
epithelial layer of skin
structure + function parakeratotic stratified squamous epithelium
- stratified squamous but superficial cell layer has cellular detail + keratinisation
- allows absortion products fermentation, e.g. shortchain fatty acids
- ruminant forestomach only in GI tract
structure + function transitional epithelium
- some cells so big 2 nuclei
- as cells move up from base get fatter + rounder
- no keratin or rete pegs (not subjected shearing forces etc)
- urinary sys only as stretch when bladder fills - can accomodate variable vol fluid w/o rupturing
- stretch laterally w balloon shape
oblique section demonstrated
single secretory cells found?
scattered in simple epithelia = individual exo/endocrine cells, e.g. goblet cells
gland defn
grp cells main function synth + secretion mat w extracellular function, excl neurotransmission
* e.g. prots (enzs, hormones), mucous, steroids, lipids)
aggregates secretory cells into downgrowths epithelium
embryological origin endocrine glands
- derived mesodermal layer + don’t retain connection w epithelium, e.g. thyroid
- neuronal
* neuronal w morphology retained, e.g. hypothalamic neurons release hormones into blood from axon terminals
* endocrine = adrenal medulla, releasing NTs into blood w phenotype altered
classification glands based on function
- apical secretion = into free epithelial surface = exocrine w connection epithelial via drainage duct
- basal secretion = into underlying connective tissue = endocrine w/o connection epithelium
exocrine vs endocrine glands
- exocrine ducts, endo ductless
- exocrine prots etc, endo hormones
- apical vs basal secretion
- exo secrete through duct sys directly to site where used, endo secrete into blood to be carried to target organs
classification exocrine glands based shape
- simple
- compound
simple exocrine gland structure + function
- single duct, unbranched
- secretory units tubular or alveolar (= acinar)
- secretory unit drains directly onto epithelial surface
- rare as punctures protective epithelial layer lots = poor design
examples simple exocrine glands
- sebaceous w no duct, secretory unit opens directly into hair follicle - acinar
- sweat - each secretory unit own duct to drain onto epidermis - coiled
compound exocrine gland structure + function
multiple ducts from many secretory units join form large single duct, opens epithelial surface
* epithelial barrier only weakened 1 pt
* allows put secretory units somewhere convenient, e.g. parotid salivary ventral outer ear, ducts through cheek wall
* tubular, alveolar, or tubuloacinar (mix)
classification exocrine glands based secretion type
- serous - alveolar units
- mucous - tubular units
- seromucous (mix)
serous glands structure + function
- most prots secreted enzs
- some other purposes, e.g. nutritive prots from mammary gland (also lipids)
- alveolar = pyramid shaped cells - strong-staining as intracellular storage lots secretory prots
mucous gland structure + function
- secretes proteoglycans (mucous) = lubricant
- tubular units made columnar epithelial cells - pale-staining due large intracellular mucous store
- mucous store = cell swollen = nucleus flattened towards base
mixed seromucous gland
gland w tubular + alveolar units OR serous demilunes = mucous units capped crescent-shaped serous cells (along edges)
e.g. mandibular salivary gland
classification exocrine glands based mode of release
- merocrine
- apocrine
- holocrine
merocrine gland descr
vesicle releases secretory products into duct via exocyt
apocrine gland descr
mem-bound vesicle pinched off (w some cytoplasm) + deposited on epithelial surface
holocrine gland descr
entire cell sheds into duct then dying cell pm ruptures, releases secretory products
* formation replacement cells
endocrine gland structure
each gland own morphology
sometimes cells aggregated around caps, e.g. islets Langerhans in pancreas prod insulin + glucagon
thyroid gland structure
prods T3 (triiodothyronine) + T4 (thyroxine) to regulate basic metabolic rate
* lipophilic hormones so formed + diff out into target cells enseguida
cells organised follicles (= hollow balls cuboidal epith)
how does thyroid gland ensure healthy animal never runs out T3/T4
- heavily iodinated precursor prot thyroglobulin (TGB) synthed + secreted (exocrine) apical cells for storage in follicle
- thyroid hormones needed = cuboidal epith cells take up TGB + breakdown by phagocytosis, releasing active T3/T4 to diff out into cap beds for distrib in body = endocrine
central cavity follicles filled sticky colloid fluid (hormones synthed)
adrenal gland structure
2 main parts w diff functions
1. adrenal medulla
2. adrenal cortex
adrenal medulla structure + function
centre gland derived sympathetic neurons (but lost neuronal phenotype) = neuroendocrine
* neurohormones (mostly adrenaline, tiny noradrenaline (catecholamines)) secreted blood
* cells under nervous control from symp ns
* granular cyt w many vesicles
adrenal cortex structure + function
gland conts cells for synth + release hormones w 3 areas
1. zona glomerulosa
2. zona fasciculata
3. zona reticulata
zona glomerulosa
- secretes mineralocorticoids - aldosterone
- signals from kidneys - reabsorb Na+ for water + electrolyte balance
zona fasciculata
- secretes glucocorticoids, e.g. cortisol, increasing in response to stress
- signals from hypothalamus + pituitary
- pale-staining as prod steroids from lipid
zona reticulata
- secretes sex steroids (androgens, sex hormones)
- signals from hypothalamus + pituitary
myogenesis
process all muscle cell types from in embryogenesis
myocyte
= mucle cell = muscle fibre = myofibre
* characteristically long + fibre-like, arranged parallel direction contraction
basic structure sk musc
muscle cells surrounded CT (endomysium), aggregated form fascicle surrounded CT (perimysium), aggregated form muscle surrounded CT (epimysium)
at end CT condenses allow connection to bone (e.g. tendon)
CT for insulation
general features sk myocytes
- synctium = cells fused so long + multinucleate
- nuclei at periphery
- parallel unbranching fibres
- striated
- 10-110μm diameter, 30-50cm length
- cell mem = sarcolemma + modified SER = sarcoplasmic reticulum (SR) + cyt = sarcoplasm
motor unit
motor neuron + select muscle fibres it transmits to
* contraction each fibre all-or-nothing but graded response depending no. recruited fibres
* allow selective contraction to control strength + extent contraction
what causes striations sk musc
dark-stained A(nisotropic) bands + light I(sotropic) bands
* A have thick myosin (+ actin) = heavily proteinated = no light through, but I only actin
sarcomere
= contractile unit
dist bet 2 z-discs/z-lines @ centre I band
myofibrils
parallel arrangements thread-like elongated structures running whole length sarcoplasm myocyte
* have 2 myofilament types
1. thick myosin
2. thin actin
structure myosin filament in sk musc
made myosin prots, each w 2 globular heads + tail
* heads have binding sites actin + ATP + some ATPase activity
structure actin filaments
globular actin prots end-to-end
* form longitudinal strands that twist round each other
* in groove bet 2 strands = prots tropomyosin + troponin
contraction sk
- influx Ca2+ from SR binds troponin on actin myofilament
- conformational change troponin = tropomyosin unbinds actin
- myosin binding sites exposed = actin-myosin interaction
- E released at same time + myosin head pulls attached actin towards centre sarcomere
- sarcomere shortened + muscle cell contracted
- myosin head binds new ATP, detaches actin, lengthens, repeat
muscle spindle
stretch-responsive sensory receptor - receives input to stretch + immediately contracts + sends feedback CNS
modified muscle fibre
transverse tubules (t-tubules)
invaginations of sarcolemma to carry depolarisation (a pot) from motor nerve into myocyte rapidly to effect on terminal cisternae
* sac-like regions on SR for Ca2+ storage
ensure simultaneous contraction myofibrils in each cardiac muscle cell
structure cardiac myocytes
- joined at ends by intercalated discs
- not syncytium
- cells may branch
- central nuclei
- striated
- more + larger mitochondria due more aerobic resp
how can cardiac muscle maintain contractions over long time
t tubs more developed + release more Ca2+
intercalated discs
transmit contraction force bet cells
* low elec resistance so muscle impulse cell-cell fast
* acts like functional syncytium so cells contract all together
bet cardiac muscle cells
Purkinje fibres
specialised myocytes to conduct a pots more quickly + efficiently
* allow synchronised, spontaneous contraction = consistent heart rhythm
* lots glycogen
pale staining w H&E as fewer myofibrils
smooth muscle cell structure
- tapered ends = nucleus often not visible TS
- visceral = no striations
- unbranched
- no t-tubules
- gap junctions bet cells - communicate, coordinate, less precision
- v little SR
- elongated nuclei
regeneration smooth myocytes
pericytes = undiffed cells
1. hyperplasia (increase cell nos)
2. hypertrophy (increase cell size)
criteria to be lymphoid organ
need partial or complete connective tissue capsule surrounding organ
otherwise accessory lymphoid tissue
primary vs secondary lymphoid organs
- where lymphocytes receive immunocompetence (bone marrow (B) + thymus (T)) = site maturation
- receive lymphocytes, e.g. lymph nodes, spleen, tonsils
non-specific, innate immune defences
- skin + mucous mems - protective surfaces/secretions
- internal defences - inflammation, phagocytosis
specific is acquired or adaptive
basic lymphocyte development
precursor B + T cells derived stem cells, mature + stimmed by foreign invaders
* diff into cells that effect immune response (effector cells) or remember antigen for quicker response next time (memory cells)
secondary lymphoid tissue
- tonsils
- Peyer’s patches = gut associated lymphoid tissue (GALT)
- mucosal associated lymphoid tissue (MALT)
- broncheal associated lymphoid tissue
….
thymus, LP under LM
- v purple = lymphoid organ
- lymphocytes small round purple cells w v little cyt
- lobules w CT sepping them w/in organ
Hassall’s corpuscles
in medulla THYMUS ONLY - epithelial cells concentrically surrounding cell debris
look like roses
lymph nodes
role + paradox
- filter lymph fluid through cortex + medulla + return to blood = physical barrier
- immunosurveillance w lymphocytes + phagocytes
- barriers to spread infection + tumours by containing + destroying antigens/microbes
- also facilitate spread through lymphatic circulation
clinical importance lymph nodes
enlarge when activated by infection so swelling indicates disease
germinal centres lymph node
at centre nodules (follicles) in cortex - where B + T cells proliferated + activated
trabecula
CT going into lymph node (+ others, not thymus) from external capsule for structural support
why is stained medulla paler than cortex in lymph node
lymphocytes v little cyt = mostly nucleus = v purple
epithelial cells more cyt = paler
medulla has higher prop epithelial cells than cortex
spleen function
filter blood - involved immunosurveillance in left abdomen
spleen basic structure
- red pulp - mostly rbcs
- white pulp - wbcs (B, T, macrophages) (purple in stain)
tonsil structure
- no capsule
- lined oral epithelium
- follicles w B-cell germinal centres when stimmed antigens (all the time)
cellular els of blood + purposes
- erythrocytes for gas exchange to transport O2 + CO2 bet lungs + peripheral tissues
- leukocytes for defence against infectious + injurious agents
- platelets/thrombocytes to stop bleeding (= haemostasis
plasma
sol of blood in which cells dispersed made water + plasma prots
plasma prots + purpose
- albumin
- globulins = immunoglobulins, fibrinogen, clotting factors + complement
provide oncotic press = osmotic press exerted by prots in sol, preventing movement water from 1 sol into other
* water no move plasma across semipermeable mem (vascular endothelium) into interstitial fluid or vice versa
functions plasma
- transport nutrients, hormones, waste products, heat
- homeostasis - maintain blood fluidity, pH, water content
serum
plasma but w/o clotting factors (inc fibrinogen)
where are cell components blood proded
rbcs, wbcs + platelets
haematopoietic tissues
* haematopoietic islands in yolk sac embryo
* bone marrow - major
* extra marrow sites - liver, spleen, kidney (fish + amphibians)
haematopoietic cells
multipotent, primitive + can develop any type blood cell
types bone marrow
- red marrow = mostly haematopoietic cells, mostly in long, flat bones - spine, hips, sternum
- yellow marrow = mostly fat cells, can be converted haematopoietic lines
maturation erythrocytes
lose organelles inc nucleus -> anucleate, biconcave discs = erythropoiesis
* in bone marrow, final stage whilst circulating in blood
anucleate = no nucleus
stain pink due Hb
general variations in rbc size + shape bet species
w photos
- cat + equine = Rouleaux formations = dysproteinaemia = coin stacks
- camelids = elongated
- central pale area more obvious dogs, goats; less in cats, horses
- non-mammalian = nucleus, ellipsoid, large
variation colour rbc
beyond normal small amount
polychromasia
variation in rbc size
beyond small normal amount
anisocytosis
variation in shape rbc
beyond normal small amount
poikilocytosis
prominent central pallor rbc
hypochromia = hypochromasia, possibly indicating reduced Hb conc
role carbonic anhydrase in gas exchange
facilitates transport O2 + CO2
how can rbc carry O2
adult Hb has 2α + 2β chains, each w Fe-cont haem grp that can bind 1O2 mol
how is structure foetal Hb diff from adult + why
2γ chains instead of β, giving higher affinity O2, enabling placental O2 transfer
what happens as erythrocytes age
- more rigid, less deformable = more prone damage whilst circulating
- changes in p mem, recognised by macrophages so removed = engulfed into cyt + lysed
lifespan varies, 2-5 months in domestic animals
what happens when macrophage engulfs aged erythrocyte
in cyt:
1. broken down + Hb released into cyt
2. Hb broken down to haem, iron + globin
3. globin broken down to aas, reused for production new Hb chains
4. transferrin used transport iron other tissues, stored as ferritin haemosiderin, used again production rbcs
5. haem broken down to bilirubin, released into blood
what happens to bilirubin from breakdown haem
binds albumin in blood, transported liver, taken up hepatocytes, released into bile. into intestine, degraded to urobilinogen, then 1 of 3:
1. degraded to stercobilinogen (brown) -> faeces
2. absorbed intestine, bypasses liver to kidneys -> urine
3. absorbed intestine -> liver, reexcreted in bile
bilirubin yellow colour - causes yellow of jaundice
how is production/release leukocytes stimmed
by inflammatory cytokines from injured/infected areas
major leukocyte types + key purposes
- neutrophils
- monocytes
- lymphocytes - adaptive immunity, can recognise foreign mat + directly destroy or prod antibodies
- eosinophils
- basophils
1 + 2 = innate immunity 1st defence -phagocytosis microbes
4 + 5 = defence against parasites + allergic reactions
granulocytes + agranulocytes
granulocytes = polymorphonuclear w specific cytoplasmic granules + lobulated nuclei - neutrophil, eosinophil, basophil
agranulocytes = mononuclear = no granules in cyt - lymphocytes + monocytes
neutrophils
- lobulated nucleus - 3-5 lobules
- small cyt granules, stained slightly pink - more visible some species, e.g. cow
- proded bone marrow = BM pool -> blood pool (T(1/2) = 5-10hrs) -> tiss pool (few days) by migrating thru endothelium
- bigger than rbcs
wbc behaviour w/in blood pool
- circulating = flowing freely
- marginating = transiently attached endothelium
either or
lymphocytes
- small intermediate + large - large not in dogs, cats
- round, densely-stained nucleus
- scant amount light blue stained cyt = lightly basophilic cyt
- proded BM
- mostly present in + released from lymphoid tissues
- blood pool (varying T(1/2)) -> tiss pool to perform function
- T cells = cell-mediated immunity - lyse cells directly, help other cells perform function
- B cells = antigen recognition + antibody production
- natural killer (NK) cells = cytotoxicity - lyse damaged/foreign cells
monocytes
- similar size neutrophils (or bit bigger)
- variable shaped nucleus
- lightly basophilic cyt (light blue)
- proded BM -> blood pool (T(1/2) 0.5-3days) -> peripheral tissues -> macrophages + dendritic cells (10days-more than year)
- innate immunity = phagocytosis, regulation inflammatory responses
eosinophils
- similar size neutrophils
- lobulated nucleus
- orange/red cyt granules = eosinophilic granules, always distinct
- proded BM -> blood pool (T(1/2) = 8-18hrs) -> tiss pool (weeks-months)
- reg allergic reactions + fight parasitic infections
basophils
- similar size neutrophils
- lobulated nucleus
- purple cyt granules = basophilic granules
- proded BM -> blood pool (T(1/2) 2-3days) -> tiss pool (few days)
- role in allergic reactions
platelets descr
- anucleate cytoplasmic fragments
- pale blue/pink cyt
- clusters purple granules
- originate from big megakaryocyte in BM that tears apart cyt to prod 1000s
- short lifespan 9-10 days
NOT CELLS
function platelets
- clot formation w fibrinogen to stop bleeding
- clot retraction = contraction fibrin mesh to pull edges tiss together
- granules cont vasoconstrictors + growth-promoting prots
heterophils
analogous neutrophil in birds, reptiles + amphibians
* rod-shaped granules not round
* red-orange granules like eosinophils
* most abundant granulocyte (like neutrophils)
thrombocytes
analogous platelets in birds, reptiles, amphibians
* true cell w nucleus
* small amount cyt
* lil bit phagocytic activity asw
overview cellular blood components
table
diff types cartilage + their sub-grps
diagram
2 main components all connective tiss
- cells
- ECM
bvs present asw
what’s present in ECM
- fibrous prots - collagen, elastic, reticular fibres
- non-fibrous glycoprots - cell-ECM interactions
- ground substance (= hydrating gel) - only ordinary + cartilage
ground substance purpose
- medium for exchance substances bet blood + cells
- supports cells + fibres
- binds cells + fibres together
what’s in hydated gel
- glycosaminoglycans (GAGs) = hydrated sugars
- proteoglycans = GAGs attached small prot - huge, high water retention (= no stain well)
derivation CT
fibroblasts
active + large - prod ECM
* prominent nuclei
* basophilic granular cyt (rER) = sign active prot synth
all CT
fibrocytes
dormant, small, maintaining ECM
* condensed, small nuclei
* not proding ECM
* elongated parallel to collagen fibres
* can diff other CT cell types
all CT
structure collagen fibre
triple α-helix chain = mol x10-15 together = fibril x15-20 together = fibre
functions ordinary CT
- mechanical support binding cells together + tiss layers (e.g. epidermis to bone)
- metabolic support - O2 + nutrients bvs w/in tiss to cells by diff thru ECM
- defence
* wbcs migrate into tiss to ‘patrol’
* blood/lymph = liquid CT
* mast cells formed in tissues
mast cell formation + function
basophils leave circulation + form them in tissues
* lots vesicles w vasodilating substances (histamine, serotonin) + proteolytic enzs
* non-self mat = exocyt vesicle conts = local vasodil = greater blood flow = more wbcs
anaphylactic shock = widespread activation so big drop bp
areolar loose CT
in subcut layer skin + under epithelial layer other organs (GI, respiratory, urinary) - diff ones diff amounts each fibre depending function
* collagen fibres strong = tiss high tensile strength
* elastic fibres recoil props so always w collagen limit stretch + prevent tearing
look for lots white spaces to indicate loosely packed cells = loose CT
adipose CT
reserve E source, insulation, protect organs
* adipocytes = modified fibrocytes
* nuclei pushed to periphery as filled fat
* LM = inside cyt ring empty bc fat dissolved in tiss processing
all organs, e.g. abdomen, hypodermis of skin
white adipose tissue (WAT)
no. adipocytes static w constant withdrawal + deposit (so turnover) of lipid
* each adipocyte supported network collagen + reticular fibres
E reserve from stored triglycerides = thermal insulation under epidermis (fat = poor heat conductor)
* also shock absorber in spinal column, feet
reticular fibres need special stain to see LM
brown adipose tiss (BAT)
store E as heat = thermoregulation in proding heat in neonates
* darker bc more mitochond (they release E as heat)
* lots little fat-cont vacuoles, not 1
* nuclei more centrally placed
reticular CT
forms internal skeleton, functions as filtration, e.g. in lymph node
provide support in bv walls + branching networks round cells - made collagen + glycoprot, v v fine
stain w silver stain
dense irregular CT
lots + lots collagen fibres, looks all over the place
w/in all underlying sub-mucosal layers - gut lining, bladder
dense regular CT
collagen/elastic fibres regularly arranged in bundles parallel for max strength
* specific sites like tendons, ligaments
ligaments = bone-bone; tendons = muscle-bone
elastic CT
dense type
for recoil of tiss, e.g. maintain pulsing bloodflow + press in arteries + passive lung recoil
elastin = prot present to provide stretchiness
fibres v thin
basement mem
thin layer glycoprots bind epithelial cells (specific receptors, hemidesmosomes) + then collagen in ECM
* epithelial tiss no blood supply = how nutrients supplied
* cell adhesion
where is hyaline cartilage found
- all joints on long bones - NO fibrous perichondrial layer + v hydrated for cushion compressive forces on bone
- trachea, 1 bronchi - rigid so open all time
- parts skeleton bone no required but inflexible support needed - saves weight but weight-bearing - nasal septum
- end of ribs
how does cartilage grow
- appositional growth - division + activation chondroblasts from fibroblasts in perichondrium = new matrix on surface + build out
- interstitial growth = division chondrocytes in matrix
hyaline cartilage structure w roles
- surrounded perichondrium - dense fibrous CT (mostly irregular)
- chondroblasts secrete ECM then become embedded in semi-solid gel in lacunae = dormant, now chondrocytes
- chondrocytes transparent, smooth + glossy = less friction
- collagen fibres limit amount hydration so swelling so hydrated gel stiff (turgor) for mechanical support
- ECM avascular = diffusion nutrients thru gel for metabolic support
most common cartilage tiss
chrondrocytes shrink in fixation + pull away from sides lacunae
chondroblasts + -cytes in cartilage
present all types
fibrocartilage
fibro + chondro = strong attachment + rigidity, e.g. bet vertebrae
* lots collagen = tensile strength + intervertebral disks subject tensile forces
* chondrocytes in rows bet collagen layers
elastic cartilage CT
lots elastic fibres instead collagen in perichondrium + ground substance = flexible for recoil + movement in organ but still rigid, e.g. ear move in direction sound still maintain shape
functions bone
- support soft tiss + attach sk musc
- structure + anatomy whole bod
- protect internal organs
- mineral homeostasis - stores + releases
- prod bcs from red BM
- triglyceride fat storage as yellow BM
bone cell types
osteogenic cell -> osteoblast (forms matrix in periosteum + endosteum) -> osteocyte (maintains tiss, trapped lacunae)
osteoclast - reabsorption + breakdown ECM, formed fusion macrophages (=multinucleated)
endosteum
cellular layer lining bone cavity
osteoid
organic bony matrix
calcification front
where Ca2+ + electrolytes exocytosed from osteoblasts so added osteoid = matrix becomes hard + calcified + cells trapped -> osteocytes = ossification
osteoclasts how work
release acid to dissolve inorganic matrix + proteolytic lysosomal enzs to breakdown organic matrix - Ca2+ + PO43- to blood
osteoclast purposes
- general turnover bone
- bone remodelling in growth
- fracture repair
- increase blood Ca2+ levels
bone ECM contents
osteoid conts only collagen fibres (resist compression + tension), ground substance, prots bind Ca2+, phosphatases
calcification adds rigidity (support) bc precipitation hydroxyapatite crystals (inorganic)
* cytoplasmic projections osteocytes w gap junctions = communicate
gross anatomy long bone juvenile
BM red when young, old = mostly made fat = yellow
whole thing surrounded periosteum = thin fibrous layer from which cells for repair come
causes osteocyte apoptosis
- reduction mechanical stimulation (astronaut)
- overstimulation - stress fractures
long vs flat bones
long = limbs, ribs; flat = skull, mandible
2 types bone tiss
new bone formation = woven (immature, irregular) - early stages development + repair
develops lamellar (mature, regular, layered) - compact or spongy
compact bone other names + structure
dense, cortical
channels in matrix (Haversian canals) w bv surrounded 2/3 concentric layers (lamellae) matrix + cells = osteon
* metabolic support from bv
* in each layer calcified collagen fibres same orientation but diff direction next lamella = high tensile strength AND resist compression from all directions
mostly long bones - osteons not as well organised flat
spongy bone other names + structure
trabecular, cancellous
bridges outer compact shell of bone w cavity by reinforcing network trabecular rods
* rods present sites greatest stress long bones @ epiphyses, NOT @ diaphysis
* porous + not dense = shock absorber + scaffold for weight bearing
mostly long bones, trabeculae not as well organised in flat
process of bone remodelling
woven -> lamellar
woven = osteoblasts surrounded matrix randomly + collagen fibres random = less strong
- osteoclasts on outer bone surface tunnel + erode through bone = channel for bv to grow
- endosteum (reticular CT) lines tunnels w osteoblasts
- layer osteoid laid, mineralised make bone
- osteoblasts trapped -> osteocytes, occurring in waves inward towards bv = osteon w concentric layers
ossification type flat bones + why
intermembranous - arise in mem of mesenchyme w increased partial press O2
how does intermembranous ossification occur
- grps mesenchymal cells diff into osteoblasts, lay down osteoid islands, calcified to bone
- on surface more cells diff to osteoblasts, lay more matrix
- osteoid islands eventually fuse = woven bone
no cartilage stage
type ossification long bones + vague outline
endochondral/intracartilagenous
* hyaline cartilage template made then replaced woven bone
* blood arrives = higher conc O2 = chondrocytes replaced osteocytes
endochondral ossification
@ 1 centre ossification (diaphysis):
1. cartilage matrix forms shaft centre, calcified + hollows as chondrocytes die (by osteoclasts)
2. cavity filled BM by invading bvs
@ 2 centre @ same time (epiphyses)
* = layer actively growing cartilage each end (physes) for bone lengthening
* when 1 + 2 centres meet lengthening stops + it is adult bone
appositional growth of bone
increase bone diameter
* osteoblasts inner layer periosteum lay new bone (intermembranous ossification)
* whilst osteoclasts erode inner bone surface (= cavity bigger)
joint formation
cystic degeneration mesenchyme bet bone ends by apoptosis
* cruciate ligament surfaces to form synovial lining
giant bone splits smaller
primary + secondary spongiosa
1 = bone spicules w calcified cartilage core
2 = bone spicules w/o cartilage core
resting osteoblasts
flattened cells making up endosteum
* activated = diff into bone-proding osteoblasts
* protect bone + filter blood to send ions + nutrients osteoblasts + osteocytes
present if bone happy + healthy
prepping bone for histological viewing
need to grind down for thin enough to stain
* = dust in gaps, can’t see cellular detail, have to decalcify
