Histology Flashcards
done to 24
1
Q
4 tissue types
A
epithelial, connective, muscle, nervous
2
Q
define histology
A
study microscopic structure of tissue
branch of anatomy
essential for understanding function, abnormalities + pathological change
3
Q
avg cell mem thickness
A
7.5nm
4
Q
nucleus + nucleolus diameter
A
4µm 1µm
5
Q
length mitochondrion + width cilium
A
0.5 - 4µm 250nm
6
Q
resolution LM + EM
A
w/in 0.2µm 0.5nm
7
Q
plasmalemma
A
pm bounding cell, esp directly inside plant cell wall
8
Q
steps tissue processing
A
- fixation
- embedding
- sectioning
- mounting
- de-waxing
- staining
9
Q
describe fixation process
A
- 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
10
Q
why fixation
A
prevent rotting - bac/fungal attack; autodigestion by enzs leaking out lysosomes
11
Q
how fixation works
A
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
12
Q
embedding process
A
poor on wax (LM) / resin (EM) to provide scaffolding for support in sectioning
13
Q
problems w tissue processing
A
- heating + dehydration can damage/alter tissue structure, e.g. shrinkage/tearing
- hardening tissue by freezing but icicles, then melt = holes
14
Q
sectioning process
A
using sharp microtome, wanting 1 cell thick (5-7µm), LM or 1 organelle (100nm), EM - best if makes continuous ribbon
15
Q
process mounting
A
slide slide under ribbon floating in water
16
Q
de-waxing process
A
reverse fixation
* xylene dissolves wax
* 100% alcohol to remove xylene
* decreasing alcohol conc sols to water
17
Q
why de-waxing
A
- not natural part tissue so needs removal before viewing
- most conventional stains waterbased so need for stain penetrate
18
Q
routine LM stain
A
Haemotoxylin + Eosin (H+E)
every prot in cyt -> pink so cyt pink
19
Q
why staining necessary
A
cells pretty much colourless
20
Q
why nucleus visible
A
histone prots fixed in place + NAs coiled around (forming chromatin)
21
Q
histochemical stains
A
specific - used highlight certain parts cell, e.g. enzs or chemical components
22
Q
trichrome
A
23
Q
how stains work EM
A
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
24
Q
common EM stain
A
Osmium tetroxide (OsO4) - stain + fixative
stabilises lipids so e- dense + black = visible = specialised stain
25
description + purpose myelin sheath
concentric layers myelin (lipid) around axon to:
1. protect
2. insulate
3. make more efficient at conducting
26
When to change light intensity on LM
increased mag = smallr specimen field = more light required
| and vice versa
## Footnote
= turn up lamp + widen diaphragm
27
epithelial tissues
form barrier bet other body tissues + internal/external environ across which all exchanges take place, defending underlying tissues
28
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)
29
2 types epithelia
1. simple = single layer cells
2. stratified = multiple cell layers
30
purpose basal lamina in epithelia
attachment structure to allow attachment ep cells to connective tissue
31
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
32
basolateral surface
surface that adjoins underlying tiss
33
type anchoring cell junctions
desmosomes for cell-cell attachment
hemidesmosomes attach cell to basement mem
| multiprot complexes to facilitate adhesion
34
where simple epithelia found + why
found only internal protected surfaces bc too delicate constitute defensive barrier against mechanical damage (as single layer)
35
types simple epithelia
1. squamous
2. cuboidal
3. columnar
4. pseudostratified
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types stratified epithelia
1. squamous
* squamous
* keratinised
* parakeratotic
2. transitional
37
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
38
endothelium
epithelium internal lining blood vessels - simple squamous
39
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
40
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
41
how simple columnar epithelium specialised secretion
no apical specialisations but goblet cells can sweel w mucus (lubricant)
42
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
43
how simple columnar epithelium specialised move mats over epithelial surface
cilia, e.g. airways
44
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
45
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
46
how are stratified epithelia classified (named)
superficial layer gives rise to naming
47
rete pegs
peg-like downgrowths from lowest layer cells into underlying connective tissue to attach
48
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
49
cornification
formation layer dead cells w/o cellular detail filled w keratin
50
keratin
* physically strong, chemically inert, semi-waterproof
* forms epidermis + protects mech damage, chem damage, dessication
* allows retain shape
51
epidermis
epithelial layer of skin
52
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
53
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
54
oblique section demonstrated
55
single secretory cells found?
scattered in simple epithelia = individual exo/endocrine cells, e.g. goblet cells
56
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
57
embryological origin endocrine glands
1. derived mesodermal layer + don't retain connection w epithelium, e.g. thyroid
2. 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
58
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
59
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
60
classification exocrine glands based shape
1. simple
2. compound
61
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
62
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
63
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)
64
classification exocrine glands based secretion type
1. serous - alveolar units
2. mucous - tubular units
3. seromucous (mix)
65
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
66
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
67
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
68
classification exocrine glands based mode of release
1. merocrine
2. apocrine
3. holocrine
69
merocrine gland descr
vesicle releases secretory products into duct via exocyt
70
apocrine gland descr
mem-bound vesicle pinched off (w some cytoplasm) + deposited on epithelial surface
71
holocrine gland descr
entire cell sheds into duct then dying cell pm ruptures, releases secretory products
* formation replacement cells
72
endocrine gland structure
each gland own morphology
sometimes cells aggregated around caps, e.g. islets Langerhans in pancreas prod insulin + glucagon
73
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)
74
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)
75
adrenal gland structure
2 main parts w diff functions
1. adrenal medulla
2. adrenal cortex
76
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
77
adrenal cortex structure + function
gland conts cells for synth + release hormones w 3 areas
1. zona glomerulosa
2. zona fasciculata
3. zona reticulata
78
zona glomerulosa
* secretes mineralocorticoids - aldosterone
* signals from kidneys - reabsorb Na+ for water + electrolyte balance
79
zona fasciculata
* secretes glucocorticoids, e.g. cortisol, increasing in response to stress
* signals from hypothalamus + pituitary
* pale-staining as prod steroids from lipid
80
zona reticulata
* secretes sex steroids (androgens, sex hormones)
* signals from hypothalamus + pituitary
81
myogenesis
process all muscle cell types from in embryogenesis
82
myocyte
= mucle cell = muscle fibre = myofibre
* characteristically long + fibre-like, arranged parallel direction contraction
83
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)
## Footnote
CT for insulation
84
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
85
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
86
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
87
sarcomere
| = contractile unit
dist bet 2 z-discs/z-lines @ centre I band
88
myofibrils
parallel arrangements thread-like elongated structures running whole length sarcoplasm myocyte
* have 2 myofilament types
1. thick myosin
2. thin actin
89
structure myosin filament in sk musc
made myosin prots, each w 2 globular heads + tail
* heads have binding sites actin + ATP + some ATPase activity
90
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
91
contraction sk
1. influx Ca2+ from SR binds troponin on actin myofilament
2. conformational change troponin = tropomyosin unbinds actin
3. myosin binding sites exposed = actin-myosin interaction
4. E released at same time + myosin head pulls attached actin towards centre sarcomere
5. sarcomere shortened + muscle cell contracted
6. myosin head binds new ATP, detaches actin, lengthens, repeat
92
muscle spindle
stretch-responsive sensory receptor - receives input to stretch + immediately contracts + sends feedback CNS
| modified muscle fibre
93
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
94
structure cardiac myocytes
* joined at ends by intercalated discs
* not syncytium
* cells may branch
* central nuclei
* striated
* more + larger mitochondria due more aerobic resp
95
how can cardiac muscle maintain contractions over long time
t tubs more developed + release more Ca2+
96
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
97
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
98
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
99
regeneration smooth myocytes
pericytes = undiffed cells
1. hyperplasia (increase cell nos)
2. hypertrophy (increase cell size)
100
criteria to be lymphoid organ
need partial or complete connective tissue capsule surrounding organ
| otherwise accessory lymphoid tissue
101
primary vs secondary lymphoid organs
1. where lymphocytes receive immunocompetence (bone marrow (B) + thymus (T)) = site maturation
2. receive lymphocytes, e.g. lymph nodes, spleen, tonsils
102
non-specific, innate immune defences
1. skin + mucous mems - protective surfaces/secretions
2. internal defences - inflammation, phagocytosis
| specific is acquired or adaptive
103
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)
104
secondary lymphoid tissue
* tonsils
* Peyer's patches = gut associated lymphoid tissue (GALT)
* mucosal associated lymphoid tissue (MALT)
* broncheal associated lymphoid tissue
....
105
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
106
Hassall's corpuscles
in medulla THYMUS ONLY - epithelial cells concentrically surrounding cell debris
| look like roses
107
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
108
clinical importance lymph nodes
enlarge when activated by infection so swelling indicates disease
109
germinal centres lymph node
at centre nodules (follicles) in cortex - where B + T cells proliferated + activated
110
trabecula
CT going into lymph node (+ others, not thymus) from external capsule for structural support
111
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
112
spleen function
filter blood - involved immunosurveillance in left abdomen
113
spleen basic structure
* red pulp - mostly rbcs
* white pulp - wbcs (B, T, macrophages) (purple in stain)
114
tonsil structure
* no capsule
* lined oral epithelium
* follicles w B-cell germinal centres when stimmed antigens (all the time)
115
cellular els of blood + purposes
1. erythrocytes for gas exchange to transport O2 + CO2 bet lungs + peripheral tissues
2. leukocytes for defence against infectious + injurious agents
3. platelets/thrombocytes to stop bleeding (= haemostasis
116
plasma
sol of blood in which cells dispersed made water + plasma prots
117
plasma prots + purpose
1. albumin
2. 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
118
functions plasma
1. transport nutrients, hormones, waste products, heat
2. homeostasis - maintain blood fluidity, pH, water content
119
serum
plasma but w/o clotting factors (inc fibrinogen)
120
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)
121
haematopoietic cells
multipotent, primitive + can develop any type blood cell
122
types bone marrow
1. red marrow = mostly haematopoietic cells, mostly in long, flat bones - spine, hips, sternum
2. yellow marrow = mostly fat cells, can be converted haematopoietic lines
123
maturation erythrocytes
lose organelles inc nucleus -> anucleate, biconcave discs = erythropoiesis
* in bone marrow, final stage whilst circulating in blood
| anucleate = no nucleus
## Footnote
stain pink due Hb
124
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
125
variation colour rbc
| beyond normal small amount
polychromasia
126
variation in rbc size
| beyond small normal amount
anisocytosis
127
variation in shape rbc
| beyond normal small amount
poikilocytosis
128
prominent central pallor rbc
hypochromia = hypochromasia, possibly indicating reduced Hb conc
129
role carbonic anhydrase in gas exchange
facilitates transport O2 + CO2
130
how can rbc carry O2
adult Hb has 2α + 2β chains, each w Fe-cont haem grp that can bind 1O2 mol
131
how is structure foetal Hb diff from adult + why
2γ chains instead of β, giving higher affinity O2, enabling placental O2 transfer
132
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
133
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
134
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
135
how is production/release leukocytes stimmed
by inflammatory cytokines from injured/infected areas
136
major leukocyte types + key purposes
1. neutrophils
2. monocytes
3. lymphocytes - adaptive immunity, can recognise foreign mat + directly destroy or prod antibodies
4. eosinophils
5. basophils
1 + 2 = innate immunity 1st defence -phagocytosis microbes
4 + 5 = defence against parasites + allergic reactions
137
granulocytes + agranulocytes
granulocytes = polymorphonuclear w specific cytoplasmic granules + lobulated nuclei - neutrophil, eosinophil, basophil
agranulocytes = mononuclear = no granules in cyt - lymphocytes + monocytes
138
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
139
wbc behaviour w/in blood pool
1. circulating = flowing freely
2. marginating = transiently attached endothelium
| either or
140
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
1. T cells = cell-mediated immunity - lyse cells directly, help other cells perform function
2. B cells = antigen recognition + antibody production
3. natural killer (NK) cells = cytotoxicity - lyse damaged/foreign cells
141
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
142
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
143
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
144
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
145
function platelets
1. clot formation w fibrinogen to stop bleeding
2. clot retraction = contraction fibrin mesh to pull edges tiss together
3. granules cont vasoconstrictors + growth-promoting prots
146
heterophils
analogous neutrophil in birds, reptiles + amphibians
* rod-shaped granules not round
* red-orange granules like eosinophils
* most abundant granulocyte (like neutrophils)
147
thrombocytes
analogous platelets in birds, reptiles, amphibians
* true cell w nucleus
* small amount cyt
* lil bit phagocytic activity asw
148
overview cellular blood components
| table
149
diff types cartilage + their sub-grps
| diagram
150
2 main components all connective tiss
1. cells
2. ECM
| bvs present asw
151
what's present in ECM
* fibrous prots - collagen, elastic, reticular fibres
* non-fibrous glycoprots - cell-ECM interactions
* ground substance (= hydrating gel) - only ordinary + cartilage
152
ground substance purpose
* medium for exchance substances bet blood + cells
* supports cells + fibres
* binds cells + fibres together
153
what's in hydated gel
1. glycosaminoglycans (GAGs) = hydrated sugars
2. proteoglycans = GAGs attached small prot - huge, high water retention (= no stain well)
154
derivation CT
155
fibroblasts
active + large - prod ECM
* prominent nuclei
* basophilic granular cyt (rER) = sign active prot synth
| all CT
156
fibrocytes
dormant, small, maintaining ECM
* condensed, small nuclei
* not proding ECM
* elongated parallel to collagen fibres
* can diff other CT cell types
| all CT
157
structure collagen fibre
triple α-helix chain = mol x10-15 together = fibril x15-20 together = fibre
158
functions ordinary CT
1. mechanical support binding cells together + tiss layers (e.g. epidermis to bone)
2. metabolic support - O2 + nutrients bvs w/in tiss to cells by diff thru ECM
3. defence
* wbcs migrate into tiss to 'patrol'
* blood/lymph = liquid CT
* mast cells formed in tissues
159
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
160
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
161
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
162
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
163
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
164
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
165
dense irregular CT
lots + lots collagen fibres, looks all over the place
w/in all underlying sub-mucosal layers - gut lining, bladder
166
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
167
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
168
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
169
where is hyaline cartilage found
1. all joints on long bones - NO fibrous perichondrial layer + v hydrated for cushion compressive forces on bone
2. trachea, 1 bronchi - rigid so open all time
3. parts skeleton bone no required but inflexible support needed - saves weight but weight-bearing - nasal septum
4. end of ribs
170
how does cartilage grow
1. appositional growth - division + activation chondroblasts from fibroblasts in perichondrium = new matrix on surface + build out
2. interstitial growth = division chondrocytes in matrix
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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
## Footnote
chrondrocytes shrink in fixation + pull away from sides lacunae
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chondroblasts + -cytes in cartilage
present all types
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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
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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
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functions bone
1. support soft tiss + attach sk musc
2. structure + anatomy whole bod
3. protect internal organs
4. mineral homeostasis - stores + releases
5. prod bcs from red BM
6. triglyceride fat storage as yellow BM
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bone cell types
osteogenic cell -> osteoblast (forms matrix in periosteum + endosteum) -> osteocyte (maintains tiss, trapped lacunae)
osteoclast - reabsorption + breakdown ECM, formed fusion macrophages (=multinucleated)
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endosteum
cellular layer lining bone cavity
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osteoid
organic bony matrix
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calcification front
where Ca2+ + electrolytes exocytosed from osteoblasts so added osteoid = matrix becomes hard + calcified + cells trapped -> osteocytes = ossification
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osteoclasts how work
release acid to dissolve inorganic matrix + proteolytic lysosomal enzs to breakdown organic matrix - Ca2+ + PO43- to blood
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osteoclast purposes
1. general turnover bone
2. bone remodelling in growth
3. fracture repair
4. increase blood Ca2+ levels
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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
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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
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causes osteocyte apoptosis
* reduction mechanical stimulation (astronaut)
* overstimulation - stress fractures
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long vs flat bones
long = limbs, ribs; flat = skull, mandible
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2 types bone tiss
new bone formation = woven (immature, irregular) - early stages development + repair
develops lamellar (mature, regular, layered) - compact or spongy
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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
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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
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process of bone remodelling
woven -> lamellar
woven = osteoblasts surrounded matrix randomly + collagen fibres random = less strong
1. osteoclasts on outer bone surface tunnel + erode through bone = channel for bv to grow
2. endosteum (reticular CT) lines tunnels w osteoblasts
3. layer osteoid laid, mineralised make bone
4. osteoblasts trapped -> osteocytes, occurring in waves inward towards bv = osteon w concentric layers
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ossification type flat bones + why
intermembranous - arise in mem of mesenchyme w increased partial press O2
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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
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type ossification long bones + vague outline
endochondral/intracartilagenous
* hyaline cartilage template made then replaced woven bone
* blood arrives = higher conc O2 = chondrocytes replaced osteocytes
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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
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appositional growth of bone
increase bone diameter
* osteoblasts inner layer periosteum lay new bone (intermembranous ossification)
* whilst osteoclasts erode inner bone surface (= cavity bigger)
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joint formation
cystic degeneration mesenchyme bet bone ends by apoptosis
* cruciate ligament surfaces to form synovial lining
| giant bone splits smaller
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primary + secondary spongiosa
1 = bone spicules w calcified cartilage core
2 = bone spicules w/o cartilage core
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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
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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
