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normal structure + function > histology > Flashcards

histology Flashcards

1
Q

what is histology

A

study of microscopic structure of tissues to identify morphological changes in tissues that characterise disease to allow for accurate diagnosis

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2
Q

why study histology

A

essential for understanding function + pathological change to allow for accurate diagnosis. need to identify components in normal tissues

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3
Q

what is a cell

A

basic functional unit of all multi-cellular organisms

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4
Q

steps in tissue processing

A

1) fixation (dehydration + clearing )
2) embedding
3) sectioning

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5
Q

what is fixation

A

fixation preserves architecture by treating it with a chemical reagent. this holds tissue components in normal place and prevents tissue from rotting due to bacteria/fungus or autodigestation by enzymes leaking for lysosomes

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6
Q

how do fixatives work

A

they have binding sites enable them to form cross-links between adjacent tissue protiens = fixed shape. they protect from digestion by binding and inactivating microbes at spare binding site

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7
Q

what is the most common fixative

A

formaldehyde

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8
Q

what is a limitation of fixation

A

preserves proteins but not all other important cell components

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9
Q

what are the stages of fixation

A

dehydration and then clearing
dip tissue in increasing concentrations fo alochol starting at 50% going to 100% and then clearing - dip in xylene to completely remove water

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10
Q

what do you embed it in

A

wax or resin

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11
Q

how do you embed

A

place tissue in mould and pour wax in and solidify .
for electron microscope use resin

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12
Q

what happens during sectioning

A

fit wax into block and use knife to slice into thin slices using a microtome ( thinner = clearer)

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13
Q

differences between light microscope and electron microscope sections

A

for light microscope - wax sections, 4um + metal blade
for electron - resin sections, 100nm + diamond knife

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14
Q

what happens if blade is blunt for sectioning

A

crumpled sections (should have ribbons)

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15
Q

what happens during mounting

A

sections are floated on water and then mounted on a glass slide

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16
Q

what happens during dewaxing

A

opposite of fixation - to remove chemicals. use xylene to remove wax then go from 100% alcohol to 50% until water to remove xylene and reintroduce water

17
Q

what are the routine stains for a light microscope

A

haematoxylin - purple, basic stain nuclei goes purple
eosin - acidic stain, protein goes red/pink

18
Q

what do epithelial tissues do

A

cover and line internal + external surfaces of bodies , forming a barrier between other body tissues and internal/external environments across which all exchanges take place. Defends tissues.

19
Q

Features that are common to all epithelial tissues x5

A

1) totally cellular (no connective fibres, only cell junctions)
2) no blood vessels
3) have stem cells within = self-regenerating
4) separated from underlying tissues by basal lamina
5) supported by underlying layer of connective tissue (mechanical support) which contains blood vessels (metabolic support)

20
Q

2 main types of epithelia

A

simple - single cell layer
stratified - multiple layers of cell

21
Q

What type of organisation do epithelial cells have

A

polarised = always attached to basal lamina and have a free surface towards cavity (apical)

22
Q

define lumen

A

empty space within tubular organ

23
Q

3 types of cell junctions

A

1) occluding = barrier, tight junction
2) anchoring = strength, desmosomes and hemidesmosomes (attach to basal lamina)
3) communicating = movement between cells, gap junction

24
Q

types of simple epithelia x4

A

squamous, cuboidal, columnar and pseudostratified

25
Q

types of stratified epithelia x2

A

squamous (squamous, keratinised and parakeratotic) and transitional

26
Q

simple squamous epithelium structure + function

A

-single layer due to thin cytoplasm
-flattened nucleus + indistinct cytoplasm
-slick surface to allow flow of fluid
-irregular boundaries
-allow rapid transport (gas exchange)
-low-friction (cover internal organs)

27
Q

structure + function of cuboidal epithelium

A
  • single layer
  • cell height ,width +depth are same
    -centrally placed nucleus
  • cover internal surfaces
    -cover duct walls (glands for secretion)
    -equal cytoplasm around nucleus
  • no synthetic activity (except thryoid)
28
Q

structure and function of simple columnar epithelium

A
  • cell height is more than width
    -nucleus arranged in ordered layer
  • no apical specialisations (top end)
    -specialised for absorption and secretion (digestive system)
    -nucleus towards basal membrane
29
Q

types of apical specialisation for columnar epithelium

A

-microvilli (intestine) for absorption, bigger sa
-cilia (airways) draft particles away, move over epithelial surface, gaps

30
Q

structure + function of pseudostratified columnar epithelium

A
  • nuclei at different levels but still SINGLE layer (all in contact with basal lamina
  • ciliated
    -restricted to respirator system ( goblet cells = cells that secrete mucus)
31
Q

stratified squamous epithelium

A
  • basal layer is cuboidal
  • upper layers are squamous
  • defence against mechanical damage (oral cavity, oesophagus, skin)
    -integrity provided from desmosomes
  • attachment by rete pegs (projections at basal lamina)
32
Q

keratinised stratified squamous structure + function

A
  • upper layers = squamous and keratohyalin (protein granules)
  • superficial (outermost) layer = no cellular detail + keratin (red)
  • epidermis = protect from mechanical damage + dessication (drying out)
    -strong, semi-waterproof + chemically inert
33
Q

parakeratotic stratified squamous structure + function

A
  • ruminant forestomach only
    -top layer = cellular detail + keratin
  • protection from coarse ingesta
  • absorbs fermentation products (VFA)
34
Q

transitional epithelium structure and function

A
  • can stretch
  • superficial layers are fatter and rounder ( look like frog spawn)
    -no keratin or rete pegs
  • urinary system only
    -stretches when bladder fills (tips when stretched look squamous, form troughs when relaxed)

normal structure + function (9 decks)

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