modern anatomy spans scales - from cells to systems via tissues and organs

Question 1

how many systems does the human body have

Answer 1

11

Question 2

resolution

Answer 2

smallest distance between 2 points that can be distinguished as 2 separate objects

Question 3

light microscope can distinguish

Answer 3

whole cells and largest organelle - nucleus

Question 4

to preserve a tissue/cell what do you have to do

Answer 4

fixation

Question 5

to resolve tissue organisation, specimen should be

Answer 5

thinner than typical cell to allow light to penetrate
-thicker specimens would give a blurred image, difficult to interpret

Question 6

haematoxylin (dark blue) stains negatively charged structures such as

Answer 6

DNA, RNA so nuclei

Question 7

eosin (red) - acidic dye which stains positively charged structures such as

Answer 7

cytoplasm, cellular proteins

Question 8

electron microscope - high resolution due to

Answer 8

very short wavelengths

Question 9

TEM

Answer 9

electron beam is passed through specimen generating a projection image on a sensor
-view ultrathin specimens (tissue sections)

the structure of
purified protein molecules (contrasted by metal shadowing), the organization
of molecules in viruses and cytoskeletal filaments (prepared by a negative
staining technique), and the arrangement of protein molecules in cell
membranes (by freeze-fracture).

Question 10

SEM

Answer 10

electron beam fired at surface of specimen
-used to study topography of specimens

Question 11

why are specimens treated with a fixative (3)

Answer 11

-stop metabolism
-make macromolecules insoluble by denaturing
-inactivate degradative enzymes

Question 12

common fixative solution used to treat specimens

Answer 12

solution of neutral buffered formaldehyde (CH2O)

Question 13

how to cut thin sections - solution

Answer 13

support tissue by freezing water or replacing water with more supportive medium, e.g. wax

Question 14

how to cut thin sections - replacing water with more supportive medium eg. wax:

Answer 14

1. replace water in tissue with Paraffin wax. wax can’t mix with water, so dehydrate tissue in ethanol solutions of increasing strength (70%, 96%, 100%-“graded alcohols”)
2. replace ethanol with xylene. Paraffin wax can’t mix with ethanol so put tissue in an organic solvent common to both ethanol and
   wax e.g. xylene
3. wax - infiltrate tissue with molten wax until wax fills space previously filled with water, both between, and within, cells

after cooling and solidifying, the waxembedded tissue is cut into thin
sections using a MICROTOME with a steel
knife.
* The wrinkled section is flattened by floating
in warm water and then picked up on a
glass slide

Question 15

stains = aqueous
solutions immiscible with wax
SOLUTION =

Answer 15

rehydrate, wax no longer needed as section is cut and supported on glass slide
-Remove the wax from the tissue on the section using xylene/toluene
- rehydrated section using ethanol solutions of decreasing strength (100%, 95%, 70%, water). Going straight into
water would cause severe distortion.
- Section is ready to stain

Question 16

electron microscope uses beams of …. instead of light as illuminating radiation

Answer 16

electrons

Question 17

Challenge: Cellular components differ little in their absorption of
light so tissue sections are almost invisible using ordinary
microscopes
WHAT IS THE SOLUTION

Answer 17

Treat section with stains that bind selectively to different structures
making them different colours

Question 18

highest resolution to lowest resolution microscopy

Answer 18

highest = TEM
then SEM
lowest = light microscope

Question 19

organism –> tumour –> biopsy (tissues/cells) –> ……

Answer 19

molecular characterisation