Lab 3 - epithelial tissue: structural and functional analysis Flashcards
MGPY
methyl green (MG) is specific stain for DNA staining it greenish blue whily pyronin (PY) stains RNA pink
staining around the nucleus due to mRNA (pink) and there will also be some staining in the cytoplasm (pink) from free ribosomes)
H and E stain colours
basic = pink acidic = purple
Fixatives
preserve nucleic acids in a state suitable for staining, do not give very good preservation of general structure
Role of acinar (exocrine) cells of the pancrea
to secrete digestive enzymes into the GI tract
What organelles are inside acinar cells
Ribosomes (rER)
Golgi body (package and also to send out the apical pathway)
Mitchondira
Many zymogen granules at the apical region of the cell
Distribution of DNA and RNA in the acinar cells
DNA = present only in the nucleus RNA = present in the nucleolus, also present in free ribosomes and polyribosomes, as well as rER
MGPY stain and apical regions
staining will be absent from apical regions as this is where the zymogen granules are located, which is protein, and therefore the MGPY stain leaves a ‘clear area’
Zymogen granule location
generally clustered apically for secretion into the lumen of the duct
H&E and acinar cell
Pink in cytoplasm, purple nucleus and purple border due to nuclei basally
MGPY and acinar cell
Doesnt stain symogens
Blue nucleus
Pink cytoplasm
RNA mainly in the cytoplasm being translated at rER which is basal
Toluidine blue and acinar cell
Zymogen granules stained deep blue
Amylase
a major secretatory protein that is stored in pancreatic zymogen granules for secretions
rER in acinar cells
makes the proteolytic enzymes
golgi in acinar cells
packages proteolytic enzymes into vesicles
zymogen granules in acinar cells
they are released into ducts
If tissues are stained with heavy metals…
contrast will increase
TEM
very useful for gaining information about cellular ultrastructure to the molecular level
Function of the duct
the duct carries away the digestive enzymes from the acinar cells where they are produced, to be released into the duodenum of the small intestine
Pancreatic duct cells are also able to secrete bicarbonate to neutralise acidic contents that enter the duodenum from the stomach
Endocrine role of prancrea
secretes insulin and glucagon into the bloodstream
Simple squamous …
flattened soma, squashed but bluging nuclus
thin for diffusion so would be found in the lining of a blood vessel
Cuboidal epithelial
square shaped cell, centrally placed nucleus
lining a duct, for structure
Tight junctions
prevent the unwanted transfer of substances to and from the lumen of the vessel and between cells
Junctional complexes
to allow for parallel connections between adjacent cells
zonula adherens
desmosomes
Tight junctions
TAD
Capillary
simple squmous
only tight junctions to not let out blood
Lumen of the duct
Microvilli inside
Simple cuboidal
ZOnula adherens, desmosomes and tight junctions
Microvilli function
increase surface area for absorption/secretion and it is found in the small intestine, in the nephron
CIlia function
move substances on apical surface and it is found in the respiratory tract, reproductive system
Microvilli features
0.5-1 microm in length
parallel bundles of actin microfilaments which insert into the terminal web of the cytoskeleton which are anchored perierally to the zonula adherens
Cilia features
motile or non-motile (for sensory infor)
up to 10 microm in length - half the length of the cell
each cilium is surrounded by a plasma membrane and contains a central core - the axoneme. this consists of 20 microtubules arranged with one central doublet and 9 peripheral doublets. these are linked by proteins called nexin. Each microtubule has arms made of the protein dynein
Dynein catalyses the conversion of ATP to ADP results in bending of the doublets to create a wave like motion
Two ways you could distinguish microvilli and cilia
size relative to the rest of the cell
different structure visible in the EM images i.e. the anchorings of the structures
Anchoring of cilia and microvilli
cilia = well anchored below the plasma membrane
microvilli = anchored quire superficially on the plasma membrane
Cilia are only present on
pseudostratified epithelia
esophagus =
stratified sqaumous epithelia
trachea =
pseudostratidied ciliated (columnar) epithelium
nucleus stains - H&E, MGPY and toluidine blue
1 - purple (dark)
2- blue/green
3 - N/A unstained
