Intro to Histology Flashcards
Lect 2 Week 1 Basu
What is histology?
microanatomy
What is histopathology?
The study of changes in the microscopic anatomy, caused by a disease
What must you use when handling formalin?
GLOVES
What ratio do you use when you are preserving a sample?
1:10 ratio of sample to solution
What does fixation of a sample do?
It hardens and preserves tissue
Some tissue shrinkage occurs
What do you use to fixate a sample?
Formalin
What are the typical histology preparation steps? (6 steps)
Take sample
Fixation
Selection + trimming
Processing + embedding
Sectioning thin slices
Staining to make tissue structures visible
What does selection and trimming include during histology preparation?
Choose your orientation and cut surface
What does processing and embedding include during histology prep?
Replacing water with a solid medium e.g paraffin wax or resin
What solid mediums could you use during the processing and embedding step of histology prep?
Paraffin wax or resin - they replace the water
What is the standard stain?
Haematoxylin and Eosin (H&E)
Describe the dye Haematoxylin:
it is purple/blue and can be considered a BASIC dye therefore it binds to acids e.g. nucleic acids
IT WILL STAIN THE NUCLEI BLUE
Describe the dye Eosin:
it is pink/red and is an acidic dye
and thus it binds to bases, most proteins in the cytoplasm are basic
What are immunohistochemical stains and what do they do?
They use antibodies to bind to a tissue-specific substance and there is a second labelled antibody to bind to first
What labels can be used to attach to the second antibody when using immunohistochemical stains?
Coloured dye or a fluorescent marker
What are the 4 tissue types of the body?
epithelium, connective, muscle, nervous tissue
What does all epithelium tissue rest on?
Basement membrane
Why do epithelial cells rely in diffusion for nutrition?
Because the blood and lymph vessels do not penetrate the basement membrane in which the epithelial cells rest on.
What does the basement membrane act as?
a selective barrier
What two major forms does the epithelium exist in?
surface and glandular
What is surface epithelium?
Sheets of aggregated cells of similar type, covers all EXTERNAL surfaces and lines all INTERNAL surfaces
What is glandular epithelium?
Results from proliferation of surface epithelial cells into underlying tissue and forms secretory cells of endocrine and exocrine glands
What are the three types of surface epithelium?
simple, stratified, pseudostratified
What are the three types of simple surface epithelium?
Squamous, cuboidal, columnar
What are the four types of stratified surface epithelium?
Squamous, cuboidal, columnar, transitional
What is simple surface epithelium?
single layer of cells on basement membrane
what is stratified surface epithelium?
2 or more layers of cells
What is pseudostratified surface epithelium?
appearance of layers but all of the cells are touching the basement membrane, however not every cell is reaching the surface
Function of simple surface epithelium?
As thin barrier e.g. lining of blood vessels, exchange of nutrients
Function of stratified surface epithelium?
Strong resistance to mechanical stress and forces. Increased strength by adding more cells. In physical strength and wear e.g. skin
Describe squamous shape of cells?
scale-like, flat wide cells with greater width than height
Describe cuboidal shape cells?
Cube-shaped, similar height and width
Describe columnar shaped cells?
Height greater than width
Describe transitional shaped cells?
SPECIAL FORM
when epithelium is stretched the cells look squamous
when epithelium relaxed the cells look cuboidal
When are transitional shaped cells useful? In which organ?
For organs that can stretch large amounts. In the bladder (assuming the walls of the bladder)
What extra features do epithelia have?
microvilli, cilia, cellular junctions
microvilli useful for?
absorption in intestine
cilia useful for?
wafting mucus in airways
cellular junctions useful for?
for tight attachments between skin cells. to hold the epithelium cells together so that they are less likely to drop off
What happens when epithelium cells reach the surface of the skin?
they lose the cellular junction and can fall off
cilia are…
motile
SQUAMOUS: give use for a single layer of them and for more than one layer of them.
single: diffusion + filtration
>1: protection
CUBOIDAL/COLUMNAR: give use for a single layer of them and for more than one layer of them.
single: secretion + absorption (ciliated types propel mucus or reproductive cells)
>1: protection
TRANSITIONAL: give use for more than one layer of them.
Protection; stretching to accommodate distension of urinary structures
What is connective tissue derived from?
mesoderm
What does connective tissue form and where is it formed?
It forms a matrix beneath the epithelium
What is the mesoderm?
a layer of tissue inside the embryo during embryonic development
meaning of matrix
a network
what does the connective tissue matrix that forms beneath the epithelium help with?
physically supporting and holding up the epithelium
What is the difference between the epithelium and connective tissue in relation to number of cells:
connective tissue has relatively few cells unlike the epithelium
what is connective tissue mainly made up of?
extracellular matrix
Name two ‘things’ that are found within the extracellular matrix:
Protein fibres
Ground substance
What is the connective tissue a medium for?
exchange of nutrients and waste
2 functions of the connective tissue:
provide structural support to other tissue
mediate the exchange of nutrients and waste
What are protein fibres mainly made up of?
collagen
What properties does collagen give protein fibres?
great tensile strength
What gives connective tissue its strength?
The long protein fibres which are mainly made from collagen
What two fibres make up connective tissue?
collagen and elastic fibres
What do the elastic fibres allow?
stretch and elasticity
What are the elastic fibres composed of?
elastin
What is the advantage of elastic/protein fibres for the connective tissue?
strong (due to protein fibres/collagen) but also stretchy tissue that can bounce back
under the microscope, what colour can collagen show up as?
black
What is ground substance?
gel-like material that is transparent
What does ground substance do?
it fills spaces between cells and fibres
How many different sub-types of collagen fibres are there?
five
What % of collagen fibres are type 1?
90%
What do the collagen fibres do?
add structural integrity to our tissue
What is ground substance made up of?
made up of many large molecules called glycosaminoglycans GAGS
What does GAGS stand for?
glycosaminoglycans
Describe GAGS flexibility:
inflexible
Describe GAGS attraction to water:
very hydrophilic
What are they called when multiple GAGS are linked up?
proteoglycans
90% of extracellular matrix is what?
water
What are GAGS good at binding to?
water
What are GAGS very good at resisting and give two reasons why?
Good at resisting compressive forces due to its high water content and because they are inflexible.
(think, pushing water out of syringe easy, but if you cover the end of the syringe, impossible to push because water is very good at resisting compressive forces and because GAGS absorb a lot of water, like sponge, they too are good at resisting compressive forces)
What does the ground substance facilitate?
movement of cells (macrophages, immune cells) and diffusion of molecules e.g. oxygen
Name four types of cells that around found in the connective tissue:
fibroblasts
adipocytes
immune cells
other specialised cells
Firboblasts found throughout:
most tissues in body
what are adipocytes?
fat cells
name three immune cells:
macrophages
mast cells
plasma cells
immune cells go around the… looking for foreign etc.
extracellular matrix
give 4 example of the other specialised cells that could be found in the connective tissue:
osteocytes, osteoblasts, chrondocytes, chrondoblasts
osteo =
bone
chrondo =
cartilage
What are fibroblasts?
the least specialised cells, they secrete collagen and ground substance
