Epithelia and supporting tissue lecture - week 2 Flashcards
What are the four basic tissues?
- epithelial tissue
- supporting tissue
- msucular tissue
- nervous tissue
Define epithelial tissues
- diverse group of tissues including surface epithelia and solid organs
Where can epithelial tissues be found?
surface epithelia cover and line all body surface, cavities and tubes - interface between different compartments
What processes are epithelial tissues involved in?
containment, selective diffusion, absorption, secretion, physical protection
What do all epithelial tissues contain?
cytokeratin intermediate filaments - makes them recognisable on immumohistochemistry
What supports all epithelia cells?
by a basement membrane of variable thickness
What does the basement membrane do?
- separates the epithelium form the underlying supporting tissue
- does not contain blood vessels so epithelium is dependent on diffusion of nutrients and oxygen from connective tissue for survival
Are epithelial cells polarised?
yes
How are epithelial cells polarised?
with one side facing the basement membrane (basal surface) and one towards the surface (apical surface)
How are surface epithelial cells classified?
- according to number of cell layers
- shape of the component cells
- presence of surface specialisations
What is a simple epithelial cell?
single layered
What is a multilayered epithelial cell?
stratified
Name different shapes an epithelial cell can have
squamous - flattened
cuboidal or columnar
Name 4 types of simple epithelial
- simple squamous epithelium
- simple cuboidal
- simple columnar
- pseudo stratified columnar ciliated epithelium
What is the structure of a simple squamous epithelium?
flattened irregular shaped cells forming a continuous surface surface - pavemented epithelium
What is the BM of a simple epithelia?
delicate underlying basement membrane
Name examples for when simple epithelia is used
lining surfaces involved in diffusion of gases eg. lungs or fluids eg. blood capillaries
How do simple epithelia look like?
cells are so flat they can only be recognised by nucleus which bulges into lumen
What is the simple cuboidal epithelia?
the intermediate between simple squamous and simple columnar
What about the nucleus of simple cuboidal epithelia cells?
nucleus Is round and located in the centre of the cell
Where can simple cuboidal cells be found?
lines small ducts and may have excretory, secretory or absorptive functions eg. collecting tubules of kidney
How can you identify a simple cuboidal epithelial cell ?
cell border may be distinct, nuclei give away - very big
What are simple columnar epithelial cells like compared to the others?
like simple cuboidal but cells are taller
Where is the nuclei located in the cell of the simple columnar epithelial cell?
nuclei elongated, may be located towards base, apex or centre of the cytoplasm - this is the polarity of the nucleus
Where are simple columnar epithelial cells found?
on absorptive surfaces eg. small intestine, gall bladder (absorbs water) or play a secretory role eg. stomach
What do simple columnar epithelial cells look like?
long rectangles, nucleus all towards one side of the cell
What is a pseudo stratified columnar ciliated epithelium ?
- true simple epithelium because all cells rest on basement membrane, but nuclei are all at different levels giving the appearance of different cell layers
Where are pseudo stratified columnar collated epithelium cells found?
confined to airways so known as respiratory epithelium: cilia propel mucous to pharynx = muscociliary escalator
What is the main function of stratified epithelia?
mainly a protective function
Why are stratified epithelia cells poorly sited for absorption and secretion?
due to thickness of all the cell layers
Name two kinds of stratified epithelia cells
- stratified squamous epithelium
- transitional epithelium (urethelium)
Where are transitional epithelium (urethelium) found?
only in the urinary tract in mammals
What is the function of transitional epithelium (urethelium)?
highly specialised to accommodate stretch and toxicity of urine
Where is the transitional epithelium located?
intermediate between stratified cuboidal and squamous epithelia
How do transitional epithelium cells look like?
- relaxed: surface cells are large and round
- stretched: intermediate and surface layers are extremely flattened
Name two types of membrane specialisations of epithelia?
cilia, microvilli, goblet cells
What are cilia?
motile structures that protect forms he luminal surface of the epithelial cells,
Where are cilia found?
notably int eh female reproductive and respiratory tract
are cilia seen under a light microscope?
yes, easily
How do cilia move?
beat with a wave-like synchronous rhythm propelling particles / fluid in a consistent direction over the epithelia surface
How long can cilia be ?
10 micrometers long
How many cilia might be on a cell?
300 cilia