Epithelial Tissue Flashcards
what are some features of epithelial tissue
- lines all the body surfaces
- provides a barrier function
- arranged in continuous sheets of tightly bound cells
- provide protection against microbial invasion
- regulate movement of substances
- polarised
what are the three specialisations of epithelial tissues
apical, basal and lateral
what is the apical surface of epitherial cells
the upper free surface exposed to the exterior
what is the basal surface of epitherial cells
basement membrane - the lower, attached surface
what are lateral surfaces in epithelial cells
intercellular junctions - can also form folds and processes between neighboring cells to increase the surface area for fluid transport.
what are the three junctions in epithelial tissue
- tight junctions
- desmesomes
- gap junctions
what are tight junctions
these are cells held tightly together by individual groups of tight junction proteins. they prevent water passage by arranging in strands and forming a branched network
what is an example of the purpose of tight junctions in epithelial cells
tight junctions between the epithelial cells lining the bladder prevent urine from leaking out into the extracellular space
what are desmosomes
spot welds between adjacent epithelial cells that allow cells that stretch such as skin and cardiac muscle by remaining unconnected in an unbroken sheet
how do desmosomes remain unconnected in sheets
caherins attached to a structure called the cytoplasmic plaque, which connects to intermediate filaments
what are gap junctions
channels between neighboring cells that allow for the transport of ions, water and ions
how do gap junctions form
six connexons form a donut like structure, which when aligned forms a channel between cells
where are gap junctions important
cardiac muscle
what are connexons
membrane proteins
what are the functions of epithelial tissues
- physical protection
- diffusion
- absorption
- secretion
how can epithelial structure differ
- shape
- number of cell layers
- apical specialisations
what are the different shapes of cells
squamous
cuboidal
columnar
what are the different names for the number of layers of epithelial cells
- simple
- stratified
- pseodostratified
what does simple mean
a single layer of cells
what does stratified mean
multiple
what does pseudostratified mean
one layer of cells has alternating nuclei locations which leads to fake multilayer
what are the different apical specialisations
- microvilli
- cilia
- keratin
what does simple squamous epithelium line
lines surfaces involved in passive diffusion
what are some locations of simple squamous epithelia
alveoli in lungs and capillaries in the endothelium
what does simple cuboidal epithelium line
lines ducts and tubules and controls absorption or secretion
where are simple cuboidal epithelia found
renal tubules and small ducts of salivary glands
which surfaces are simple columnar found on
absorptive surfaces
where are simple columnar epithelia found
in the small intestine
where are microvilli found in the body
small intestine
what does it mean if epithelia is keratised
has keratin ie is hard
what is an ulceration
a break in the continuity of the epithelium
what is a glomerulus
a cluster of capillaries around the end of a kidney tubule
what is the difference between proximal convulated tubules and distal convulated tubules
proximal stains more intensely because they contain more organelles which support all the processes required to facilitate active reabsorption
what is the function of microvilli
increase the surface area of the apical surface and facilitate the function of absorption
where is the pseudostratified epithelium found
only in the respiratory tract
what does the structural arrangement of epithelial tissues depend on
location and function of tissue
what body surfaces do epithelia cover
all of them
what is the epidermis
the outer layer of skin
what is the barrier function of the epithelial tissues
- all substances entering and leaving the body pass through the epithelium
- it acts as a continuous boundary between different environments
how are all epithelia arranged
continuous sheets of tightly bound cells
what is the apical surface
adjacent to or facing the external surface
what is the basal surface
adjacent to or facing the interior surface
what are the lateral surfaces
adhered to each other
what are the features common to all epithelial tissues
structure of continuous sheets of cells that are tightly bound together and are polarised. function of covering and lining surfaces to form a barrier
which epithelial tissues provide physical protection from mechanical abrasian
skin and oral cavity
which epithelial tissues provide diffusion of gases, nutrients, and waste between blood and surrounding tissues
lungs and blood capillaries
which epithelial tissues absorb nutrients
the gastrointestinal tract and renal tubules
which epithelial tissues secrete sweat, mucus, enzymes and hormones
glands and ducts
which shape of epithelial cells can exist in a pseudotratified structure
columnar
what do microvilli do in relation to the apical surface area
increase it
what do cilia regulate
movement of particular matter
what does keratin do
provide a strong protective apical layer
what does ciliated simple columnar function
ciliary action facilitates the transport of ovum from the ovary to the uterus in the female reproductive tract
what is the function of pseudstratified colmumnar ciliated
propels the surface layer of mucus containing trapped particles toward the pharynx in the airways of reproductive tracts
what are goblet cells
modified columnar epithelial cells
what is the function of goblet cells
synthesise and secrete mucus
where are goblet cells located
scattered throughout simple columnar epitheliums like in the respiratory and gastrointestinal tract
what is the function of stratified cuboidal epithelium
secretory
where is stratified cuboidal epithelium found
some secretory ducts and glands
where is stratified columnar found
male urethra and lining some glands
what is the function of stratified columnar cells
secretory and protective
what is the function of stratified squamous epithelia
protect from mechanical abrasion.
what do stratified squamous cells mature from
basal layer from continuously dividing stem cells
what are stratified squamous epithelia shed as
anucleate squames
where are stratified squamous epithelium found
in the oral cavity and on the epidermis
what does keratin do
enhances resistance to physical stress
what do epithelial cells accumulate as they mature
keratin filaments
how is a tough, non living surface layer of cells on the apical layer formed
by the accumulation of keratin in the stratified squamous epithelia
what does transitional epithelium do
allows for expansion and stretch
where is transitional epithelium found
only in the bladder
what is an example of infectious ulceration
herpetic stomatitis
what occurs in oral squamous cell carcinoma
dysplastic epithelial cells proliferate in an uncontrolled manner which destroyes and invades adjacent tissues
