week 19 structure of epithelium Flashcards
what domains are cells made up of that are polarised (orientated) the same way throughout the epithelial sheet
apical and basolateral
cells sit next to eachother and attach to a thin, fibrous_____
basement membrane
epithelia line the surfaces of ____-
cavities and structures
epithelial sheets lack
blood vessels
epithelial sheets can contain nerves that allow what
neural contribution to sensation, absorption, protection and secretion
in development, epithelia act in conjunction with what other tissue type
mesenchyme
in development, epithelia act in conjunction with mesenchyme (another tissue type) to form what
nearly every organ in the body
if a cell is cuboidal what does this mean
cube shaped
if a cell is columnar what does this mean
rectangular
if a cell is squamous what does this mean
flat
if a cell is simple epithelium what does this mean
single layer
if a cell is stratisfied epithelium what does this mean
several layers
if a cell is pseudo-stratified epithelium what does this mean
one cell, layers of varying heights
if a cell is ciliated what does this mean
primary cilia and motile cilia
if a cell is described with neural connections what does this mean
form sn eural connections
if a cell is described as mucus secreting what does this mean
gobelt cells
for example, if a cell was described as pseudo-stratified ciliated columnar epithelium, what does this mean
cells of varying height but all with single attached to basement membrane
in lung neuroepithelial bodies what are the epithelial functions
chemosensing and regulation of breathing
in kiney nephrons and collecting duct what are the epithelial functions
ion transport]fluid homeostasis
hormone secretion
acid base balance
in the gut mucosa, how is the cell epithelium described (structure)
simple columnar epithelium with goblet cells
what is the epithelial function of the gut mucosa
ion transport
fluid homeostasis
mucus and digestive enzyme secretion
nutrition absorption
how is the epithelium structure of the blood brain barrier described
endothelial interaction with astrocytes
what is the blood brain barrier’s endothelium astrocyte interactions
ion transport
fluid homeostasis
selective hormone signaling
why is polarity crucial for function
gives direction to the transport of ions and nutrients
specialisation of funtion at one end of cell
supprt formation of complex architectural shapes
loss of polarity is key to _____
disease
microvilli gives the apical membrane of the cell increased ______ to increase interactions with external environment
surface area
how mnany layers are there in the epithelial cell junctions
5
what are the 5 layers in the epithelial cell junctions
adherens junction
tight junctions
desmosome junction
gap junction
hemidesmosome junction
A
T
D
G
H
what are cadherins (in adherens junction)
cell adhesion proteins
what are cadherins fundamental for
multicellular (metazoan life)
Ca2+ - dependant homodimerizations between extracellular domains does what
holds cells in contact
carboxy terminus is anchor for what 4 things
p120
alpha
beta
gamma (catenin)
p120 is a what
prototypical catenin isoform
what does p120 do
stabalise adherens junctions and initiates formation of other junction complexes
alpha-catenin forms what
a homodimer
alpha-catenin forms a homodimer that anchors what
actin filaments to the membrane
beta-catenin is released from _____ by _______
E-cadherin by proteolysis
beta-cadherin is releaased from £-cadherin by proteolysis and acts as a what
nuclear signal to stimulate loss of polarity and cell growth
gamma-cadherin (plakoglobin) does what to junction complexes
alters junction complexes
gamma-cadherin alters typ of junction complexes and is common to what
desmosomes
F actin forms supporting ____ structure around what
belt
inner cell membrane
if adherens junction disrupted ____ Catenin move to nucleus and does what
beta
promotes cell growth and loss of polarity (cancer)
Junction complexes stabilise what
cell structure and inhibit cell passage
junction complexes stabilise cell structure and inhibit cell cycle passage by -
sequestering key transcription factors
what type of tight junctions form the apical side of adherens junction and creates an impermeable barrier that blocks intracellular movement of molecules between cells and acts as a fence to separate the apical and basolateral membranes
zona occludens
basic unit of tight junction is what
occluden
homedimerization of occluden extracellular domains forms what
impermeable seal between cells
ransmembrane occluden domains seperate what
apical and basolateral membranes
transmembrane occludens domains seperate apical and basolateral domains, what does this prevent
prevents movement of proteins between these membranes
zona occludens proteins anchor what
cytoskeltal proteins (actin and tubulin) to the tight junction complex
microvilli are supported by actin anchored to where
actin ring
phosphoinositide-3kinase (PI3K) and its inhibter (PTEN) regulate what
phosphoinotiside (Ptdlns) content of apical and basolateral membranes
Par3 recruits PTEN to where
tight junction
PTEN enriches what and where
PIP2 in apical membrane
PI3K localises to where
adherens junctions
PI3K enriches PIP3 to where
Basolateral membrane
____ form loose junctions between cells enabling cell shape to distort without tearing during mechanical stress
desmosomes
desmosomes form what
loose junctions between cells enabling cell shape to distort without tearing due to mechanical stress
where are desmosomes most commonly expressed
cells exposed to stretch and shear (lower airway of lung)
what are desmosomal junctions composed of
cadherin family proteins
desmoglein
desmocollin
desmoglein and desmocollin are anchored in the membrane by what
plakoglobin and plakophillin heterodimers
desmoplakin binds desmin and cytoskeltal protein to where
desmosome junction complex
desmoplakin binds what to proteins to the desmosome junction complex
desmin and cytoskeletal protein
gap junctions are formed from what
hexamers of connexin proteins
gap junctions function as what
channels that connect the cytoplasm of one cell to another
gap junctions are channels that connect the cytoplasm of one cell to another so that they establish what
planar cell polarity (PCP)
how many connexins form a hemi channel
6
extracellular connexin loops link hemi channels between ____
neighbouring cells
channel pore facilitates electric and metabolic coupling between what
cells
channel pore facilitates ____ and _____ coupling between cells
electric and metabolic
what are the major components of the basement membrane (hemidesmosome)
laminin
integrins
collagens
fibronectin
nidogen
perlecan
what is the role of laminin in the hemidesmosome
primary organiser of the BM proteins and froms the lamina densa
what is the role of integrins in the hemidesmosome
expressed on basolateral side of cell and form lamina lucida - binds to lamina
what is the role of collagens and fibronectin in the hemidesmosome
chicken wire like meshwork that gives BM tensile strength
what is the role of nidogen and perlecan in the hemidesmosome
link leminin to collagen and fibronectin
mutations that cause cancer can disrupt the association of PTEN with what and where
Par3 at tight junctions
loss of PIP2/PIP3 signature of apical and basolateral membranes disrupts what
(2)
intracellular trafficking and polarity
degradation of E cadherin releases what
Beta-catenin
degradation of E-cadherin releases Beta-catenin which enters where and increases what
the nucleus and increases cell growth by activating LEF-1/TCF driven expression of cell cycle genes
activation of an autoimmune response which disrupts ________ enhancing pathological paracellular support
tight junction barrier
gluten in diet stimulates _____ secretion from where
zonulin
gut epithelium
gluten in diet stimulates zonulin secretion from gut epithelium which opens
tight junctions
gluten enters the blood stream and promotes what
an autoimmune response which degrades the gut epithelial barrier and further exacerbates immune response
gluten enters the blood stream and promotes an autoimmune response which degrades the gut epithelial barrier and further exacerbates immune response by
augmenting T cell recruitment
in ehlaors danlos what causes the mutation
collagen
in EDS the mutation in collagen genes disrupts epithelial adhesions to the basement membrane resulting in what
hyper flexible joints and loss of cell polarity
