Lectures 4-5: Epithelial Tissue Flashcards
functions of epithelial tissue (5)
-sensory detection
-absorption
-secretion
-transport
-protection
epithelial structure: rules (4)
-avascular
-covers body surfaces
-lines internal, closed body cavities and tubes (like blood vessels)
-constitutes glands
how do epithelial cells exhibit polarity
-cells closely positioned and attached to one another
-attached basally to basement membrane
-face into a lumen or to outside world
3 domains of epithelial cells
-apical
-lateral
-basal
apical domain definition
borders on the lumen
lateral domain definition
borders on neighboring cells
basal domain definition
borders on basement membrane, related to underlying connective tissue
microvilli function
extend into lumen to increase surface area for absorption
where are microvilli found
intenstines and kidney tubules
microvilli aka
brush border or striated border
microvilli structure (4)
-villin at top
-actin core
-terminal web
-intermediate filaments
function of glycocalyx
increase surface area for absorption
glycocalyx structure
carbohydrate chains linked to membrane proteins or lipids
cilia definition
mobile, hair like structures extending from dark basal bodies
is glycocalyx associated with cilia? why
no, no absorption
how do cilia move and why
all in same direction for a specific purpose
how is core of cilia different from microvilli
cilia have core of microtubules
microtubules arrangement
9 + 2 (9 peripheral doublets and 2 central singlets )
function of basal bodies
anchor cilia
arrangement of basal bodies (2 different ways)
-9 triplets (9 groups of 3)
-turn into 9+2 as they extend into cilium
3 functions of lateral domain
-form selective barrier for things to go through or between
-adherence
-communication between cells
absorption takes place in which domains
apical mostly, some in lateral
3 parts of junctional complex: epithelial cells (list both names)
-zonula occludens (tight junction)
-zonula adherens (intermediate junction)
-macula adherens (desmosome/spot junction)
list junctions from most apical to basal
-zonula occludens is most apical
-desmosome is most basal
main functions of zonula occuldens/tight junction (2)
-form protective barrier between epithelial cells (first line of defense)
-separate luminal space from intercellular space and connective tissue
how can the tight junction change
can be really tight or leaky depending on tissue type (would want it to be very tight in blood brain barrier to prevent substances from entering)
zonula occludens: how does it work
-plasma membranes of 2 neighboring epithelial cells are joined together intermittently
-will separate and come back together for contact before separating again
leakiness of zonula occludens is related to what
number of ridges and grooves
after zonula occludens, do cells every come back together
no
zonula adherens main function
cell to cell adhesion, but cells do not contact each other directly
2 components found in zonula adherens
-actin
-intermediate filaments
what joins cell cytoskeletons together: epithelial cells
linking proteins
main function of desmosomes
cell to cell adhesion, but cells don’t touch
macula adherens/desmosome structure
-attachment plaques
-intermediate filaments
-linking proteins
attachment plaques function
-associate with intermediate filaments to provide more structure and stability for desmosome
what are spot welds in desmosome/macula adherens
small dot of adhesion attached to intermediate filaments
are gap junctions part of the junctional complex
no
gap junction definition
-specialized lateral domain
main function of gap junction
exchange or signaling between adjacent cells
how do gap junctions work
-2 cells approach each other and get very close (2 nm wide gap)
-allows for direct passage of signaling molecules from one cell to another
where are gap junctions found (what kind of tissues)
-tissues that accomplish coordinated functions
-cardiac muscle, neurons, rods and cones
gap junction structure (2)
-2 cell membranes
-communicating connexons
connexons can be ______ or __________
open, closed
how connexons work
connexons come together between 2 cell membranes
-substances pass through connexons
what substances can’t enter the connexon
substances in intracellular space
can substances in the connexon can’t leak into the intracellular space
no
what is the lateral domain composed of
junctional complex and gap junctions
which way does the basal domain face
towards basement membrane
f
what is basement membrane stained with
periodic acid schiff
2 components of basement membrane
-basal lamina
-reticular lamina
2 ways epithelial cell attaches to basal lamina
-hemidesmosomes
-focal adhesions
hemidesmosome means
1/2 desmosome
hemidesmosomes are associated with
attachment plaques and intermediate filaments
function of attachment plaque
attach cell to basal lamina
attachment plaques are associated directly with
intermediate filaments
focal adhesions are important for
mechanoreception and propioception
focal adhesions are associated with
actin filaments
classification of covering epithelium: 2 main ways (general)
-number of cell layers
-shape of cell closest to lumen or outside world (apical)
in terms of number of cell layers, epithelial cells can be __________ or ______________
simple, stratified
simple epithelium definition
-one layer
-every single cell touches the basement membrane
3 epithelial cell shapes
-squamous
-cuboidal
-columna
stratified epithelium definition
more than 1 layer
how are stratified epithelium named
for shape of cells in apical layer
2 types of stratified epithelium
-keratinized
-non keratinized
keratinized stratified epithelium
-not alive, no nuclei
-toughest
-makes up most skin
pseudostratified epithelium are always what shape
columnar
is pseudostratified epithelium simple or stratified
simple
feature of simple epithelium
basal cells which don’t go up all the way to lumen but still touch basement membrane
transitional epithelium is a subtype of which kind of epithelium
stratified
transitional epithelium unique feature
rounded surface cells gives epithelial cells distensible property
transitional epithelium is only found in which organ
urinary bladder
transitional epithelium aka
urothelium
apical cells of transitional epithelium are rounded when
no urine is in bladder
glands are created partially from
epithelial tissue
2 types of subtissue that create glands
-parenchyma
-stroma
parenchyma: origination and function
-created from epithelial cells
-working cells
-secrete mucous, sweat, etc
stroma: origination and functions
-created from connective tissue
-supporting tissue
2 kinds of glands: general
endocrine and exocrine
endocrine glands: function
secrete hormones into blood or lymphatic vessels located in connective tissue
exocrine glands function
secrete into ducts
where does secretion take place normally (apical or basal)
apical
endocrine glands exhibit what unique features (2)
-ductless, no lumen
-polarized towards basement membrane instead of apical surface (reverse polarity)
where do endocrine secretions go
into blood vessels (capillaries) in stroma
2 types of endocrine secretion
-regulated
-constitutive
constitutive endocrine secretion
endocrine cells that secrete steroid hormones
in endocrine cells, which organelle is likely in abundance
smooth ER
regulated endocrine secretion
secretion is regulated by stimulus
2 ways exocrine glands are classified
-structure
-type of secretion
structure of exocrine glands can be divided into 2 parts:
-branching of ducts
-shape of secretory unit
2 types of branching: exocrine glands
-simple (little to no branching)
-compound (multiple layers)
2 shapes of secretory unit: exocrine glands
-tubular
-acinar (berry shaped)
2 types of secretion: exocrine glands
-serous (watery)
-mucous
serous secreting compound glands: structure/appearance
-cells are apical to duct
-nucleus is always basal
-secretion is apical
-pyramidal shape
under light EM, are mucous cells or serous cells darker
serous cells
what organelle is abundant in basal portion of cell of serous secreting glands
rough ER
where is golgi complex located in serous secreting compound glands
above nucleus, near secretory granules
where are secretory vesicles located in cell of serous secreting glands
apical cytoplasm near lumen
how are mucous secreting glands classified as epithelium
pseudostratified columnar epithelium
example of mucous secreting gland
goblet cells
what do goblet cells secrete specifically
mucins (hydrophilic glycoproteins)
organelles present and orientation difference between serous and mucous cells?
no
how to tell serous and mucous cells apart
-mucous: lumen tend to be larger, nuclei look compressed because mucous is heavy
