Epithelial Tissue I and II Flashcards
what is epithelial function
- protection
- transcellular transport
- secretion
- absorption
- sensory detection
describe what epithelial cells are made of/their functions
- are ALWAYS avascular –> don’t have blood vessels
- >can’t get too thick as it has to access nearby vessels
what do epithelial cells exhibit?
POLARITY
attached basally to a basement membrane
apical side faces into lumen/outside world
lateral domain borders neighboring cells
basal domain
borders on basement membrane, related to underlying connective tissue
name an apical specialization
microvilli
what do microvilli do?
they extend into the lumen to increase surface area for absorption
where are microvilli found?
places like the intestines or the kidney tubules
what is the make up of microvilli?
they have an actin core
actin is STIFF
what is the glycocalyx and what does it do?
is: carb chains linked to membrane proteins or lipids
does: associated with microvilli and aids absorption
what are cilia?
mobile, hair like structures that extend from dark basal bodies
they always move and tend to do so in the same direction
what core do cilia have?
microtubules
how do the microtubules change within a cilia?
basal bodies: near the base, 9 triplet formation
cilium proper: near the top, 9 + 2 arrangement
what are the lateral domain functions
1) form a selective barrier
2) adherence
3) communication
what are lateral interdigitations and what do they do?
they are infoldings between cells
are prominent in cells engaged in fluid transport —> ex: intestines
they increase lateral surface area
what is the junctional complex made of?
zonula occludens (tight junction) —-> more apical
zonula adherens (intermediate junction)
macula adherens (desmosome) —-> still apical but less so
what is the zonula occludens function?
form a protective barrier between epithelial cells
separates the luminal space from the intercellular space and the CT compartment
is the first line of defense
essentially the police
has intermittent contact and separations of lateral plasma membranes of adjacent epithelial cells
what is the zonula adherens function
cell to cell adhesion as cells do not contact each other
how do cells connect?
integral membrane proteins
the cells themselves do not touch - are instead connected by a bridge essentially
what is the macula adherens function?
cell to cell adhesion
what are macula adherens made up of?
attachment plaques (gives stability), intermediate filaments, linking proteins
what are gap junctions?
specialized lateral domain
what do gap junctions do?
exchange or signaling between adjacent cells
found in tissues that accomplish coordinated functions —> ex: cardiac muscle, neurons
what is the structure of a gap junction?
one cell membrane that has connexons that can be open or closed
connexons connect to other connexons to pass things between cells
what are lateral domains made up of?
the junctional complex + gap junctions
name a basal domain specialization
cell to ECM adhesion
what are hemidesmosomes and what are they associated with?
1/2 a desmosome and help the epithelial cell attach to the basal lamina
are associated with attachment plaques and intermediate filaments
describe focal adhesions/what they are associated with
associated with actin filaments
important for mechanoreception and proprioception
how are covering epithelium classified?
by the number of cell layers (either simple or stratified)
shape of cell closest to lumen/outside world
name the types of simple classifications
1) squamous - flat
2) cubodial - square/cubes
3) columnar - taller
name the 2 types of stratified epithelium and how they are specifically named
non-keratinized (very tough) and keratinized (toughest)
named for shape of cells in the apical layer
what is the pseudostratified columnar epithelium?
SIMPLE EPITHELIUM
1 cell layer thick
all cells “touch” the basement membrane but don’t all reach the lumen
what is the transitional epithelium?
STRATIFIED
unique rounded surface cells, distensible property (=urothelium)
ONLY FOUND IN URINARY BLADDER
round = no urine, distended = lots of urine
name the 2 types of gland tissue and what they do
1) parenchyma: epithelial cells —> working cells
2) stroma: CT —> supporting tissue
what do endocrine glands do
secrete hormones into blood or lymphatic vessels located in CT
what do exocrine glands do
secrete into ducts
describe endocrine glands
-small secretory granules located in basal cytoplasm
are polarized TOWARD the basement membrane —> REVERSE POLARITY
secretion can be constitutive or regulated
how are exocrine glands classified?
- structure (branching of ducts): simple or compound
- can also be under shape of secretory unit: tubular, acinar (berry), etc
- type of secretion: serous (watery) or mucous
describe serous-secreting compound glands
- pyramidal-shaped cells
- basally located, round nuclei
- basophilic basal cytoplasm
- apical cytoplasm: lighter stained, secretory granules
what organelle is abundant in the basal portion of the cell?
rER
where is the golgi complex located?
supranuclear
where are the secretory granules located?
apical cytoplasm (toward lumen)
describe mucous-secreting glands
- goblet cells: not in a gland
- secretes mucins (hydrophilic glycoproteins)
TEM: rER in basal portion of cell, supranuclear golgi complex, secretory granules in apical region
STAINING: pale apical cytoplasm, darkly stained nuclei basally
