Epithelium Flashcards
epithelium typically sits on a what membrane
basement membrane (basal lamina + reticular lamina) [a non-cellular material which separates the epithelium from an underlying connective tissue
is epithelia vascular or avascular
avascular (no blood supply)
epithelia of skin and oral mucosa derive from what
ectoderm
epithelium lining the respiratory and digestive tracts derives from what
endoderm
epithelium of the urinary tract, as well as the epithelium lining the inside of blood vessels and body cavities derive from what
mesoderm
cell shape of epithelia
squamous (flattened)
cuboidal (height equal to width)
columnar (height greater than width)
epithelia nuclear shape
squamous (flattened)
cubodial (spherical)
colmnar (elliptic)
adjacent connective tissue of epithelia in digestive, respiratory, and urinary tract called what
lamina propria
what is the basal lamina
layer of proteins which separates the epithelium from the connective tissue
only visible w electron microscopy
interface between epithelium and CT often irregular characterized by what and what does this do
papillae
increases the interface surface area
do epithelia cells have polarity
yes
3 domains of epithelial cells
basal domain - part of the cell adjacent to the basal lamina
lateral domain
apical domain - part of cell which forms the free surface of the epithelium
structure of basal lamina
laminins (attach to integrins from cells)
type IV collagen (attaches to laminin network)
entactin (nidogen) and perlecan - attack the laminin network to the type IV collagen
reticular lamina structure and function
part of the connective tissue
type III collagen (reticular fibers) in the connective tissue attach to the basal lamina by anchoring fibrils made of type VII collagen
basement membrane includes what
includes both lamina and reticular lamina
stains well w PAS* stain
visible w light microscopy
what is a zonula occludens and what 2 proteins are important
(tight/occluding junction)
claudin and occluin
what is a zonula adherens, macula adherens and what proteins are important
zonula completely encircles cell
macula attaches at one small point
cadherins - transmembrane glycoproteins, bind to catenin, which links to actin
what protein is important in gap (communicating) junctions
connexons
allow passage of small molecules and ions from one cell to another
examples of tissues w gap junctions and examples of transmitted molecules
cardiac muscle, osteoblasts, and osteocytes of bone
cAMP, cGMP, ions
hemidesmosomes + components
serve as point of attachment of epithelial cells to components of extracellular matrix/basal lamina
integrins replace cadherins, attach the cell to laminins and type IV collagen
microvilli have a what core, structure and function
have an actin core - contractile
-fingerlike projections, found esp in absorptive cells
-increase surface area of apical membrane up to 30 fold
-actin filaments in microvilli attach to actin in terminal web
stereocilia
very long branching microvilli
non-motile
found only in the male reproductive tract and inner ear
cilia and flagella core and what causes movement and structure
axoneme (core) formed of microubules
dynein cuases movement
motile projections from apical membrane
longer and wider than microvilli
simple vs stratified cells
simple - single layer
stratified - 2 or more layers
pseudostratified epithelium
all cells attach to basal lamina
not all cells reach surface
it appears that there are multiple layers of cells but aren’t
urothelium (transitional epithelium)
surface cells change shape as tissue is stretched
urothelium (transitional epithelium)
surface cells change shape as tissue is stretched
(found only in urinary system)
glandular tissues develop from what and grow into what
lining epithelium
grow into underlying connective tissue
exocrine gland parts and mode of secretion and type of secretion
secretory portion and duct
merocrine, apocrine, holocrine
serous, mucous, mixed
myoepithelial cells
special contractile cells help promote movement of secretions in duct system
wrap themselves around secretory portion of the gland and around parts of ducts
endocrine release what and do not use what
release hormones
DO NOT USE DUCTS
paracrine vs autocrine secretion
paracrine - acts on cells in local environment
autocrine - acts on cell which released the factor
what layer of cells act as stem cells to produce new cells
basal layer
