Epithelial Tissue Flashcards
epithelial tissue
how do cells look like?
space between cells?
surfaces?
crowded cells
small spaces
upper surface- free
basal - rests on membrane
epithelial tissue
blood vessels and nerve cells
blood vessels cannot penetrate but nerves can
so, it is avascular (no blood cells)
how does epithelial tissue get its nutrition
it has..
by connective tissue
high power of regeneration/renewal
origin of epithelial tissue
all 3 layers
ectodermal
mesodermal
endodermal
epithelial tissue is classified into and function of each
surface epithelium - covers
glandular epithelium - for secretion
neuro epithelium - act as receptor
myo epithelium - contractile function
surface epithelium types
simple- 1 layer
stratified - 1+ layer
simple squamous
formed of + nuclei
functions
formed of 1 layer of flat cells with flat nuclei
function:
provide smooth surface for easy movement
thin membrane for gas exchange
sites of simple squamous
- endothelium (wall of blood vessels)
- lines of lungs (pneumocytes)
- lines serous membranes (3P- pleura, pericardium, peritoneum) - mesothelium
4 lines bowman’s capsule of kidney
simple cubical epithelium
formation + nuclei
function
sites
1 layer of cube like cells with central rounded nuclei function: secretion and reabsorption sites: small ducts like glands thyroid follicles colvoluted tubules of kidney
simple columnar epithelium
formation + nuclei
functions
sites
formed of 1 layer of tall columnar cells with basal oval nuclei functions: secretion and absorption sites: stomach intestine pancreatic duct, bile duct, gall bladder goblet cells
simple columnar ciliated epithelium
formation + nuclei
functions
sites
1 layer of tall columnar cells with basal oval nuclei with cilia
functions:
transport fluids or particles in 1 direction
sites:
1. lower part of respiratory tract (lungs)
2. female genital system
psedostratified columnar epithelium
types
1 layer but looks like 2 and nuclei on different levels
1. pseudostratified columnar non ciliated
site: male genital system
2. pseudostratified columnar ciliated with motile cilia and goblet cells
site: upper respiratory tract (nose, bronchi, trachea)
3. pseudostratified columnar ciliated with non motile cilia (stereocilia)
not true cilia, long microvilli
site: epididymis
function of stratified epithelium
protection
stratified squamous epithelium vs transitional epithelium
# of layers
basement membrane
stratified squamous epithelium - 5-30 layers
clear and wavy membrane
transitional epithelium - 6-8 layers in empty bladder
3-4 in full bladder
non clear, non wavy
stratified squamous epithelium vs transitional epithelium - basal cell layer
stratified squamous epithelium - columnar cells w/ basal oval nuclei (others originate from this layer)
transitional epithelium - cube cells with central round nuclei
stratified squamous epithelium - intermediate layers
polyhedral cells with central rounded nuclei
cells are joined by desmosome
cells become smaller toward surface
transitional epithelium - intermediate layer
polyhyderal cells with central rounded nuclei
in full bladder- cells slide past eachother -> decrease epithelium thickness
superficial layer - stratified squamous vs transitional
transitional - connected by
covered by
stratified squamous - flat cells with flat nuclei
transitional - dome shaped with central round nuclei and connected by junctional complex
empty bladder- flat cells
covered by rigid plaques
stratified squamous sites
keratinized- dead, dry places
non keratinized - wet, living, opening on skin
transitional epithelium sites
lines of urinary tract (urothelium)
stratified squamous epithelium vs transitional epithelium - function
squamous - protection
transitional - destinsibility and protection against urine
layers of stratified
top is variable
middle is always polyhydral
bottom is always columnar shaped
stratified cubical epithelium
ex
rare of two layers in ducts of sweat glands
stratified columnar epithelium
similar to squamous but superficial cells are columnar
types:
stratified columnar ciliated: in fetal oesophagus
stratified columnar non ciliated : in recto and junction, large ducts or glands, male urethra
neuro epithelium
acts as
consists of
sites and functions
acts as receptor and stimuli for sensation
consists of sensory and supporting cells
sites & functions:
taste buds
organ of corti - ear for hearing
macula utriculi and sacuule - ear for balance
crista ampullaris - ear
myo epithelium
site in between
how do they work
modified to contract
in between base of secretory cells and basement membrane
squeeze secretory cells to discharge into ducts
apical specializations
come from above
- microvilli
- celia
- flagella
microvilli
what type of filaments does it have
function
finger like
has actin filaments which helps its shape and length
function: increase surface area for absorption
stereocilia
filaments?
function?
non motile solid cilia not true cilia, long microvilli hair like has actin filaments function: help absorption in male genital system
cilia
formed of
hair like
formed of microtubules
flagella
single long cilia that from tail of sperm for movement
glandular epithelium
act as gland for secretion
glandular epithelium are classified to
exocrine gland
endocrine gland
mixed gland
glandular epithelium classification - exocrine
formed of 2 portions
secretory - forms secretion
excretory - carries secretion to outside gland
glandular epithelium classification - endocrine
ductless
formed of secretory but no duct system, their secretion is carried to blood
glandular epithelium classification - mixed
formed of exocrine part - ducts
endocrine part - no ducts
classification of exocrine glands - according to # oc cells
unilocular - one cell , not popular
multilocular - 1+ cells
classification of exocrine glands - according to type of secretion
watery secretion
serous secretion : watery but contain enzymes
mucus secretion
mucoserous secretion
classification of exocrine glands - according to mode of secretion
- merocrine ; most common, secretion goes outside cell by exocytosis
- apocrine ; released out of apex of cell
- holocrine ; secretion accumulates then cell bursts and the cell is lost with secretion
classification of exocrine glands - according to branching of duct
simple - single non branching duct and secretory part
compound - has branching duct like tree
classification of exocrine glands - according to shape of secretory part
tubulor - tube
alveolar (acinar) - rounded
tubuloalveolar - flask shape
lateral (side) specializations - cell junctions - tight or occluding junction
Zonula Occludens
2 cell membranes fuse at certain points to restrict passage of substances between adjacent cells
lateral (side) specializations - cell junctions - adherens junction
function
zonula adherens
two cell membranes seperates by wide intercellular space
encircles cell like belt
function to provide adhesion between epithelial cells
intercellular space and cytoplasm in zonula adherens
location
connecteted by
intercellular - transmembrane proteins on each side connected by Ca ions
cytoplasm - protein bind transmembrane protein to actin filaments (cytoskeleton)
macula adherens
desmosomes
strongest type of junction that provide firm adhersion among cells
mostly in stratified squamous epithelium cells
gap junction
nexus
two cells separated by narrow cap but connected by channels
each channel = 2 connexons = 6 subunits
functions of gap junction
permit exchange of ions and impulses
hemidesmosomes
basal
1/2 desmosome
function: fix epithelium to membrane and connective tissue
basement membrane
stain and types
PAS- red
Ag- Silver
types:
basal lamina - epithelial component - has collagen type 4
reticular - ct component - collagen type 3
function of basement membrane
supports epithelium and fix it to CT by collagen type 7
control passage of nutrients and ions
basal infoldings
basal surface shows invaginations to increase surface area
has mitochondria
occurs in ion transporting cells
