Epithelial Tissue Flashcards
epithelial tissue
-functions
- protection (barrier against disease)
- slows loss of extracellular fluid and nutrients (burn victims lose this function)
- transcellular transport (active movement across cell)
- absorption of nutrients (selective permeability)
- secretion (glands, choroid plexus)
- sensation
- contractility (glandular secretion; myoepithelium)
types of epithelium based on embryology and where are they located?
ectoderm -epidermis of skin mesoderm -endothelial lining of blood vessels endoderm -simple epithelial lining of the GI tract
what separates the epithelium from all of the tissues that it covers
basement membrane
basement membrane
-layers
basal lamina
reticular lamina
basal lamina of basement membrane
- secreted by
- layers
secreted by epithelial tissue
layers
-lamina lucida
-lamina densa
lamina lucida
-composed of…
glycoprotein
-e.g. Laminin
integrins and dystroglycans (bound by laminin)
lamina densa
-composed of…
proteoglycan -Heparan sulfate fine fibrils of collagen type IV -bound by laminin collagen type VII anchoring fibrils
reticular lamina
- secreted by…
- composition
secreted by the fibroblasts of the underlying connective tissue
composition
-collagen fibers types I and III that loop into and bind with anchoring fibrils (collagen type VII)
-anchoring plaques of collagen type IV
reticular lamina
-function
anchors basal lamina to underlying connective tissue by way of the extracellular fiber matrix
epithelium cell type
polyhedral cell (multi-sided)
how are epithelial cells named?
-examples (3)
named by their shape
- squamous (flat)
- cuboidal (centrally located nucleus)
- columnar (apical and basal border with nucleus usually located basally)
epithelium cellular arrangements
simple
stratified
transitional
pseudostratified
simple epithelium
-location and characteristics
single cell layer
endothelial lining of blood vessel, pulmonary alveoli
stratified epithelium
-characteristics and location
more than one layer
may be keratinized (skin) or non-keratinized (moist areas; oral epithelium, vagina, rectum)
transitional
-characteristics
looks like multiple unorganized layers
pseudostratified
-characteristics
looks like more than one layer when they actually aren’t
epithelial cellular connections (6)
terminal bars zonula occludentes (tight junctions) zonula adherentes macula adherentes (desmosomes) gap junctions hemidesmosomes
terminal bars
- location
- functions
location
-attachments surrounding epithelial cells
functions
-provide integrity of the epithelial surface
-provide protection/transport of substances across epithelial membrane
zonula occludentes (tight junctions)
- location
- function
- layers
location
-barrier around entire apical end of cells
functions
-prevents material from taking paracellular route in passing from the lumen into the connective tissue
-aka eliminates intercellular space so material must pass through cell
layers
-occludin
-claudins
zonula adherentes
- location
- components
location
-cell to cell near the apical border (not always complete around the cell)
-basal to tight junction
components
-cadherins: bind to each other in intercellular space
-transmembrane linker proteins with actin molecules
macula adherentes (desmosomes)
- location
- function
- what do they look like
location
-randomly arranged along the lateral cell
disc-shaped plaques that function to attach adjacent cells
gap junctions
-function
couple adjacent cells metabolically and electrically by allowing small molecules and ions to pass between cells
hemidesmosomes
-function/location
attach epithelial cells to underlying basal lamina
cellular specializations of epithelium
microvillus stereocilia cilia glands flagella serous glands -protein-secreting (use rER) mucous glands -goblet cells of the gut -apical end filled with hydrophilic mucin
epithelial cell types and their products
ion transport pinocytosis neurocrine paracrine endocrine myoepithelial cells
ion transport
-what is the function of the cells responsible for this?
magensium dependent Na+/K+ ATPase pump
pushes Na+ against electrochemical gradient
pinocytosis
-what is this process
absorption and excretion of small products or compounds by sequestering the particle in cell membrane
neurocrine
-what is it
neurotransmitter
paracrine
-what is it?
diffusion of compounds into ECF
endocrine
-what is this?
steroids or proteins secreted directly into the vascular system
myoepithelial cells
- what are they?
- function
contain contractile elements (irregular)
line ducts for active excretion of contents of gland (lie between epithelial cell and basal lamina)
regenerative level of epithelial tissue
high
