Histology: epithelial tissue Flashcards
simple cuboidal
function? where are they found?
one layer of cube shaped cells
ex of locations: nephrons of kidney, glands and ducts
lines structure where secretion and/or absorption takes place.
actively involved in transporting substances in or out of a lumen, or into or out of the extracellular environment.
simple squamous. what is it? where is it located?
one layer of flat cells
lining of blood & lymph vessels, and heart
thin thickness allows O2 to diffuse to underlying tissue and nutrients too
some cells can crawl between the spaces that exist
simple columnar: where are they found? function?
one layer of column shaped cells
lining of most digestive track, lining of gallbladder, glands, lining of small bronchi, lining of uterine tubes,
absorption and secretion
similar to cuboidal, but forms an even thicker barrier
stratified squamous
2 or more layers of cells where the top layer has flattened cells.
ex of location: skin, lining of oral cavity and esophagus, lining of vagina
protects underlying tissue
replaced rapidly
pseudostratified epithelium: where is it found?
single layer of cells attached to the same basement membrane, cells of varying heights become superimposed over each other.
found in the upper respiratory tract
transitional epithelium
unique to the urinary bladder
appears different depending on if organ is empty or full
full: represents squamous
relaxed: stratified and cuboidal, scalloped appearance
zonula adherens: what are the three components? are they near the apical or basolateral surface?
links contiguous epithelial cells via cadherins
anchor proteins
actin filaments
tend to be close to the apical surface?
Desmosome
cadherins
anchor proteins
keratin filaments INSTEAD of actin
keratin is MUCH STRONGER than actin = desmosomes are much stronger than keratin
positioned near zonula adherens but towards the basolateral surface of the cell.
tight junctions
extracellular domains of transmembrane proteins on the lateral surfaces of adjacent cells interlock with the help of calcium.
maintains polarity of cell
can block passage of luminal content between cells
cytoskeleton of cell does NOT contribute to tight junctions
gap junctions: what forms them? what does it do?
formed by transmembrane proteins called connexins. many protein chains form a connexon
creates a channel where cytoplasm and its water soluble contents can flow between cells
what is the basement membrane? what kind of tissue is it? is it vascular? do nerves penetrate? what is its function?
thin, fibrous connective tissue layer between the epithelium and underlying supporting tissue.
AVASCULAR-blood vessels do not penetrate BM but allows it to transudate (fluid leaked out serves the cells of the overlying epithelium)
nerves penetrate the BM
controls epithelial growth, impends epithelium from growing downwards.
is the basement membrane cellular? what is it made of?
what are the primary components?
it is not cellular. it is produced by TWO types of cells:
1) epithelial cells supported by the BM
2) fibroblasts of the underlying supportive tissue
the primary components are:
1) type IV collagen** (forms flat sheets)**
2) GAG called heparin sulphate
3) ground substance (GAG and proteoglycans including: fibronectin, laminin, and entactin)
what is the most common glycoprotein in the BM?
what does it do?
laminin.
laminin attaches to 1) other components of the BM and 2) transmembrane proteins in the epithelial cells called integrins
integrins transmit information about external stress to the epithelial cell nucleus. important in responding and recovering from injury.
what links the epithelial cells to the basement membrane?
hemidesmosomes link epithelial cells to the basement membrane
they are similar to desmosomes
the components are:
laminin (in the BM)
anchor proteins
integrins in the epithelial cells that are attached to the keratin of the cytoskeleton of the epithelial cell
exocrine glands
secrete products into ducts, and ultimately lead to the exterior of the body.
acinar glands: resemble bunches of grapes.
