3: Epithelial Border Modifications & Glands Flashcards
Epithelial junctions
most part of the junctional complex located on the lateral border of epithelial cells
Tight junctions
outer membrane of neighboring cells is fused, sealing the intercellular space from the lumen
3 types of cytoskeletal linked junctions
- adherent junction
- desosomes
- hemidesmosomes
Adherent junction
forms an adhesion belt near apical surface beneath tight junction, membranes not totally fused but plasma proteins (anchored by actin filaments) interact with each other
Cadherins
the plasma proteins in adherent junctions
Terminal bar
tight junction and adherent junction
Desmosomes
similar to adherent junction but not located near the lateral luminal surface and have extracellular filaments which further anchor the membranes together
What cell types are desmosomes common in?
stratified squamous
Hemidesmosome
half a desmosome used to anchor the cell to the basal lamina
Gap juctions
proteins form a central pore between membranes to allow of electrical and chemical communication
What are microvilli composed of?
actin filaments
Microvilli purpose
increase surface area in absorptive epithelia
Striated border
microvilli in the gut
Brush border
microvilli in renal tubules
Stereocilia
branched microvilli found in the epididymis
What cell type are microvilli commonly found on?
simple columnar
What are cilia composed of?
microtubules
T/F: Cilia use ATP
T
What tracts are cilia commonly found in?
respiratory and reproductive
What cell types are cilia usually found on?
pseudostratified columnar
Glands
specialized epithelial cells modified into secretory structures that produce a variety of products for extracellular use
Unicellular glands
single secretory cell
What is the most common unicellular gland?
goblet cells
Where are goblet cells commonly found?
respiratory and GI tracts
What do goblet cells secrete?
mucopolysaccharides
Multicellular glands
an accumulation of specialized secretory cells
Endocrine glands
ductless glands that have lost their original embryonic connections to the epithelial surface form which they originated
T/F: Endocrine glands have junctions and polarity
T
Exocrine glands
maintain a communication (duct) within the surface epithelium
Simple exocrine glands
ducts do not branch
Adenomeres
secretory end pieces of simple exocrine glands
How are simple exocrine glands classified?
tubular, coiled, or acinar
Where are simple exocrine glands usually found?
within an organ
Compound exocrine glands
have elaborate branching duct systems
How are compound exocrine glands classified?
tubular, acinar, or tubuloalveolar
Where are compound exocrine glands found?
they are discrete anatomic structures or organs themselves
4 types of secretion
- serous
- mucous
- mixed
- lipid
Serous secretion
water secretion with rounded nuclei near base of the cell and secretory granules at the apex
Mucous secretion
viscous secretion of polysaccharides where the nuclei are flattened near the base and the cytoplasm is pale-stained
Mixed secretion
a combination of both serous and mucous secretory units found in the same gland
Lipid secretion
lipid secretion such as milk, sebum, cerumen
What is the most common mode of secretion?
merocrine
Merocrine
loss of secretory product only by exocytosis
