Download Epi-modif, glands

Today: Epithelial Tissue
Modifications of epithelium
(Classification of epithelial membranes)
Epithelial Glands
Stratified squamous (nonkeratinized) epithelium
-location, function
Stratified squamous (keratinized) epithelium
-keratin in cells
-location, function
Stratified Cuboidal Epithelium
Stratified Columnar Epithelium
Transitional Epithelium
Pseudostratified Columnar Epithelium
-ciliated
What epithelia have in common:
-polarity.
The luminal and serosal surfaces
Apical and basolateral surfaces
-cell surface specializations
eg.
-apical domain/basolateral domain
Some epithelial cells have:
Microvilli
-striated border, brush border, stereocillia
-actin filaments cross linked and attached to
apex by villin
-terminal web has actin, spectrin, and intermediate
filaments.
Glands:
Parenchyma - glands and ducts
Stroma - connective tissue (CT) supporting
the parenchyma
Exocrine glands
-secretory portion and duct portion
Endocrine glands
Multicellular Exocrine Glands
-Simple
*tubular
*branched tubular
*coiled tubular
*acinar
*branched acinar
-Compound
*tubular
*acinar
*tubular acinar
Know glands by the type of secretion:
-mucous
-serous
-mixed glands
-serous demilunes in salivary glands
Know glands by the way the secretion is released:
-Merocrine, by conventional exocytosis
-Apocrine, a portion of the cell breaks off (lactation)
-Holocrine, entire cell is released (sebaceous gland)
Unicellular exocrine glands
-goblet cells
-
Junctional Complex:
Terminal bars
-Occluding junctions
-Adhering junctions
Occluding Junction:
-aka zonua occludens, tight junction
-transmembrane junctional proteins, like a zipper
-leakiness of the junction depends on the number
of zipper rows
-the branching rows of transmembrane junctional
proteins can be seen by freeze fracture TEM
-membrane is pentalamellar by thin section TEM
Adhering Junctions:
zonula adherens - encircle cells
macula adherens - desmosome - like spot welds
Zonula Adherens:
-intercellular space is 15 - 20 nm
This space contains cadherins - calcium dependent
transmembrane linker proteins.
-on the intracellular side, proteins, vinculin and
a-actinin bind the mb to actin web
Macula adherens (desmosome):
-intercellular space is 30 nm
-attachment plaque on the intracellular side of
the mb made of desmoplakin.
-cytokeratin (intermediate filaments, 10 nm) attach
to the plaque.
-intercellular space has desmoglein and cadherins
Hemidesmosomes:
Anchor epithelial cells to the basal lamina
-attachment plaque with desmoplakin
-IF, keratin tonofilaments don’t enter the plaque
-trans-membrane linker proteins are integrins
-these bind to laminin & type IV collagen of basal lamina
Gap Junctions are communicating junctions
-intercellular space is 2 - 3 nm
-adjoining windows between cells
-windows are connexons, made of protein connexin
-gap junctions pass ions, small molecules (cAMP)
-opening and closing of the gaps can be regulated