Lecture 8 Flashcards
What are the general features of epithelium?
- Avascular
- covers external body surfaces
- lines internal closed cavities
- lines body tubes
- forms secretory portion of ducts of glands (parenchyma)
- specialized cells function as receptors for special senses.
What are the three characteristics of epithelium
- the cells are closely apposed and adhere to each other
- exhibit functional and morphological polarity
- the basal surface is attached to an underlying basement membrane
What are the three surface domains of epithelial?
- free space / apical domain
- lateral domain
- basal domain
What are the junctional complexes of the lateral domain?
- Occluding junction
- anchoring junction
- communicating junction
Example of an occluding junction?
tight junction or zonula occludens
Example of anchoring junctions?
- adhering junctions (zona adherens)
2. Desmosomes (macula adherens)
Explain zona occludens?
Occluding junctional complex (cell to cell)
It is a tight junction
function:
- localized sealing of the PM of adjacent cells
What transmembrane proteins can be found in the zona occludens?
caludins- Forms backbone of ZO and forms/regulates aqueous channels
occludins- maintains barrier between apical and lateral cell surface
JAM- mediates interactions between endothelial cells and monocyte adhesions
ZO-1 = important link in transduction of signals
ZO-2- required in epidermal growth factor-receptor signaling
ZO-3 = Interacts with ZO-1. occludin, and actin
What domain separates the luminal space from the intercellular space and connective tissue?
zonula occludens
What domain establishes the functional domains: apical and basolateral?
zonula occludens
Explain the zonula adherens?
anchoring junctional complex (cell to cell)
lateral adhesion between cells
it is a continuous band that surrounds the entire cell. (beneath the tight junction)
What protein is found in the zonula adherens?
E-cadherin (calcium dependent)
helps to attach adjacent cells
interacts with actin
Explain the macula adherens?
anchoring junctional complex
macula adherens = desmosome
lateral, localized, spot adhesion
focal dense spots (macula)
Where is the macula adherens found?
Found below the zonula adherens
What proteins are found in the macula adherens?
Transmembrane protein:
desmocollin
desmoglein
(cadherin family, Ca dependent)
Intracellular plaque:
plakoglobins
desmoplakins
interacts with intermediate filaments
What are the functions of gap junctions
communicating junctional complex
help coordinate activity of adjacent cells
Where are gap junctions found?
epithelium
smooth and cardiac muscle
nerve tissue