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Cell junctions
description, function and location of cell junctions (A&P text book, Tortora's 12th edition)
27
Anatomy
Undergraduate 1
03/07/2010

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Term
what are cell junctions
Definition
Cell junction - contact point between plasma membranes of tissue cells
Term
main role of TIGHT junctions
Definition
prevents leakage& passage of materials between cells
Term
how are tight junctions formed?
Definition
plasma membranes of two cells are fused with a strip of proteins
Term
two main locations (tissue + organ)where cells are connected via tight junctions
Definition
1. epithelium of bladder (prevents urine leakage)
2. epithelium of intestine & stomach (prevents food leakage)
Term
true/false: in tight junctions the two cells are connected via plaque proteins
Definition
FALSE: tight junctions DO NOT INVOLVE PLAQUE PROTEINS!
Term
type of cell junction whose main role is to hold epithelial cells together
Definition
Adherens junctions
Term
role of Adherens junctions
Definition
holds EPITHELIAL cells together & help them resist separation during CONTRACTILE activities (passage of foods through intestine)
Term
3-part structure of Adherens junctions
Definition
1. PLAQUE (dense layer of protein inside cell membrane)
2. transmembrane glycoproteins (CADHERINS): cross the plaques of the two connected cells
3. microfilaments of ACTIN extend through cytoplasm
Term
what are Cadherins
Definition
Cadherins = transmembrane glycoproteins that cross the plaques of two adjacent cells in ADHERENS junctions
Term
in which cell junctions are CADHERINS found
Definition
cadherins are found in Adherens junctions & Desmosomes
Term
cell junction that resists cell separation and disruption during TENSION & provide cellular support for CARDIAC muscle
Definition
desmosome
Term
2 functions of desmosomes
Definition
1. resist cell separation and disruption during TENSION
2. cellular support of cardiac muscle
Term
3-part structure of desmosomes
Definition
1. Plaque
2. transmembrane glycoproteins (cadherins)
3. Intermediate filaments (Keratin)
Term
from structural perspective, how are Adherens and Desmosome junctions different
Definition
Adherens have microfilaments made of actin.
Desmosomes have intermediate filaments made of keratin
Term
two locations of desmosomes
Definition
1. epidermis
2. cardiac muscle cells
Term
role of Hemidesmosomes? What makes them different form other cell junctions?
Definition
Hemidesmosomes anchor cells to the basement membrane!!!!
Hemidesmosomes DO NOT link adjacent cells!
Term
type of cell junction that doesn't involve the connection of adjacent cells
Definition
Hemidesmosomes
Term
structure of hemidesmosomes
Definition
1. usually NO Plaque
2. Glycoproteins = INTEGRINS
Term
what are the glycoproteins found in hemidesmosomes?
Definition
INTEGRINS
Term
where are hemidesmosomes widely distributed?
Definition
within EPITHELIA (which has basement membrane)
Term
what are GAP junctions
Definition
Gap junctions= tiny intercellular gap between the plasma membranes
Term
which cell junction makes the small space between two cells
Definition
gap junctions
Term
what is specific to the structure of gap junctions
Definition
gap junctions are crossed by CONNEXONS= protein channels between the two plasma membranes, filled with fluid
Term
in which cell junctions are connexons found?
Definition
gap junctions
Term
role of connexons in gap junctions
Definition
throught connexons, cells exchange ions and small molecules
Term
true/false: in gap junctions the two cells are connected through plaque
Definition
FALSE: There is NO PLAQUE in gap junctions!!!
Term
3 locations of gap junctions
Definition
1. involuntary muscle (cardiac & smooth)
2. osteocytes
3. epithelia of gut
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