Cell Junctions Flashcards
Cellular junctions
Points of contact between cells
What is the structure/characteristics of tight junctions?
Connections between the plasma membranes of neighboring cells
Bands of tight junction encircle the apical portion of epithelial cells.
Comprised of adjacent plasma membranes, intercellular space, strands of transmembrane proteins
Intercellular (paracellular) space
The space between cells
What is the function of tight junctions?
Prevents diffusion of fluids/solute/waste between cells
Isolates waste inside lumens
Where are tight junctions located?
Epithelial lining of digestive/urinary system and blood vessels
What is the structure/characteristics of adherens junctions?
Consist of adhesion belt, terminal web, and cadherin
Adhesion belt ties to microfilaments in the terminal web
Plaque attaches to actin and cadherin
What is the function of adherens junctions?
Help epithelial surfaces resist separation
Where are adherens junctions located?
Just below tight junctions
What is the structure/characteristics of desmosomes?
Most common type of junction between skin cells.
Fastens adjacent cells into strong sheets.
Plaques attach to keratin and cadherin.
What is the function of desmosomes?
Allows for stretching, bending, twisting, compression.
Attaches muscle cells together.
Where are desmosomes located?
Epithelial tissues subject to stress, such as stratified squamous epithelium (skin)
What is the structure/characteristics of hemidesmosomes?
Essentially one half of a desmosome.
Comprised of plaque, keratin, integrin.
What is the function of hemidesmosomes?
Attach epithelial cells to the basement membrane
Where are hemidesmosomes located?
Basement membrane
What is the structure/characteristics of gap (communicating) junctions?
Communication channels between cells.
Channel proteins (connexons) found in plasma membrane.
