Module 6 - Interactions between cells in multicellular systems Flashcards
Four major tissue types
Muscle
Nervous
Connective
Epithelia
The gut: the tissues comprising it and its significant features
Epithelia at the top (absorbing food) and bottom, connective tissue connecting epithelia and smooth muscle (for peristalsis) with nerve cells connecting as well
- Low ECM
- Intermediate filaments and cell-cell junctions provide strength
The skin: the tissues comprising it and its significant features
Epithelia at the top, connective tissue connecting epithelia and muscle with nerve cells connecting as well
- Low ECM
- Intermediate filaments and cell-cell junctions provide strength
Types of epithelia
Simple squamous (flat)
Simple cuboidal (cuboidal)
Simple columnar (columnal)
Non-keratinised stratified squamous
Keratinised stratified squamous
Pseudostratified columnar with goblet cells
Tight junction: what are they and what other key features do they have?
Seals neighbouring cells together in an epithelial sheet to prevent leakage of extracellular molecules between them - allowing functional polarisation
- Found in vertebrates
- Formed from occludin and claudin proteins
- Allow lipids in the plasma membrane to diffuse freely, but NOT membrane proteins
- Protein composition of the apical and basal membranes can be different
Gap junction
Connexon channels (2-4nm) between adjacent cells allowing ions and small molecules (<1000 daltons) to pass through
Adheres junction
Two actin bundles joined together between neighbouring cells using cadherins
- Forms adhesion belts (continuous bands of adheres junctions)
- Can be contractile when myosin II interacts
Desmosomes
Intermediate filament bonding between neighbouring cells using cadherins
- Strong tensile strength
- Abundant in heart muscle and tough, exposed epithelia
Hemidesmosomes
Intermediate filaments anchored to the basal lamina
Integrins used
Types of cell connections between animal cells
Gap junctions
Tight junctions
Adheres junctions
Desmosomes
Hemidesmosomes
Plasmodesmata
Gap junction equivalent in plants
The only type of cell connections within plants
Transcytosis
Polarised transport of proteins from one end of the epithelia to the other
Cadherins
Transmembrane proteins in the plasma membrane which bind to an identical cadherin in the next cell
Interaction needs calcium (Ca²⁺)
Integrins
Trans-membrane proteins in the membrane that link the ECM to the cell’s cytoskeleton
Type of cytoskeleton linkage depends on context - migrating/collagen-secreting cells (focal adhesion) or epithelial monolayers (hemidesmosomes)
Protrusions adhere to the surface via:
focal contacts containing trans-membrane plasma membrane proteins called integrins
contractile actin bundles (stress fibres) attach to focal contacts
Protrusions and focal points
Protrusions adhere to the surface via:
- Focal contacts containing trans-membrane plasma membrane proteins (integrins)
- Contractile stress fibres (actin bundles) attached to focal contacts
Different types of cadherins
Epithelial cadherins - E-cadherins
Muscle cadherins - N-cadherins
Expressing N-cadherin instead of E-cadherin makes cells highly motile.