Tissue Organization Flashcards
What are the two principle types of tissues?
Cellular (muscle/epithelia)
Connective (cartilage/bone/tendon)
What are cellular tissues’ integrity and properties from? (2 types of interactions)
cell-cell interactions
cell-extracellular matrix interactions
What are crucial for cellular tissue integrity?
cell junctions
What are the properties and of connective tissue derived from?
extracellular matrix (ECM) composition
What is the role of the ECM in connective tissues?
anchorage point for cells - connective tissues are primarily comprised of ECM
What main molecules interact in adhering/anchoring junctions?
actin microfilament cytoskeleton, intermediate filament cytoskeleton
What are the 3 basic components of a junction?
- Transmembrane glycoprotein
- linker proteins
- cytoskeleton
what do linker proteins do?
stabilize link from tissue to cytoskeleton
what are the two types of actin-filament (MF) based anchoring junctions?
adherens junction = cell-cell
focal junction = cell-ECM
what transmembrane protein do adherens junctions use?
cadherins
what transmembrane protein do focal junctions use?
integrins
What are the two types of intermediate filment based anchoring junctions?
desmosome = cell-cell hemi-desmosome = cell-ECM
what transmembrane protein do desmosome junctions use?
cadherins
what transmembrane protein do hemi-desmosomes use?
integrins (alpha6/beta4)
are cadherins and integrins homo- or heterophilic?
cadherins = homophilic integrins = heterophilic
what are the two blistering disorders associated with anchoring/adhering junctions?
Pemphigus - autoimmune - antibodies to cadherins
Epidermolysis bullosa simplex - defects in intermediate filament (keratin) assembly
What are the two functions of tight junctions?
- permeability barrier at epithelial sheets (ex. SI)
2. maintain cell polarity (ex. mem proteins)
What are the 4 types of junctions in cellular tissue?
- Actin-Filament based anchoring junctions
- Intermediate Filament based anchoring junctions
- Tight junctions
- Gap junctions
what is the function of gap junctions and where are they used/what for?
communication btw neighboring cells
electric conduction in cardiac cells
When a gap junction is CLOSED, what are the intracellular conditions?
High Ca2+
Low pH
When a gap junction is OPEN, what are the intracellular conditions?
Low Ca2+
high pH
What single protein comprises a gap junction?
Connexin
what does the ECM confer connective tissues?
tensile strength
elasticity
permeability
what are the three types of ECM?
- Fibrillar proteins
- Bulky fillers
- Cross-linkers
What are the fibrillar proteins of connective tissue?
collagen
elastin
fibrillin
What are the bulky fillers of connective tissue?
proteoglycans
what are the cross-linkers of connective tissue?
fibronectin, laminin
What type of protein is collagen?
Fibrillar protein
What is Ehlers-Danlos syndrome?
defect in collagen/fibrillar proteins
hyperextensible skin and joints
what does collagen confer?
tensile strength
resistance to stretching
how is non-fibrillar collagen different from fibrillar collagen?
non fibrillar pro-peptide is not cleaved - cannot form fibrils
non-fibrillar collagen is found in basil lamina
what type of collage is found in the basal lamina?
non-fibrillar collagen
what component of elastin makes it elastic?
proline!
what does fibrillin do?
stabilizes elastin - resists stretching
What do mutations in fibrillin do?
Marfan syndrome –> aortic rupture possible
What are characteristics of glycosaminoglycans?
protein backbone
sulfated, carboxylated
what do cross-linking proteins (fibronectin, laminin) do?
integrate cellular and connective tissue
What do cross-linking proteins have multiple binding sites for?
integrins
where would cross-linking proteins be found?
loose connective tissue, blood clots, wound repair, cell migration, development
what are the 4 functions of the basal lamina?
- supports muscle cells (role in DMD)
- supports epithelial sheets (cell prolif)
- molecular filter for kidney
- guidance pathways - development (Periph NS)
What are the 4 factors of growth control?
- Cell lineage (apoptosis, telomere length)
- External/diffusible factors (GF)
- cell-ECM interactions
- cell-cell interaction (growth inhibition)
What are cell lineage factors of growth control
apoptosis
telomere replication - too short –> senescence
what differences do transformed (cancer) cells have in terms of growth control?
do not senesce (inactive telomerase or p53)
lack GF dependence
lack anchorage dependence
no cell-cell contact inhibition
in which two types of genes to cancerous mutations occur?
oncogenes
tumor suppressor genes
