Cytoskeleton, Junctions, ECM

Question 1

Microfilaments

Answer 1

Composed of Actin
6-8 nm in diameter
Structural function, microvilli, filopodia, gives shape to cell
forms tracts for myosin, giving contractility

Question 2

Intermediate Fibers

Answer 2

different in various tissues; vimentin (mesenchymal origin) cytokeratin
about 10 nm in diameter
anchors, structural
not contractile

Question 3

Microtubules

Answer 3

Tubulin
about 25 nm in diameter
monorail system for kinesins (motor protein complex)
cilia and flagella (dynein)

Question 4

Tight Junctions

Answer 4

homotypical interactions between transmembrane proteins
very narrow gaps, controls movement between cells
maintains cell polarization
Caludins, occludin, JAM
binds internally to actin microfilaments
various roles in cell signalling

Question 5

Cell to Cell (zona adherens)

Answer 5

holds cells together
cadherins (outside, ca 2+ dependent) and cantinins (inside)
nectin-afadin complexes (contact inhibition-stop growing)
Vinculin and actinin attachments to actin filaments
Gaps of 20 nm

Question 6

Focal Adhesion Joints

Answer 6

Holds cell to ECM
similar to cell to cell except integrins replace cadherins as transmembrane component (and goes to ecm)
integrins interact with ecm protein (collagen, fibronectin, ect)
integrin does cell signalling
attach to actin filaments

Question 7

Desmosomes

Answer 7

cell to cell
cadherins (outside) called desmoglein and desmocollin
catinins (inside) called desmolankin, phakiglobin, plakophilin
Forms lines externally, visible plaques and electron dense
attach to intermediate fibers
gaps of 25 nm
help resist shearing forces

Question 8

Hemidesmosomes

Answer 8

Cell to matrix
also has intracellular plaque
attach to intermediate filaments
integrin is transmemebrane protein
resist shear
anchor to basal lamina

Question 9

Gap junctions

Answer 9

cell to cell aqueous pores
6 connexins to make 1 connexon
2 nm pore between cells that are 2-3 nm away from each other
ions and small water soluable molecules
Nucleic acids, sugars, proteins are too large
propagate electrical signals

Question 10

Basal Lamina

Answer 10

ECM sheet attatching epithelium to CT
hemidesmosomes
50-100 nm thick
3 zones ( cell -lamina lucida, laina densa, lamina fibroreticularis (epthelial tissues) CT)

Question 11

Fibroblasts

Answer 11

Main “go-to” cell of CT
highly motile, involved in tissue repair
rarely have cell-cell connections (except PDL)
often have cytoskeletal (actin) connections from integrins to fibronectin in the ECM (fibronexus)
many subtypes in many different tissues
fibroblasts age -slower healing with age?
incredible diversity of secretory products

Question 12

Collagen

Answer 12

Triple helical structure ( 3 twisted strands)
most abundant protein
major synthetic product of mesenchymal derived cells
rich in proline and lysine
Dentine= type 2, some 3. Pulp=1 and 3, Cartilage= 2
5 microfibils with a stagger
bone/dentin- mineral deposit in gap regions
diseases like scurvy and osseogenesis imperfecta

Question 13

Elastin

Answer 13

fibroblast product
assembled into sheets or fibers
glycoproteins fibrillin 1 and fibrillin2 form a microfibril scaffold which elastic accumulates onto
marfans syndrome

Question 14

CT Ground Substance

Answer 14

proteoglycans and glycoproteins
gell like, very hydrated
sequesters fluid and gives compressive strength

Question 15

Proteoglycans

Answer 15

made from fibroblasts
protein core with glycosaminoglycan (GAG) chain
GAGS- disacharide units of hexosamines and uronic acid
strong negative charge, hydophilic
hyaluronic acid and versican are example
can serve to sequester growth factors in ECM and can help activate GF receptors

Question 16

Glycoprotein

Answer 16

Proteins (have more than proteoglycan)with carb side chains
fibronectin (cell migration/ wound healing)
tenascin (directs migration)
thrombospondin (attatchment, migration, collagen alignemnt)