Collagen + connective tissue

Question 1

What is the function of connective tissue?

Answer 1

highly specialised
mechanical support/movement
contains blood vessels/nerves
arena for fighting infection
regulates cell behaviour

Question 2

4 components of connective tissue

Answer 2

fibres = collagen/elastic fibres
‘ground substance’ = proteoglycans
‘matricellular proteins’
cells = fibroblasts (skin, tendon, ligament), chondrocytes (cartilage), osteocytes (bone)

Question 3

Function of elastic fibres

Answer 3

structural role
regulatory role (growth factor signalling)

Question 4

Describe proteoglycans and their function

Answer 4

important for material properties
variable in size
glycosaminoglycan (GAG) side chains
hold water in tissues, confer viscoelastic properties, interact with cells, cytokines + collagen

Question 5

Function and structure of aggrecan

Answer 5

forms multimeric aggregates in cartilage
link protein stabilises binding to hyaluronan
bih complexes = hydrophilic
increase turgor pressure in tissue = resists compression

Question 6

Structure and function of collagen

Answer 6

collagen fibrils = structural component
3 alpha chains = triple helix
each alpha chain single gene product
3 identical chains = homotrimer
2/more different chains = heterotrimer
unique amino acid composition (Gly-X-Y repeats, X= proline, Y = hydroxyproline)
triple helix = stabilised by hydrogen bonds, proline + hydroxyproline = stability + rigidity

Question 7

What occurs during intracellular collagen processing?

Answer 7

essential for stability
post-translational modification = hydroxylation, glycosylation
assembly of 3 alpha chains
disulphide bond formation
assembly of triple helix

Question 8

What type of collagen is in lamella of bone?

Answer 8

type 1
(tendon tensile strength also determined by parallel type 1 collagen fibril bundles)

Question 9

What type of collagen is in cartilage?

Answer 9

mesh of type 2 collagen + aggrecan

Question 10

What happens to cartilage in osteoarthritis?

Answer 10

loss of proteoglycan (aggrecan)
collagen fibrillation
enzymatic degradation

Question 11

What is the structure of entheseal fibrocartilage?

Answer 11

distinctive matrix organisation + composition

type 2 cartilage + aggrecan

Question 12

What changes occur in tendinopathy?

Answer 12

degenerative condition
fibrochondroplasia (abundant rounded cells + increased GAG/proteoglycan)
loss of collagen fibril organisation + decreased fibril diameters
increased type 3 collagen
vascular (+nerve) infiltration
failure to repair

Question 13

What is a collagenopathy? Give some common examples

Answer 13

genetic diseases of collagen
mutations in collagen genes coding for different collagen types
osteogenesis imperfecta = type 1
achondrogenesis = type 2
vascular EDS = type 3
alport syndrome = type 4
classical EDS = type 5

Question 14

What is a missense mutation?

Answer 14

change of single base pair causes substitution of different amino acid in protein