MSK Flashcards
What is the structure of a collagen fibre?
AA chain
Collagen chain
3 collagen chains form helix
Group to form fibril
Group to form fibre
What is the primary structure of collagen?
Triple repeat of glycine and 2 other AAs
Allows collagen to form chains and crosslinks
What is the structure of type 1 tropocollagen?
3 collagen chains- 2 alpha 1 chains, 1 alpha 2 chains form 3-stranded tropocollagen molecule
What happens in processing of type 1 collagen?
Ends (P1NP, P1CP) are cleaved off and released into circulation
What does tropocollagen go on to form?
tropocollagen modules are assembled into a collagen fibril
What holds tropocollagen molecules and fibrils together?
tropocollagen molecule and the fibril are held together by covalent crosslinks (both intra and intermolecular) derived from lysine/hydroxylysine side-chains
What are the different ways of joining collagen?
Covalent cross links within and between helix and tropocollagen- needs copper
H bonds within triple helix- needs vit c
How is collagen broken down?
collagenases and cathepsin K in bone break down collagen
normal for repair and replacement
can become pathological
What happens when type 1 collagen breaks down?
The telopeptides (NTX and CTX) are removed
What are the types of collagen and what are they for?
Type I – bone, tendon, ligaments, skin
Type II – articular cartilage, vitreous
Type III – alongside Type I – wound healing
Type IV - basal lamina
Type V – cell surfaces
Type X – growth plate
What is the shape of long bones?
tubular shape with hollow shaft and ends
expanded for articulation with other bones
What is the shape of short bones?
cuboidal in shape
What is the shape of flat bones?
plates of bone, often curved, protective function
What shape are sesamoid bones?
round, oval nodules in a tendon
What are cortical bones?
Dense, solid, compact
only spaces are for cells and blood vessels.
What are trabecular bones?
Network of bony trabeculae, looks like
sponge, many holes filled with bone marrow.
Cells reside in trabeculae and blood vessels in holes
How is woven bone made?
Made quickly
Disorganised
No clear structure
How is lamellar bone made?
Made slowly
Organised
Layered structure
What is the adult bone composition?
10% water
50-70% mineral, hydroxyapatite
20-40% organic matrix (90% type 1 collagen)
What is the function of hollow long bone?
keeps mass away from neutral axis
minimizes deformation
What is the function of trabecular bone?
gives structural support while minimizing mass
What is the function of the weak ends of bones?
spreads load over weak, low friction surface
What is the function of flat bones?
Protective
What are the cells of bone and what are they like?
Osteoclast- multinucleated
Osteoblast- plump, cuboidal
Osteocyte- stellate, entombed in bone
Bone lining cell- flattened, lining the bone