Lecture 4: Tissues under load 2 Flashcards
describe what happens in scurvy
deficiency in vitamin c means collagen cannot for the essential coiled structure.
- most prevalent in areas where there is a high rate of collagen turnover
what are the symptoms of scurvy?
slow wound healing, sore gums (peridontal ligament), bleeding from mucous membranes
describe the cause of osteogenesis imperfecta
an inherited/genetic disease which occurs due to a mutation in the genes that encode collagen type one
what happens if someone has osteogenesis imperfecta?
collagen type I is of poor quality, as it isnt coiled properly in bones
symptoms are: brittle bones, bone deformations, weak tendons, abnormal skin
which type of collagen does stickler syndrome affect?
type II
proteoglycan = ?
core protein + glycosaminoglycans
what is hyaluronan?
a large glycosaminoglycan which isn’t sulfated and doesn’t attach to a core protein.
what property of tissues does hyaluronan provide?
mechanical support and lubrication/viscosity
what are the three common features of glycosaminoglycans?
- longer, linear carbohydrate chains
- chains of repeating disaccharide units including glucosamine
- negatively charged due to occurence of sulphate and uronic acid groups
how does the negative charge of the glycosaminoglycans contribute to the tissue they are in?
the negative charges repel each other and ‘take up space’ positive ions are pulled towards the negative, and brings water with them, which causes the tissue to be able to resist compressive load
true or false: the water brought into cartilage allows it to resist compressive load as the water is compressed
partially true, but water is not compressed, instead, it flows in and out of the tissue as compressive loads are applied and removed.
what is aggrecan?
the major proteoglycan of cartilage
what two GAGs is aggrecan rich in?
keratin sulfate and chondroitin sulfate
__________ proteoglycans bind to a _____________ glycosaminoglycan via link proteins
aggrecan, hyaluronan
what are the two main enzymes that contribute to ECM turnover and remodelling?
Collagenases and metalloproteases
what is the role of elastin?
the protein in elastic fibres, which provides recoil, flex and elasticity of skin etc
what is the role of fibronectin?
attaches cells to the ECM
- binds to a cell transmembrane protein and to collagen fibers extracellularly
what are the two ways to think about bone in terms of relating structure to its mechanical properties?
- micro-organisation
- macro-organisation
how does the micro organisation of bone relate to its mechanical properties?
orientation of collagen fibres in lamellae resist tensile forces from different angles
crystalline structure provides resistance to compression
what are the percentages of bone makeup?
- 25% water
- 60-70% minerals (resists compression)
- 5-10% collagen
compact bone is organised in ___________ lamellae, which spongy bone is organised in _________ lamellae
concentric, parallel
how does the macro organisation of bone relate to its mechanical properties?
compact bone is organised to resist strong forces in one direction
spongy bone has trabeculae organised so that it aligns with load/forces applied on it
what is Ward’s triangle?
the weakest section of the epiphysis in terms of trabeculae
how is spongy bone responsive?
when a load is applied onto our bones, the trabeculae respond to this stimuli and concentrate their growth along the lines of force
what is Wolff’s law?
basically the more you load the bone the stronger it gets
what does wolff’s law tell us about astronauts bones?
since they are not loaded, they will experience bone loss
what is the process of healing a bone?
- bone breaks and a fracture hematoma forms due to macrophages. mesenchymal stem cells come in
- MSC -> chondroblasts and created cartilage callus.
- new BVs grow into callus and calcify it
- osteoblasts replace calcified cartilage with bone
what is the purpose of spongy bone?
to decrease the weight of the bone and to distribute the weight/load over a larger surface area
