Session 12 - Lecture 1 - Cartilage Flashcards
1 - Title
Cartilage
(and endochondral ossification)
{Cartilage & bone - 2 major components in skeletal system
Ossification = the formation of bone}
2 - This lecture should help you to be able to:
- describe the composition of cartilage in terms of its cells and extracellular components.
- classify the 3 major types of cartilage, describing the structural differences between them.
- relate the different anatomical distribution of the 3 major types of cartilage to their different functions. E.g.:
- hyaline cartilage (in the trachea and bronchi)
- hyaline articular cartilage (on articulating ends of bones)
- elastic cartilage (in epiglottis and pinna)
- fibrocartilage (in intervertebral discs)
{1. one of the hallmarks of connective tissue (CT) (Prof London’s lecture) – cells often separated by q large amounts of extracellular (EC) tissue - unlike a lot of other tissues
- only 3
3b. HAC on end of virtually every articulating bone we have
3c. in various positions where we need a lot of elasticity - in positions where theres a gr8 deal of shear force in skeletal system}
3 - Cartilage structure
Cartilage is an avascular tissue that consists of an extensive extracellular matrix in which lie chondrocytes.
The chondrocytes produce and maintain 4the extracellular matrix.
{Cartilage under microscope - like epithelia, cartilage is probs only other tissue that is avascular – got no blood supply
Edge of cartilage – perichondrium – tissue lying on edge of cartilage, and here’s a cartilage proper – cells q flattened towards edge, and they round up – nuclei and nucleolus and various intracellular inclusions. Chondrocytes – prefix chondro always refers to cartilage – produce ECM throughout our lives.}
4
The large ratio of glycosaminoglycans (GAGs) to type II collagen in the cartilage matrix permits ready diffusion of substances between the chondrocytes and the blood vessels surrounding the cartilage.
The extracellular matrix is solid and firm, but also rather pliable and therefore resilient to the repeated application of pressure.
The large amount of hyaluronic acid in the extracellular matrix assists this resilience to the repeated application of pressure.
{Lots of GAGs in cartilage, a high ratio of those to type II collagen fibrils – these are thinner and finer than type I bundles you see in skin and dermis. Type II collagen is a feature of cartilage. Together the GAGs and type II collagen, but particular the GAGs, permit ready diffusion of substances through the cartilage – so these cells live by diffusion of o2, gases and nutrients from the blood supply bc there are blood vessels out here but none in the cartilage itself. So nutrients must be obtained via diffusion from periphery.
So the ECM is solid and firm, but pliable too – therefore resilient to repeated app. of pressure – properties of GAGs, diff GAGs which make cartilage particularly able to withstand pressure – to give a bit but spring back – to be resilient. And partly it’s because GAGs are polar molecules – that therefore attract water and hold a huge amount of water – that water doesn’t exit and enter easily but there’s a lil bit of give when there’s pressure on our joints. We all shrink by a lil bit every day – if we’ve stood up all day we’re just a fraction shorter – a measurable distance bc water gradually leaves cartilage in intervertebral discs, and seeps back again at night as you sleep.}
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