Lecture 9 - General principles of bone 2 Flashcards
What are some important features about cartilage?
It’s resilient, and is resistant to compression. Cartilage acts to distribute weight over bone, and by doing this it reduces impact and wear on the bone
How do chondrocytes survive within cartilage if it is avascular?
The ECM is permeable, this allows oxygen to diffuse through to the chondrocytes The avascular nature of cartilage means that it takes much longer to heal compared to regular bone
What are the three types of cartilage in the body? Compare them to each other
Hyaline
Elastic
Fibrocartilage
Hyaline cartilage is compressible due to its high water content, but is not as elastic as elastic cartilage. Fibrocartilage is for when stress resistance is needed rather than movement
How is cartilage similar to bone?
There is a cellular component, a chondrocyte, which lies in an ECM. What differs between the cartilage and the bone is the fibres and the ground substance of the ECM
Which fibers are more predominant in elastic cartilage than in hyaline cartilage?
Elastic cartilage has more elastic fibres, but since hyaline cartilage is more for stress resistance it has more collagen fibers
Where is hyaline cartilage found?
Places of articulation - known as articular cartilage
Where is elastic cartilage found?
Found in the external ear and epiglottis The ECM of elastic cartilage has both hyaline and elastin fibers
What fiber is more predominant in fibrocartilage?
Collagen fibers This is because fibrocartilage is designed to resist compression and shearing forces
What are the components of hyaline cartilage, and their percentages?
ECM - 60-80% water
Type ll collagen - 15%
Proteoglycans (+GAGs) - 15% -> this is aggrecan
Adhesive glycoproteins - 5%
Cells - 3-5%
What component of hyaline cartilage allows it to hold water?
The aggrecan (cartilage specific proteogylcan + GAGs) is very negative, and this attracts water
What holds the different components of the cartilage ECM together?
Adhesive proteins
What conditions do chondrocytes live under?
Low oxygen tension, they must get their oxygen via diffusion and compression. Movement assists in water movement, which circulates the dissolved O2
What is the name of the connective tissue which covers non-articular hyaline cartilage? And how does this supply the cartilage will cells?
Perichondrium
In the perichondrium there are fibroblasts, these differentiate into chondroblasts, and then into chondrocytes
Does articular cartilage have a perichondrium?
NO Renewal of cells comes from deep within cartilage, but this is much slower
How are chondrocytes programmed to die?
They calcify themselves in the matrix and then die. The dead chondrocytes provide a zone where osteoprogenitor cells can invade and proliferate
