V.C - F - Cartilage Structure&Function in column - Role/development/composition - hyaline/elastic/fibrocartilage - pathology Flashcards
What is cartilage and what is it made up of?
Cartilage is a semi-rigid connective tissue made up of chondrocytes and a vast gel-like extracellular matrix
What are the three main types of cartilage?
The three main types are hyaline cartilage, white fibrocartilage and elastic cartilage
What is cartilage and what is it made up of? What are the three main types of cartilage? What is the function of cartilage? (provides 4 things)
Cartilage is a semi-rigid connective tissue made up from chondrocytes and a vast gel like extra-cellular matrix The three main types are * Hyaline catilage * White fibrocartilage * Elastic cartilage Cartilage provides mechanical stability, stability, strength, rigidity and some elasticity
What is the blood supply to cartilage?
Cartilage is avascular
Now we shall explain the role and development of chondrocytes What are chondrocytes?
Chondrocytes are mature cartilage cells which make up the cellular component of cartilage
There is a high matrix to cell volume ratio in the cartilage Chondrocytes occupy approximately what percentage of the total cartilage tissue? Why are chondrocytes relatively metabolically inactive?
Chondrocytes occupy approximately 1-10% of the total cartilage tissue Chondrocytes are relatively metabolically inactive due to the absence of vascular supply and innervation
What is the functional unit of cartilage known as?
The functional unit of cartilage is known as the chondron
What is the functional unit of cartilage made up of? What is the name of the pericellular covering of the cells in the chondron?
It is made up of the chondrocytes and its pericellular covering (glycocalyx) - glycococalyx is the pericellular matrix covering the chondrocytes
To summarise, chondrogenesis (also known as chondrification) is the process by which cartilage is formed from condensed mesenchymal tissue, to chondroblasts to chondrocytes Lets break down the development How do mesenchymal stem cells become chondroblasts?
Mesenchymal stem cels undergo condensation to become chonrodprogenitor cells which undergo proliferation and differentiation to become chondroblasts
What are chondroblasts? How do chondroblasts become chondrocytes?
Chondroblasts are immature cartilage cells and differentiate and mature to become chondrocytes (mature cartilage cells)
What is the terminal differetiation that chondrocytes undergo and why?
Chondrocytes undergo a terminal differentiation and hypertrophy to become specialized to a specific type of cartilage - hyaline cartilage, fibrocartilage or elastic cartilage
Describe the development of cartilage from mesenchymal stem cells to hypertrophic chondrocytes What is this process known as?
https://s3.amazonaws.com/classconnection/403/flashcards/11907403/png/ppngjpgpngjpg-167FECD55785197BA5D.png
If a chondrocyte continues to differentiate after becoming a hypertrophic chondrocyte, what does chondrogenesis progress to and where does this occur?
If chondrocytes continue to differentiate, then chondrogenesis progresses to endochondral ossification which only occurs at epiphyseal growth plates
There are roughly 6 stages of endochondral ossification Describe the first three stages?
The foetal hyaline cartilage model develops The cartilage then begins to degenerate & calcify & a periosteal bone collar forms around diaphysis Primary ossification centre forms in the centre of the diaphysis with blood vessels & capillaries supply the diaphysis & epiphysis
What happens in the latter three stages of endochondral ossification?
Secondary ossification centres appear in the epiphyses Bone replaces cartilage, except at the epiphyseal growth plates and the articular surfaces The epiphyseal growth plates ossify forming epiphyseal lines and the articular surfaces of cartilage remain
Describe all 6 stages of endochondral ossification
https://s3.amazonaws.com/classconnection/403/flashcards/11907403/png/ppngjpgpngjpgpngjpg-167FEDD4B233A3D512E.png
Chondrocytes are important for both the structure and function of cartilage Chondrocytes have a dual function where they can regulate what?
Chondrocytes have a dual function where they can regulate both cartilage synthesis and degradation
How do chondrocytes regulate cartilage synthesis? (they secrete components of ___? Try name these components)
Chondrocytes proliferate and secrete components of the extracellar matrix - collagen, proteoglycan, glycoproteins and hyaluronan
How do chondrocytes regulate cartilage degradation?
Chondrocytes can produce enzymes that degrade the extracellular matrix - such as collegnase, natural proteinases, cathepsins
State how chondrocytes are important in controlling cartilage synthesis and degradation again
* Chondrocytes has a dual function - to regulate cartilage synthesis and degradation * Chodrocytes regulate cartilage synthesis by secreting components of the extracellular matrix - proteglycons, glycoproteins, collagen, hyaluronan * Chondrocytes can produce enzymes that degrade the extracellular matrix - proteinases, collagenases, cathepsins
What does chondrocytes, degrading potentially damaged extracellular matrix allow for?
Degrading potentially damaged extracellular matrix allows homeostatsis for the cartilage and the turnover of the extracellular matrix
Lets look at the role of chondrocytes specific to articular cartilage Throught the zones of articuar cartilage: superficial, middle and deep zones, the chondrocytes have a different morphology What is different about the morphology in each of these zones?
In the superficial zone of articular cartilage, the chondrocytes are flat and in high density In the middle zone, the chondocytes are round In the deep zone, the chondrocytes are big and usually arranged in vertical columns
The zones of the articular cartilage also have different quantities of the components of the extracellular matrix Name the components found in each of the three zones
In the superficial zone - collagen type II, collagen type IX, collagen type XI, aggrecans In the middle zone - procollagen type I, collagen types IX and XI, decorin, bigylcan and greater amounts of aggrecans In the deep zone - collagen type X, biglycan, decorin, aggrecans, MMP13
Now we have discussed the development of cartilage and its role, we will describe the composition (cellular components and matrix) of cartilage How many types of collagen are there? What is the three chains of crossing over polypeptides that all types of collagen contain at least one of known as?
There are 28 types of collagen found in the human body All types of collagen contain at least one triple helix domain - three polypeptide chains crossing over
What is the function of collagen in the ECM?
It is important for mechanical support, stability and shape
What is the most abundant type of collagen and where is it mainly found and which type of collagen is the main type present in cartilage?
Type I collagen is the most abundant type of collagen found in skin, bone and tendons Type II collagen is the main collagen of cartilage
Which types of cartilage is type I and type II collagen found in? Which is thinner? Which forms fibrils?
Type I collagen is found in only fibrocartilage Type II collagen is found in all types of cartilage and is thinner Both types of collagen are fibril forming
What is the glycoprotein found in the cartilage matrix that specifically promotes the adherence of chondrocytes to type II collagen?
The glycoprotein found in the cartilage matrix that specifically promote the adherence of chondocytes to type II collagen is known as chondronectin
What does the extracellular matrix consist of? The ECM ca be split into pericellular, territorial and interterritorial matrix What is the difference?
The ECM consists of Ground substance - the gel-like substance of the ECM & the fibrous proteins Pericellular matrix is around the chondrocytes in the chondron Territiorial matrix surrounds the chondron Interterritorial matrix is between the chondrons
The ground substance which enables the cartilage to become gel-like and resist deformation through the absorption of water is very good at resisting compressive forces How is ground substance formed?
Ground substance consists of large molecules called glycosaminoglycans (GAG) which become attached to a core protein to form proteoglycans
What is the major structural component of the ECM?
This would be the hyaluronan strand and the linker proteins - allow the proteogylcan aggregates to be formed
What is the extracellular matrix of hyaline cartilage made from?
70% water
30% organic material
* 60% Type II collagen
* 40% protein aggregates
Does the IV disc contain more Type I or Type II collagen in its fibrocartilage? Name some areas with a high compression factor where fibrocartilage is found?
IV disc contains roughly equal quantities of Type I and Type II collagen Present in areas which have a high compression factor IV discs – Connecting fibrocartilage Menisci – Intra articular fibrocartilage Tendons of muscles – Stratiform fibrocartilage Acetabular Labrum - Circumferential fibrocartilage
What type of collagen is found in elastic cartilage? What fibres does it also contain in its matrix? The elastic cartilage allows for structures to maintain their shape and give flexibility, give two examples?
Only Type II collagen is found in elastic cartilage Elastic fibres are found in the matrix Two examples where elastic cartilage is present is the pinna of the ear and the epiglottis
Which types of cartilage have a perichondrium? What is the perichondrium?
Both hyaline and elastic cartilage have a perichondrium Fibrocartilage does not have perichondrium Perichondrium is the layer of connective tissue that usually surrounds cartilage
The perichondrium is derived from mesencyhmal stem cells that flatten and elongate What is the difference between the outer & inner layer of perichondrium? What cells are derived from the pericondrium? What does the perichondrium initiate the invasion of?
The outer layer is fibrous The inner layer is chondrogenic Enodethelial cells (line blood vessels) and osteoblasts (secretes bone) are derived from the perichondrium Perichondrium initiates vascular invasion
NOW WE RELATE THE MICROSTRUCTURE OF CARTILAGE TO ITS FUNCTION IN THE VERTEBRAL COLUMN What is the main function of the vertebral column cartilage? Where are hyaline and fibrocartilage present in the vertebral column?
The main function of the vertebral column cartilage is to resist compression due to loading - cartilage is good at this remember as it is gel-like and can absorb water Hyaline cartilage is found at the articular surfaces Fibrocartilage is found in the intervertebral discs
The articular surfaces are present as hyaline cartilage with a dense extracellular matrix and sparse chondrocytes We discussed the layers of hyaline cartilage as being superficial, middle and deep. What are their other names? What is the morphology of the chondrocytes throughout each layer?
Superficial layer - tangential zone * Chondrocytes are flat and high in density Middler layer - Transitional zone * Chondrocytes are round Deep layer - Deep zone * Chondrocytes are big & in columns
The tangential zone (superficial) is in contact with what? How would you describe the collagen fibres in the tangenztial zone? What percentage of the total hyaline cartilage does each zone take up?
The tangential zone is in contact with the synovial fluid
The collagen fibres in this zone are tightly packed
- Tangential zone: 10-20% of total hyaline cartilage
- Transitional zone: 40-60% of total hyaline cartilage
- Deep zone: 30-40% of total hyaline cartilage
The transitional zone is 40-60% of total cartilage volume What is this the first point for? What does it contain?
The transitional zone is the 1st point for compression resistance It contains proteoglycans and collagen fibrils
Which zone does the highest amount of compressive resistance occur in hyaline cartilage? What is the tide mark?
The transitional zone is the 1st point of compressive resistance but the deep zone is where the highest amount of compressive resistance occurs in hyaline cartilage The tide mark represents the change from uncalcified cartilage to the calcified cartilage that joins the bone
We said earlier the IV disc had roughly equal quantities of type I and type II collagen present The annulus fibrosus is composed of many layers of cartilage. What are these concentric layers known as? Where are these found in the annulus fibrosus?
These concentric layers of cartilage in the annulus fibrosus iare known as lamellae The type I collagen is found more at the periphery of the annulus fibrosis The type II collagen is found closer to the nucleus pulposus in the annulus fibrosis
What type of joint is a facet joint and what is its other name? What are the articulations? What is the function of a facet joint? (include what it limits and where specifically)
Zygapophyseal joint is a synovial plane joint formed between the articulations between superior and inferior articular facets of neighbouring vertebrae Function Influences flexion and extension Limits axial rotation - especially at T12/L1 Involved in load transmission
Intervertebral discs allow for the indirect articulation of vertebral bodies. The articular surfaces of cartilagenous joints are connected entirely by cartilage (ie no synovial fluid present) Name sites where primary and secondary cartilaginous joints are present?
Primary cartilaginous joints - at the epiphyseal growth plates and at the joint between 1st rib and sternum Secondary cartilaginous joints - IV discs and pubic symphysis
How many IV discs are there in the vertebral column? What is the general consensus of disc thickness as you go down the vertebral column? What are the three parts of the IV discs?
There are 24 IV discs The discs increase in thickness as you descend down the vertebral column - apart from becoming thinner in the upper thoracic vertebrae Three parts Inner nucleus pulposus Outer annulus fibrosus Superior and inferior Cartilaginous end plate
Describe the structure of the cartilage in the annulus fibrosus? - the concentric layers, types of collagen, fibres between the layers, cell morphology
Concentric layers of cartilage known as lamellae with elastin fibres between lamellae Tyep 1 collagen in the outer part and type 2 collagen closer to the nucleus pulposus Cell morphology Outer region - fibroblast-like, thin and elongated Inner region - oval
What is the function of the cartilage in the annulus fibrosus?
Shock absorber Components of extracellular matrix keep the disc hydrated Disc is able to return to its original shape due to the elastin fibres between lamellae Anchors tissue to bone Tensile strength due to collagen fibres
Talked about the structure and function of cartilage for the facet joints and Iv disc, lets now talk about the end plates of the vertebral column Vertebral endplate Cartilaginous endplate What is the difference between them? where are they? Where is the cartilaginous end plate thickest?
Veretbral end plate is a thickened layer of cortical bone at superior and inferior to the surface of the vertebral body Cartilaginous end plate is a thin layer of hyaline cartilage between the vertebral end plate and nucleus pulposus Cartilaginous end plate is thickest at its outer edge
How is the cartilage affected in spondylosis? (due to chondrocyte dysfunction)
Cartilage degeneration occurs with age There is chondrocyte hypertrophy and dysfunction as well as the chondocytes producing increased proteolytic enzymes which degrade the extracellular matrix and reduce hydration Affects IV discs and facet jints
What is thought to be the reason for disc degeneration in intervertebral osteochondrosis? What pathological changes occur?
Dysfunction of the end-plates are responsible for the disc degeneration - ectopic calcification occludes vascular channels blocking nutrient supply to the disc Annulus fibrosus becomes disorganised Nucleus pulposus becomes more fibrotic and less organised with age
What is uncovertebra arthosis? Where are the uncovertebral joints and what are they better known as?
Uncovertebral arthrosis is osteoarthritis specific to the joint between the uncinate processes which exist as hook shaped projections on the superior surface of cervical vertebral bodies C3-C7 The uncovertebral joints are better known as the joints of Luschka
