Cartilage Flashcards
what is cartilage?
- a semi rigid connective tissue
what is cartilage made up of?
chondrocytes and a vast gel-like extra-cellular martix
what does cartilage provide?
mechanical stability, strength, rigidity and some elasticity
what does cartilage resist?
compression
is cartilage vascular or avascular?
avascular
what are the 3 main types of cartilage?
hyaline, white fibrocartilage and elastic cartilage
what are chondrocytes?
the cellular component of cartilage- mature cartilage cells
chondrocytes occupy how much of total cartilage tissue?
1-10%
are chondrocytes metabolically active or inactive?
inactive- absence of vascular supply and innervation
what is a chondron?
functional unit composed of a chondrocyte and its pericellular covering
progression from mesenchymal stem cells go to what?
chondroblasts
chondroblasts mature and go to what?
chondrocytes
mesenchymal tissue is derived from what?
paraxial and lateral plate mesoderm, posterior to the primitive streak
undifferentiated mesenchymal cells do what?
migrate and undergo condensation
chondroprogenitors proliferate and do what?
differentiate to form chondroblasts
chondroblasts further differentiate and do what?
mature to form chondrocytes
chondrocytes undergo what?
a terminal differentiation and hypertrophy to become specialised to a specific type of cartilage; hyaline, fibrous or elastic
what is the development of chondrocytes called?
chondrogenesis
what are the stages in the development of chondrocytes?
condensation, proliferation and differentiation, differentiation and maturation, terminal differentiation
if chondrocytes continue to differentiate what occurs?
continue to differentiate tot chondrogenesis processes to endochondral ossification which only occurs at epiphyseal growth plates
what are some roles of chondrocytes?
important for both structure and function of cartilage
chondrocytes proliferate and secrete what?
components of the extracellular matric – collagen, glycoproteins, proteoglycans, hyauronan.
chondrocytes regulate what?
cartilage synthesis and cartilage degradation.
chondrocytes can produce what?
enzymes that degrade components of the extracellular matrix – collagenase, neutral proteinases, cathepsins.
chondrocytes have a dual function doing what?
where they can both regulate synthesis and degradation of cartilage.
potential damage to the extracellular matrix means what?
matrix is replaces and so cartilage is maintained
what is the superficial zone of chondrocytes?
collagen types II, IX, X, aggrecans, lubricin
what is the middle zone of chondrocytes?
collagen types II, IX and X, biglycan, decorin, greater amounts of aggrecans
what is the deep zone of chondrocytes?
collagen type X, biglycan, decorin, aggrecans, MMP13
how many types of collagen are present in vertebrates?
28
what kind of protein is collagen made from?
elastic proteins
what kind of resilience does collagen have?
90%, not permanently deformed
what do all collagen contain?
1 triple- helical domain
where is collagen present?
in the Extra cellular matrix
what does collagen provide in the ECM?
stability, shape, mechanical
type I collagen is found where?
bones, skin and tendons
type II collagen is found where?
main collagen of cartilage
type I collagen is present in what?
present in fibrocartilage
type II collagen is present in what?
in all cartilage
what cartilage is most abundant ?
type I
which is a thinner cartilage?
type II
what do type I and type II cartilage form?
fibrils
Glycoprotein chondronectin promotes what?
adherence of chondrocytes to the type II collagen matrix
what does the extracellular matrix in cartilage consist of?
ground substance & fibrous proteins
what kind of matrix is the extracellular in cartilage?
pericellular, terrirotrial interterritorial matrix
cartilage can resist what?
deformation through water absorption.
glycosaminoglycans become attached where?
to a core protein module which will then be attached and stabilised by a link protein to the hyaluronan strand.
major structural component in ECM in cartilage are what?
hyaluronan
link protein
hyaline cartilage makes up what?
the majority of cartilage in the body
what type of collagen is hyaline cartilage?
type II collagen
what is present in hyaline cartilage?
perichondrium
where is hyaline cartilage found?
present at articular surfaces
cartilage in ECM contains what?
70% water
25% organic material (60% type II collagen, 40% protein aggregates)
fibrocartilage contains what?
Type I collagen
what is the strongest cartilage?
fibrocartilage
where is fibrocartilage found?
in soft tissue- to-bone attachments
does fibrocartilage contain perichondrium?
no
what percentage of collagen does the IV disc contain?
same quantities
what type of fibrocartilage is in IV discs?
connecting fibrocartilage
what type of fibrocartilage is in menisci?
intra articular fibrocartilage
what type of fibrocartilage is in tendons of muscles?
stratiform fibrocartilage
what type of fibrocartilage is in acetabular labrum?
circumferential fibrocartilage
what is the only type II collagen?
elastic cartilage
what does elastic cartilage contain?
elastic fibres in matrix
does elastic cartilage contain perichondrium?
yes
what does elastic cartilage allow?
for structures to maintain their shape and give flexibility
where would you find elastic cartilage?
pinna of ear, epiglottis
what is perichondrium?
connective tissue which usually surounds cartilage
where is perichondrium derived from?
mesenchymal cells- flatten and elongate
what are the 2 layers of perichondrium?
outer fibrous layer and inner chondrogenic layer
what cells are derived from perichondrium?
osteoblasts and endothelial cells
what is the function of perichondrium?
Regulates the initiation of vascular invasion
Vasculogenic/angiogenic programme
Main function of the vertebral column cartilage is what?
is to resist compression due to loading.
In articular cartilage and intervertebral disc collagen provides what?
the ability to resist compressive loading so protecting the cells from injury by mechanical trauma.
Hyaline cartilage and fibrocartilage are present where?
Hyaline at articular surfaces
Fibrocartilage in the IV discs
what are the 3 zones present in articular surfaces?
hTangential zone
Transitional zone
Deep zone
what is the tangential zone in contact with?
with synovial fluid - resist a variety of forces
how much does the tangential zone make up?
10-20% of total thickness
how are collagen fibres arranged in the tangential zone?
tightly packed
is there a high or low number of chondrocytes in the tangential zone?
high number
how much does the transitional zone make up?
40%-60% total cartilage volume
what does the transitional zone make up?
proteogylcans and collagen fibrils
how is the organisation in the transitional zone?
collagen and chondrocyte organisation
where is the 1st point for compression resistance?
transitional zone
how much does the deep zone makeup?
30% of total cartilage volume
what is the orientation of the deep zone?
collagen fibres arranged perpendicular to surface
in the deep zone what is the content of proteoglycan and water?
high proteoglycan and low water content
the deep zone has greatest resistance to what?
compression
the annulus fibrosis is composed of what?
many layers of cartilage
in relation to the annulus fibrosis where is type I collagen found?
at periphery
in relation to the annulus fibrosis where is type II collagen found?
closer to the nucleus pulposus
The presence of cartilage in the vertebral column is of importance for what?
Flexibility and movement of the spine
Support of body weight
Shock absorber
The cartilaginous sites are where?
Zygapophyseal (facet) joint – hyaline cartilage
Intervertebral disc – fibrocartilage
Cartilagenous end plate – hyaline cartilage
what kind of joint is the zygapophyseal joint?
synovial planar joint
where is the zygapophyseal joint?
an articulation between superior and inferior articular processes of neighbouring vertebrae
what is the function of a zygapophyseal joint?
Influences flexion and extension
Little effect on lateral flexion
Restricts axial rotation
Involved in load transmission through posterior elements – facet joint thought to transmit 3-25% of segmental load (increases in disease)
The articular surfaces of a zygapophyseal facet joints are covered with what?
hyaline cartilage
does the layer of cartilage of the zygapophyseal joint vary and where?
yes along the vertebral column
is the thickness of hyaline cartilage consistent within each facet joint in relation to the zygapophyseal joint?
not consistent, The layer of cartilage becomes thicker towards the centre of the articular surface
Peak thickness level is approximately 1 mm
There is some debate regarding the complete covering of the articular surfaces with hyaline cartilage [Jaumard et al. (2011)] what is this?
Some believe the extremities of the articular surfaces have bone exposed
One study found the level of exposed bone to be highest in the upper cervical region (3 times more than the lower cervical region)
There is less cartilage coverage in females – this claim is backed by the greater incidence of neck trauma in females
what is the main function of hyaline cartilage present in the zygapophyseal joint is what?
to reduce friction during movement and to increase lubrication (along with the synovial fluid produced)
what is another function of hyaline cartilage present in the zygapophyseal joint?
it plays some role in bearing compressive tensile forces and shear loads
This is due to the structural arrangement of the cartilage tissue
As well as the increased presence of proteoglycans in deeper zones which can absorb water and reduce compressibility of cartilage
The extracellular matrix of cartilage tissue is a laminate structure with 3 zones which are?
superficial, middle and deep zones
IV discs allow what?
allow for the indirect articulation of vertebral bodies.
The articular surfaces of cartilaginous joints are connected by what?
entirely by cartilage,
where are primary and secondary cartilaginous joints found?
Primary cartilaginous – epiphyseal growth plate Secondary cartilaginous (symphysis) – intervertebral discs, pubic symphysis
secondary cartilaginous joints do what?
hold vertebrae together
how many IV discs are there?
23 (6C, 12T, 5L)
what is the contradictory fact for the IV discs?
contradicted by Palastanga et al. (2012) who say 24 in total with possible additional discs between fused sacral segments
discs increase or decrease in thickness down the vertebral column?
increase
what is the exception of thickness in the discs?
slightly narrow in upper thoracic region
what are the 3 distinct regions of the IV discs?
Central nucleus pulposus
Outer annulus fibrosis
Superior and inferior cartilagenous endplates
what is the structure of the nucleus pulposus?
Random arrangement of collagen fibres
Radially organised elastin fibres
Hydrated extracellular matrix containing aggrecan
what is the structure of the annulus fibrosus?
concentric layers od cartilage- lamellae, collagen type I and II fibres lying parallel within lamella- 60 degrees to the vertical axis
elastic fibres arranged between lamellae
cell morphology of the annulus fibrosus?
outer region- fibroblast- like, thin, elongated, parallel to collagen fibres
inner region- more oval
what are the IV specific features?
Cells possess cytoplasmic projections (30 micrometres or longer)
Reduced aggregation of aggrecan
Increased levels of glycosaminoglycans (keratan sulphate) instead of high levels of aggrecan
function of the nucleus pulposus?
Shock absorber
Even distribution of pressure across the disc
Components of extracellular matrix keep disc hydrated
function of annulus fibrosus?
Shock absorber
Tensile strength due to arrangement of collagen fibres
Lamina resists compressive forces
Disc able to return to original orientation due to elastin fibres
Anchorage of tissue to bone
Components of extracellular matric keep disc hydrated
what is the vertebral end plate?
Thickened layer of cortical bone
Superior and inferior surface of vertebrae
Flattened surface to allow attachment to intervertebral discs
what is the cartilagenous endplate?
Thin layer of hyaline cartilage
Between vertebral endplate and nucleus pulposus
Thickest on the outer edge
Thickness consistent along length of vertebral column - debate amongst literature about precise thickness (ranging from 0.1– 1.6 mm)
what type of cartilage is in the cartilaginous end plates?
hyaline
how are the collagen fibres arranged in the cartilaginous end plates?
arranged parallel to vertebral bodies and continue into intervertebral discs
what kind of layers are in the cartilaginous end plates?
calcified and uncalcified
are the cartilaginous end plates more hydrated or less hydrated than the nucleus pulposus and annulus fibrosus?
less hydrated
what kind of canals are in the cartilaginous end plates?
vascular canals
function of cartilaginous end plates?
- mechancial barrier
- support to neighbouring IV discs
- even distribution of load across intervertebral discs
- Anchors collagen fibres from in the intervertebral disc
- semi-permeable allows diffusion of nutrients from blood vessels to the discs
what is spondylosis?
Degenerative disease of the intervertebral discs resulting in stiff joints
Age-related wear and tear of the facet joint
spondylosis occurs with what?
Cartilage degeneration occurs with increased age
Chondrocyte hypertrophy and dysfunction – not yet known how chondrocytes are activated in a way to cause disease
Cartilage repair mechanisms are believed to play a part
Increased proteolytic enzymes degrading extracellular matrix and reducing hydration – secondary synovitis results and increased joint stiffness
what is the management for spondylosis?
No drugs to reverse process Symptomatic management Physiotherapy NSAIDs Surgery
what is Intervertebral Osteochondrosis ?
disc degeneration
Back pain caused by normal progression of changes occuring in the intervertebral disc with age
Dysfunction of end plates responsible for disc degeneration – agreement across literature
what are the Pathological changes of Intervertebral Osteochondrosis?
Nucleus pulposus becomes more fibrotic and less organised with increased age
Annulus fibrosus becomes disorganised – irregular lamellae
Formation of clefts and fissures in the discs
Ectopic calcification occludes vascular canals which disrupts nutrient transport to disc – study 4 demonstrates the link between occluded vascular canals, degenerated discs and ageing, from histological samples
Decreased glycosaminoglycans
diagnosis for Intervertebral Osteochondrosis?
MRI
management for Intervertebral Osteochondrosis ?
Physiotherapy
NSAIDs
Steroid injections
Surgery
complications of Intervertebral Osteochondrosis ?
Sciatica
Disc herniation
Disc prolapse
what is Uncovertebral Arthrosis?
Uncinate process of the vertebrae is a hooked projection on the superior surface of the vertebral body
Uncovertebral arthrosis is osteoarthritis specific to this joint – considered to be a complication of cervical osteoarthritis (not a lot of literature on this topic)
where is Uncovertebral Arthrosis usually found?
Found in the cervical region of the vertebral column
what is Uncovertebral Arthrosis more commonly known as ?
Luschka’s joint
