Cartilage Flashcards
What cells are present in the cartilage connective tissues?
Fibroblasts
Adipose cells
Osteocytes
Chondrocytes
What is present in the ECM of cartilage?
Fibres (collagen, reticular or elastic)
Ground substance (GAGs and glycoproteins)
Tissue fluid
What is the reference for the general constituents of cartilage?
Kerr, 2010
What is cartilage surrounded by? What is its structure?
Perichondrium:
- Dense, irregular connective tissue
- Composed largely of collagen
What are the general functions of cartilage?
Supportive framework of organs
Articulate surfaces
Forms most of foetal skeleton (largely replaced by bone)
What cells form cartilage and what is it surrounded by?
Chondrocytes surrounded by specialised ECM
What is the outer layer of perichondrium and what is it composed of?
Fibrous outer layer composed of:
- Fibroblasts
- Collagen fibres
What is the inner layer of perichondrium and what is it composed of?
Chondrogenic inner layer:
- Chondroblasts
- Chondrogenic cells (produce new chondroblasts)
What is the reference for general cartilage structure, perichondrium and chondrocytes?
Gartner and Hiatt, 2014
What is the space that individual chondrocytes are found within?
A lacuna
What is an isogenous group?
When a chondrocytes divides there may be more than one chondrocytes within the lacuna
What is the typical shape of a chondrocyte?
Egg-shaped
What is the function of chondrocytes?
Produce and maintain ECM
How much of cartilage is made up of ECM?
> 95%
What are the predominant components of the cartilage ECM?
Type II collagen
Proteoglycan aggregates
How does the high degree of hydration of the cartilage ECM affect its function?
It means cartilage can respond to varying loads
How is nutrition supplied to the ECM?
Diffusion between blood vessels in:
- Perichondrium
- Chondrocytes
What is the matrix immediately surrounding a chondrocyte?
Capsular matrix
What is the territorial matrix?
Darker matrix immediately around lacunae of isogenous groups
What is the lighter ECM that composes the rest of the ECM?
Interterritorial matrix
What are the references for the ECM?
Ross and Pawlina, 2006
Kerr, 2010
How do chondrocytes develop?
Mesenchymal embryonic cells differentiate into chondroblasts
Chondroblasts secrete cartilage matrix
Matrix surrounds Chondroblasts = Chondrocytes in lacunae
Describe interstitial cartilage growth?
Growth from a number of centres
Chondroblasts multiply and divide into clusters of cells = Isogenous groups
Groups produce ECM which separates Chondroblasts = Chondrocytes
In what type of cartilage does interstitial growth occur?
Immature
What is appositional cartilage growth?
Growth through addition of new layers to existing ones
Occurs in chondrogenic layer of perichondrium
In what type of cartilage does appositional growth occur?
Mature cartilage
What is the reference for cartilage growth?
Gartner and Hiatt, 2014
What are the components of hyaline cartilage?
Chondrocytes
ECM:
- Predominantly Type II collagen
- Chondroitin sulfate
What are the functions of hyaline cartilage?
Low friction surface via lubrication of synovial joints
Distributes forces to underlying bone
Where is hyaline cartilage found?
Articulate surfaces of synovial joints
Foetal skeleton - Provides model for its development
Costal cartilage - Some passive movement
What are the components of fibrocartilage?
Chondrocytes ECM: - Type I collagen fibrils (connective tissue matrix) - Type II collagen fibrils (hyaline) Dense regular connective tissue
Why is there less matrix associated with chondrocytes in fibrocartilage?
Chondrocytes are dispersed amongst collagen fibres
Does fibrocartilage have a perichondrium?
No
What shape is the nucleus of chondrocytes in fibrocartilage?
Rounded
What is the shape of the nucleus of fibroblasts in fibrocartilage?
Flattened and elongated
What are the functions of fibrocartilage?
Shock-absorption
Flexibility
Deformation resistance
Where is fibrocartilage found?
Secondary cartilaginous joints (symphyses):
- IV discs
- Pubic symphysis
What is a useful reference for both hyaline cartilage and fibrocartilage?
Ross and Pawlina, 2006
What are the components of elastic cartilage?
Chondrocytes ECM: - Type II collagen - Proteoglycans - Elastin (elastic fibres and interconnecting elastic sheets)
Which types of cartilage calcify with age?
Hyaline
Where is elastic cartilage found?
Pinna
Pharyngotympanic (eustachian) tube
What cartilages are present in the vertebral column?
Hyaline: - Zygapophyseal joints - Cartilagenous end plates Fibrocartilage: - IV discs
What directions do the facet joints in the cervical, thoracic and lumbar regions allow movement in?
Cervical: - All directions Thoracic: - Lateral Flexion - Rotation Lumbar: - Flexion - Extension - Lateral flexion
What is the role of hyaline cartilage on the facet joints?
Reduces friction
In what direction does the thickness of the IV discs increase?
Craniocaudally
What is the composition of the IV discs?
Mostly ECM
Only ~1% volume chondrocytes
IV discs are the largest non-vascular structures in the body. How much distance is there between some lumbar discs and direct blood supply?
20mm
What types of collagen does the nucleus pulposus produce?
Type II
What types of collagen does the annulus fibrosus produce?
Type I
Type II
What are the functions of the IV discs?
Shock absorption
Flexibility
Transmission of load
From what do the cartilaginous endplates develop from?
Mesoderm
How much of the IV space do the cartilaginous end plates make up?
~5% of adult IV space
~50% at birth
At birth there are vascular channels running through end plates, how do these change throughout life and how does this affect function?
Fill with ECM by end of first decade of life
Provide nutrition to IV disc
What are the functions of the cartilaginous end plates?
Growth plate for vertebrae in early life
Nutrient transport to IV disc
Barrier between VB and nucleus pulposus preventing Schmorl’s nodes
What can arise if the IV discs degenerate?
Intervertebral osteochondrosis
How does intervertebral osteochondrosis initially begin?
As a Schmorl’s node:
- Herniation of nucleus pulposus through cartilaginous and bony endplates into adjacent vertebral body
Where is intervertebral osteochondrosis most common?
Cervical region
Lower lumbar region
How does intervertebral osteochondrosis appear radiographically?
Loss of disc space
Bony sclerosis of vertebral bodies
If intervertebral osteochondrosis progresses, what can it result in?
Destruction of cartilaginous endplate
Bulging of outer fibres of annulus fibrosus
What is osteoarthritis?
A non-infective arthritis affecting synovial joints
Degeneration of articulate cartilage through reduced proteoglycan content in ECM
What are the pathological features of osteoarthritis?
Loss of joint space
Osteophyte growth at joint margins
Subchondral sclerosis
(Subchondral cysts)
What is the only synovial joint in the spine affected by osteoarthritis?
Zygapophyseal joints
What is the sequelae of uncovertebral joint degeneration in the cervical spine?
Osteophyte formation
Stenosis of IV foramina
Vertebral artery compression
What are the costal articulations with the spine?
Costovertebral
Costotransverse
Where is degeneration in the thoracic spine common?
Between T11 and T12 with ribs 11 and 12 respectively
What happens in SIJ degeneration?
Complete or partial joint ankylosis:
- Stiffening and hardening of joint
- Stiffness and reduced range of movement of joint
Osteophytes on anterior articular surface
Bony sclerosis on anterior articular surface
