Cartilage Flashcards
1
Q
What are connective tissues composed of?
A
Cells and a surrounding matrix
2
Q
Which cells comprise the cellular component of connective tissue?
A
- Fibroblasts
- Adipose cells
- Osteocytes
- Chondrocytes
3
Q
Which elements comprise the matrix of connective tissue?
A
- Fibres (collagen, reticular or elastic)
- Ground substance (GAGs and glyoproteins)
- Tissue fluid
4
Q
What type of connective tissue is cartilage and what is it surrounded by?
A
- Hard connective tissue
- Surrounded by a layer of dense irregular connective tissue composed largely of collagen, known as the perichondrium.
5
Q
What are the functions of cartilage?
A
- Supportive framework of organs
- Buffer at articular surfaces
- Forms the greater part of the fetal skeleton (largely replaced by bone)
6
Q
What are chondrocytes surrounded by?
A
Specialised extracellular matrix
7
Q
What are the components of the perichondrium?
A
- Fibrous outer layer - mostly fibroblasts and collagen fibres.
- Inner chondrogenic layer - chondroblasts and chondrogenic cells.
8
Q
Describe the structure and function of chondrocytes
A
- Resident cells in cartilage
- Found individually in spaces known as lacunae
- Typically egg-shaped but can also be round or flattened
- Produce and maintain matrix
9
Q
Describe the extracellular matrix (ECM)
A
- Functional and dominating element of cartilage (>95% of tissue).
- Composition of ECM differs depending on type of cartilage (hyaline, elastic or fibrocartilage).
- High degree of hydration in ECM allows cartilage to respond to carying loads.
- Has capsular matrix, territorial matrix and interterritorial matrix components.
10
Q
What is the extracellular matric comprised of?
A
Predominantly type 2 collagen and proteoglycan aggregate
11
Q
What are the functions of the extracellular matrix?
A
- Maintains viability of tissue by permitting diffusion of substances (nutrients) between blood bessels in the perichondrium and chondrocytes.
- High degree of hydration in matrix allows cartilage to respond to varying loads.
12
Q
Describe the capsular matrix
A
Immediately around the chondrocyte
13
Q
Describe the territorial matrix
A
Darker, immediately surrounds the lacunae of isogenous groups
14
Q
Describe the interterritorial matrix
A
Lighter, makes up the remainder of the ECM
15
Q
Describe the role of chondrocytes in development
A
- Mesenchymal (embryonic cells) differentiate into chondroblasts
- Chondroblasts secrete cartilage matrix.
- Cartilage matrix surrounds chondroblasts - chondrocytes are within lacunae.
- Chonsrocytes are essential in maintaining the ECM - responsible for interstitial or appositional growth.
16
Q
Describe interstitial growth of cartilage
A
- Growth from a number of centres.
- Chondroblasts multiply and divide to form clusters of cells - isogenous groups.
- Groups produce matrix which separates the chondroblasts and in turn, produces chondrocytes.
- Occurs in immature cartilage
17
Q
Describe appositional growth of cartilage
A
- Growth through addition of new layers of matrix to existing ones
- Occurs in the chondrogenic layer of perichondrium
- Occurs mainly in mature cartilage
18
Q
Describe hyaline cartilage
A
- Most widespread type of cartilage
- Components:
- chondrocytes
- extracellular matrix (predominantly type 2 collagen)
19
Q
What are the functions of hyaline cartilage?
A
- Creates a low-friction surface via lubrication of synovial joints
- Distributes forces to underlying bone
- Provides model for developing fetal skeleton
20
Q
Where is hyaline cartilage found?
A
- Articular surfaces of synovial joints
- Fetal skeleton
- Costal cartilage
21
Q
Describe fibrocartilage
A
- Comprised of:
- chondrocytes
- ECM
- dense regular connective tissue
- Chondrocytes dispersed among collagen fibres, similar to hyaline cartilage with less cartilage matrix material associated with them.
- No perichondrium
- Chondrocytes have a rounded nuclei, fibroblasts have a flattened, elongated nuclei.
- ECM is characterised by both type 1 collagen fibrils (connective tissue matrix) and type 2 collagen fibrils (hyaline cartilage)
22
Q
What is the function of fibrocartilage?
A
Fibrocartilage acts as a shock absorber
23
Q
Where is fibrocartilage found?
A
- Intervertebral disc
- Pubic symphysis
24
Q
Describe elastic cartilage
A
- Distinguished by the presence of elastin in the cartilage matrix.
- Same components as hyaline cartilage but with addition of dense network of elastic fibres and interconnecting elastic sheets.
- Gives cartilage elastic properties
- Does not calcify during the ageing process (unlike hyaline)
25
Where is elastic cartilage found?
External ear (pinna)
26
Which type of cartilage is found in the zygapophyseal (facet) joints?
Hyaline cartilage
27
Which type of cartilage is found in the intervertebral discs?
Fibrocartilage
28
Which type of cartilage is found in the cartilaginous end plate?
Hyaline cartilage
29
Describe the zygapophyseal (facet) joints
* Synovial joint found between the sueprior and inferior articular processes on adjacent vertebrae.
* Highly susceptible to osteoarthritis
* Orientated to enable specific movements for each vertebral region:
* Cervical - all directions
* Thoracic - prdominantly lateral bending and rotation
* Lumbar - flexion, extension and some lateral bending
30
What is the function of hyaline cartilage?
Hyaline cartilage reduces friction
31
Describe the intervertebral disc
* Fibrocartilage plate between two (hyaline) end plates.
* Increase in thickness craniocaudally.
* Mostly ECM with ~1% volume of chondrocytes.
* Largest non-vascularised structures in the human body
* Up to 20mm between direct blood supply in some lumber IV discs
* Nucleus pulposus - synthesise only type 2 collagen
* Annulus fibrosus - synthesise type 1 and type 2 collagen
32
What are the functions of the IV disc?
Provides flexibility and transmission of load
33
Describe the cartilaginous end plate
* Hyaline cartilage
* Develop from mesoderm
* At birth there are large vascular channels through end plates which fill with ECM by the end of the first decade of life - provide nutrition to disc.
34
What are the functions of the cartilaginous end plate?
* Growth plate for vertebrae in early life
* Nutrient transport into disc
* Barries between nucleus pulposus and vertebral body; prevents gelatinous nucleus pulposus bulging into vertebral body.
35
What results from degeneration of the cartilage of the intervertebral disc?
Intervertebral osteochondrosis
36
What results from degeneration of cartilage at the zygapophyseal joints?
Osteoarthritis
37
What is intervertebral osteochondrosis?
Degeneration of the IV disc (fibrocartilage)
38
Where does intervertebral osteochondrosis initiate?
Initially begins as a Schmorl's node
39
What is a Schmorl's node?
Herniation of the nucleus pulposus through the cartilaginous and bony end plates into the adjacent vertebral body
40
Where can intervertebral osteochondrosis occur?
* At any level of the spine
* Most commonly found in the cervical and lower lumbar regions
41
How is intervertebral osteochondrosis represented on a radiograph?
* Loss of disc space
* Bony sclerosis of vertebral bodies (sclerosis = abnormal hardening of tissue)
42
What results from progression of intervertebral osteochondrosis?
* Destruction of the cartilaginous end plates
* Bulging of the outer fibres of the annulus fibrosus
43
Describe osteoarthritis
* Form of non-infectious arthritis affecting the synovial joints
* Common with increasing age
* Degeneration of articular cartilage through reduction in proteoglycan content in the ECM.
* **Zygapophyseal** joint is the only synovial joint in the spine affected by osteoarthritis.
44
What results from osteoarthritis (degeneration of articular cartilage through reduction in proteoglycan content in the ECM)?
* Osteophyte growth at the joint margins (attempting to return stability to joint).
* Osteophyte - bony outgrowths (spurs)
* Loss of joint space
* Sclerosis
45
Describe degeneration in the cervical spine (specifically the uncovertebral joints of Luschka).
* Found at the posterolateral portions of the vertebral body
* Contribute to the anterior aspect of the intervertebral foramen
* Articular cartilage degeneration leads predominantly to osteophyte formation.
* Osteophyte formation leading to stenosis of the lateral recess and resulting in **compression of the vertebral artery**.
* stenosis = narrowing of a passageway
46
Describe degeneration in the thoracic spine (specifically in the costal articulations).
* Costal articulations:
* Costvertebral - head of rib and vertebral bodies
* Costotransverse - neck and tubercles of ribs and transverse processes of vertebrae.
* Degeneration commonly found between T11 and T12 with 11th and 12th ribs respectively.
* Similar features as seen in other joints:
* Space narrowing
* Presence of osteophytes
* Sclerosis
47
Describe degeneration in the lumbar spine (specifically in the sacroiliac joint).
* Abnormalities can be unilateral or bilateral
* Complete or partial ankylosis of joint
* Ankylosis = abnormal stiffening and hardening of joints resulting in stiffness of the joint
* Osteophytosis and bony sclerosis apparent on the anterior articular surface
