Cartilage Flashcards
What are the three types of joints that exist in the human body?
fibrous, cartilaginous, synovial
what are the 3 types of cartilage?
fibrous, elastic, hyaline articular
Describe fibrocartilage
➢ White, very tough material that provides high
tensile strength and support.
➢ Dense network of Type I collagen
➢ Contains more collagen and less proteoglycan than hyaline cartilage.
➢ Intervertebral discs, the symphysis pubis and the attachments of certain tendons and ligaments
Describe elastin cartilage
➢ Contains large amounts of elastic fibers (elastin)
scattered throughout the matrix.
➢ Stiff yet elastic, and is important to prevent tubular
structures from collapsing.
Describe hyaline articular cartilage
➢ Stiff, translucent material rich in Type II collagen and proteoglycan.
➢ Covers the end of bone to form the smooth
articular surface of joints
➢ Also found in the ear, the larynx and between the ribs and the sternum
What are the functions of hyaline articular cartilage?
Distribute joint loads over a wide area, decreasing stresses sustained by contacting joint surface
To allow relative movement of the opposing joint surfaces with minimal friction and wear
Devoid of blood vessels
Devoid of lymphatic vessels
Devoid of neurological input
What is the compostion of hyaline articular cartilage?
Dense ECM
Water, collagen, proteoglycans, non-collagenous proteins, glycoproteins, distribution of chondrocytes
Describe the composition of water in cartilage
➢ 80% of wet weight
~30% in interfibrillar collagen
~50% in matrix space
➢ Relative water concentration
80%: Superficial
65%: Deep zone
➢ Combination of frictional resistance to water flow and the pressurisation of water within matrix that gives cartilage its ability to withstand loads.
Describe the composition of collagen in cartilage
Collagens (forms fibrils)
➢ 60% of dry weight
➢ ~95% is Type II collagen
➢ ~Collagen Type (I, IV, V, VI, IX & XI
stabilise Type II)
Describe the composition of proteoglycans in cartilage
➢ 10-15% of wet weight
➢ Consist of core protein with 1 or
more linear glycosaminoglycan
chains covalently attached
Chains can consist of more than
100 monosaccharide’s
Remain unattached due to charge
➢ Many forms of PG
➢Aggrecan, decorin, biglycan &
fibromodulin
Describe the composition of chondrocytes in cartilage
Resident cells
➢ 2% of volume
➢ Unique role in development, maintenance and repair of
ECM
➢ Originate from MSCs
➢ Vary in shape and size depending on zone
What are the different zones in cartialge
thin superficial zone, middle transition zone, deep zone, tidemark
What does the thin superficial zone do?
What is its structure?
Protects deep layers form shear stresses
Responsible for most of the tensile strength
0-20%
Type 2 and IX
Packed tightly and parallel to surface
High number of flattened chondrocytes
What does the middle transitional zone do? what is its structure?
First line of resistance to compressive forces
0-60%
Proteoglycans
Thick cell II and IV
Organised obliquely
Low number and spehrical chondrocytes
What does the deep zone do? What is its structure?
Most of resistance to compressive forces
30%
Highest proteoglycans
Low water content
Low number of large spherical chondrocytes – columnar orientation
What does the tidemark layer do?
Calcified layer integral to adherence to bone
What are the roles of metabolism in cartilage?
nutrition supply: avascular nature of cartilage nutrition occurs through diffusion from the
synovial fluid.
-matrix restricts nutritional materials by size (pore size – 6nm), charge,
and molecular configuration.
Cartilage maintenance:
-Chondrocytes responsible for development, maintenance and repair of ECM via
enzymes
-Metabolic activity of chondrocytes dictated by mechanical loading and growth
factors
How does aging affect cartilage?
➢ Water content of cartilage increases
➢ Protein makeup degenerates
➢ Cartilage begins to degenerate by flaking or forming tiny crevasses. Overtime wears out resulting in bone on bone contact
Lack of lubrication = inflammation and icnreased stress = bone spur growth (osteophytes)
What are the three types of arthritis?
OA - very common, affects its exposed to high stresses – therefore considered the result of wear and tear
RA - autoimmune conditions that can result in loss of cartilage
Post-traumatic arthritis - after injury to the knee similar to OA
Can cartilage repair itself?
no limited self-repair capacity - damaged hyaline cartilage replaced by fibrocartilage scar tissue
Name three types of treatment used
Debridement, microfracture, mosaicplasty
What is athroplasty?
replacement of teh joint by a synthetic joint made of stainless steel alloy and HMWPE
