Cartilage & Bone Flashcards
Is cartilage avascular or vascular?
Avascular
Does cartilage contain nerves? Why or why not?
No - needs to withstand forces exerted on it in joints without pain or vascular damage
What type of collagen is abundant in cartilage?
Collagen type II - weaker than type I but imparts tensile strength
Cartilage is rich in a proteoglycan monomer called _____.
Aggrecan
What is aggrecan?
- Proteoglycan monomer
- Links to HA forming massive aggregates that avidly bind water
- Results in ECM that is 60-80% water
- Permits cartilage to withstand huge compressive forces and maintain overall volume even under pressure
What is the role of adhesive glycoproteins?
- Bind cells and components of the ECM together and to cell surfaces
- Have binding sites for collagen, GAGs, and integrins
What are chondrocytes?
- Cartilage cells
- Sparse and isolated in cartilage, surrounded by the ECM that they produce
- Produce and maintain fibres and organic components of the GS
- Metabolize glucose via anaerobic glycolysis since they are avascular
- Nourished via nutrient/gas diffusion through GS
- Mature cells tend to be found in isogenous groups
What are isogenous groups?
Daughter cells from a common precursor cell
Cartilage repairs _____.
Slowly
What is perichondrium?
Layer of CT that often surrounds cartilage and contains blood vessels, nerves, lymphatics, and aids in cartilage attachment and growth
What two layers does perichondrium consist of?
1) Fibrous layer with dense irregular CT consisting of fibroblasts and collagen type I; functions to provide attachment of cartilage to adjacent tissues
2) Inner cellular layer containing chondroblasts; functions to create organic components of cartilage ECM and contributes to cartilage growth
Describe the interstitial growth of cartilage.
- Growth from within
- Mesenchymal cells differentiate into chondroblasts, which secret organic components of ECM
- Chondroblasts surround themselves with matrix, move apart, and become isolated in their lacunae
- They may divide, forming isogenous cell groups, which secrete matrix and add to the thickness of developing cartilage
- Ultimately, isolated chondroblasts become dormant and maintain the matrix as chondrocytes
Describe the appositional growth of cartilage.
- Growth at the surface of newly-forming cartilage, rather than from its core
- Mesenchymal cells at the surface differentiate into fibroblasts, which secret collagen type I and form the fibrous layer of perichondrium
- Mesenchymal cells deep to the fibrous layer differentiate into chondroblasts, forming the cellular layer of the perichondrium
- Thickness of cartilage increases
What are the three subtypes of cartilage?
1) Hyaline cartilage
2) Elastic cartilage
3) Fibrocartilage
What is hyaline cartilage?
- Most common, weakest type of cartilage
- Forms tracheal rings, laryngeal, nasal, costal, articulate cartilages
- Also forms fetal and immature skeleton, and epiphyseal growth plates
- Functions to resist compression and reduce friction between bony surfaces
All hyaline cartilage is surrounded by perichondrium except…
Articular cartilage - vessels and nerves of perichondrium would be damaged by friction
What is elastic cartilage?
- Higher proportion of elastic fibres compared to hyaline cartilage
- Cartilage has greater flexibility and resiliency (ability to snap back after deformation)
- Forms pinna of external ear, epiglottis, and pharyngotympanic tube
What is fibrocartilage?
- Has a lot of collagen type I fibres with little GS
- Resistive to compressive forces and tensile forces
- No perichondrium
- Forms the annulus fibrosis, pubic symphysis, intra-articular disks, and entheses
How can we tell the difference between fibrocartilage and dense regular CT?
- Fibrocartilage has rows of round chondrocytes embedded between collagen fibres
- Dense regular CT has fibroctyes that are flattened and scattered throughout tissue
What is the composition of bone matrix?
- 1/3 organic matter, called osteoid, which is mostly collagen type I with some GS, which imparts tensile strength and flexibility to bone
- 2/3 inorganic matter, including hydroxyapatite and other minerals that mineralize osteoid and impart compressional strength on bone tissue
What is the only type of bone cell not derived from osteoprogenitor cells?
Osteoclasts - derived from the macrophage-monocyte linage
Osteoprogenitor cells are _____ found on the _____ of bone.
Squamous cells; surfaces