Catilage Flashcards
3 types of cartilage
Hyaline
Elastic
Fibrocartilage
2 things in common with all types of cartilage
- all have matrix containing proteolytic and hyaluronic acid
- all have chondrocytes
What does the matrix of hyaline cartilage contain?
Type II collagen - hyaluronate proteoglycan aggregates bound to the fine collagen matrix fibres
Contains fluid so gives compressability and collagen 2 thinner so more flexible
What does the matrix of elastic cartilage contain?
elastic fibres and type II collagen in elastic lamellae (layers) with chondrocytes sat loosely on top to allow recoil - tough but flexible
What does the matrix of fibrocartilage contain?
Mainly type I collagen fibres but some type II collagen fibres - very tough cartilage
Cell type found in hyaline cartilage and how they are found
Chondrocytes - found present alone, or if recently divided in small clusters called isogenous groups
What are isogenous groups of chondrocytes?
Chondrocytes all generated from the same chondroblast and they separate as they lay down extracellular matrix between them
What is hyaline cartilage important for in fetal development?
It is the precursor model of the bones that develop by endochondral ossification
What type of extracellular matrix is in hyaline cartilage? Why is this useful?
Avascular (no blood vessels) in which chondrocytes lie and this loose matrix allows diffusion of materials like nutrients and oxygen
Solid and firm but also pliable due to high water content so resilient to repeated application of pressure
What cells produce the extracellular matrix in cartilage?
Chondrocytes lay down matrix within the cell as vesicles
How does hyaluronic acid help in hyaline cartilage?
It drags water into the cartilage so assists resilience to repeated application of pressure
What happens to chondrocytes when placed under pressure in cartilage?
Mechanical signals increase synthetic activity (releases more collagen to assist) to release the pressure
What is secreted into spaces between chondrocytes and why/
Fibres and GAGs/hyaluronic acid to aid tissue expansion
Where will you find hyaline cartilage?
In all articulated joints
Nose
Larynx
Tracheal wall
What covers the margin of hyaline cartilage?
Perichondrium
What is the role of the perichondrium in hyaline cartilage?
Feeds in chondroblasts from both sides of cartilage which develop into chondrocytes. As the isogenous groups expand they force the 2 sides of perichondrium apart- leading to interstitial growth
Where do chondrocytes sit within the cartilage?
Lacuna
Role of cartilage in tracheal wall
Reinforces trachea and keeps airway open
What happens in adults if the cartilage is damaged at articular surfaces? (2)
In an adult the cells dont proliferate enough to repair the damage so the fibroblasts lay down scar tissue instead and there is a loss of flexibility
Fragments of cartilage can also lie in the joint and become calcified, leading to loss of flexibility
What are osteophytes?
Bony spurs associated with the degeneration of cartilage at joints
Calcified with age
Cell type present in elastic cartilage
Chondrocyte (no other cell types present)
Where is elastic cartilage found in the body (3)
Pinna of the ear
Eustachian tube
Epiglottis on top of trachea (allows food to go down oesophagus and air down trachea)
Cell types found in fibrocartilage
Chondrocytes and fibroblasts
Cells often distributed in rows
What is fibrocartilage made up of?
Combination of dense regular connective tissue and hyaline cartilage
What structures does fibrocartilage not contain?
Perichondrium
Where is fibrocartilage present?
Intervertebral discs
Articular discs fo sternoclavicular and temporomandibular joints
Menesci of the knee joint
Pubic symphysis
What is the role of the fibrocartilage?
Act as a shock absorber and to resist shearing forces - prevents bones being pulled apart
How are chondrocytes arranged?
Arranged in rows or as isogenous groups
Why is fibrocartilage shown in different directions in histology?
Shows that movement can be allowed in different directions
How does hyaline cartilage help with bone formation?
Used as a template for long bones by endochondral ossification
Starts as collagen II then subsequently turned to collagen I and then calcified to form bone
How is the epiphyseal growth plate aided by cartilage?
Columns of calcified cartilage extend from the growth plate and become mineralised to form bone - this extends the bone
5 zones of cartilage in epiphyseal growth plate
Zone of reserve cartilage - no proliferation or matrix production
Zone of proliferation - cells divide into columns, enlarge and secrete matrix
Zone of hypertrophy - cell enlarge and matrix compressed into linear bands between cell columns
Zone of calcified cartilage - enlarged cells degenerate and matrix calcifies
Zone of reabsorption - calcified matrix in contact with marrow; blood vessels and connective tissue invade region occupied by dying chondrocytes, leaving calcified cartilage spicules between them. Bone is laid down on these spicules.
Describe a growing bone spicule
Osteoblasts surround spicule and deposit new osteoid to be mineralised - become osteocyte once surrounded by new osteoid
2 most common cartilage/bone diseases
Osteoarthritis
Rheumatoid arthritis
What is osteoarthritis?
degenerative joint disease
Mechanical failure of articular cartilage - narrowing of joint space so bone rubs against bone
What is rheumatoid arthritis?
Autoimmune disease causing inflammation of synovial membrane and thickening of joint capsule
This causes damage to underlying bone and then the cartilage causing both bone and cartilage degeneration
How does a normal knee joint prevent joint pain?
How does a normal knee joint prevent joint pain?
How does a normal knee joint prevent joint pain?
Degeneration of cartilage narrows the joint space
This can lead to growth of osteophytes (bony spurs) - they can fuse to other bone, causing inflammation and pain
