Cartilage Flashcards
What is cartilage?
An avascular connective tissue that consists of an extensive extracellular matrix in which lie chondrocytes.
What produces and maintains the extracellular matrix in cartilage?
Chondrocytes
Why is there a large ratio of glycosaminoglycans to type II collagen in the cartilage matrix?
Permits ready diffusion of substances between the chondrocytes and the blood vessels that surround the cartilage
What assists the resilience of cartilage to the repeated application of pressure?
Large amount of hyaluronic acid in the extracellular matrix
What does the high density of negative charges on the GAGs do?
Attracts water, forming a hydrated gel
What does hyaluronic acid together with its attached proteoglycan monomers form?
A hyaluronate proteoglycan aggregate
What are the three types of cartilage?
Hyaline, Elastic and Fibrocartilage
What does the matrix of hyaline cartilage consist of?
Proteoglycans, hyaluronic acid and type II collagen
What does the matrix of elastic cartilage consist of?
Has a matrix like hyaline cartilage but with the addition of many elastic fibres and elastic lamellae
What does the matrix of fibrocartilage consist of?
Has a matrix like hyaline cartilage but with the addition of abundant type I collagen fibres
What is the cell type found in hyaline cartilage?
Chondrocytes
What are isogenous groups?
Small clusters of recently divided chondrocytes
When do the chondrocytes within the isogenous groups seperate?
As they lay down the extracellular matrix
In early fetal development, hyaline cartilage is the precursor model of the bones which develop via which type of ossification?
Endochondral ossification
As long bones develop, where does some hyaline cartilage remain?
At the articulating surface and also at the epiphyseal plate until growth ceases
Where is hyaline cartilage found in the body?
Articulating surfaces, rib cage, trachea, bronchi and larynx
What is the perichondrium?
Dense irregular connective tissue that covers the margin of hyaline cartilage
What does the perichondrium contain?
Many elongated, fibroblast-like cells which can develop into chondroblasts and thereafter into chondrocytes
What is appositional growth of cartilage?
Fibroblasts in the perichondrium give rise to flat, newly formed chondroblasts which secrete matrix components and round up to develop into chondrocytes, resulting in cartilage growth.
The process of appositional growth occurs when the cartilage model also grows in thickness due to the addition of more extracellular matrix on the peripheral cartilage surface, which is accompanied by new chondroblasts that develop from the perichondrium.
What is interstitial growth of cartilage?
The cartilage model will grow in length by continuous cell division of chondrocytes, which is accompanied by further secretion of extracellular matrix. The cells of the isogenous groups separate as they lay down further matrix.
What is the lacunae in cartilage?
Spaces in which the chondrocytes lie
Where is there no perichondrium?
At articulating surfaces
What is the epiphyseal growth plate formed from?
Hyaline cartilage
Hyaline cartilage calcifies with ageing. What about elastic cartilage?
Elastic cartilage does not calcify
Where is elastic cartilage found in the body?
Pinna of the ear, epiglottis, Eustachian tube
How do elastin fibres stain?
Dark staining
What are the cell types present in fibrocartilage?
Chondrocytes and fibroblasts
What is fibrocatilage a combination of?
Dense regular connective tissue and hyaline cartilage
Does fibrocartilage have a perichondrium
No
Where is fibrocartilage found in the body?
Intervertebral discs, menisci of the knee joint and pubic symphysis
What does fibrocartilage act as?
Shock absorber
How are chondrocytes often arranged in fibrocartilage?
In rows or as isogenous groups
What is an enthesis?
Points of attachment of tendon and bone - fibrocartilage is often present
What is endochondral ossification?
Involves the replacement of a pre-existing hyaline cartilage template by bone. This is the way in which most bones develop.
What happens to the epiphyseal plate of long bones after the cessation of growth?
Disappears
How is the synthetic activity of the chondrocytes directed?
Pressure loads applied to the cartilage create mechanical, electcal and chemical signals that direct the synthetic activity of the chondrocytes
At which stage of embryonic development does a collar of periosteal bone appear in the shaft?
6-8 weeks
At which stage of development does central cartilage calcify and a nutrient artery penetrate to supply osteogenic cells?
8-12 weeks
At 8-12 weeks, central cartilage calcifies and a nutrient artery penetrates to supply osteogenic cells. What is formed?
Primary ossification centre
When does the medulla become cancellous bone and cartilage form epiphyseal growth plates?
Post-natal
After birth, what to epiphyses develop?
Secondary centres of ossification
When do epiphyses ossify and growth plates continue to move apart and lengthen bone?
Pre-pubertal
What is the final state of endochondral ossification?
Epiphyseal growth plates replaced by bone but hyaline articular cartilage persists
The bone increases in length via which type of ossificaition?
Endochondral ossification
The bone increases in girth (periosteal ossification) via which type of ossification?
Intramembranous ossification
What is the synovial joint?
A moveable joint in which the opposed bone ends are:
- Covered by hyaline cartilage or fibrocartilage
- Lie within lubricating synovial fluid bounded by an articular capsule which is lined by a synovial membrane and reinforced with fibrous tissue and ligaments
What does the synovial membrane consist of?
Macrophages and fibroblast-like cells which secrete the synovial fluid
What is the fibrous capsule continuous with?
The periosteum
Which type of connective tissue is the periosteum?
Dense CT
What are the 4 zones of an epiphyseal growth plate?
Zone of proliferation - cells actively dividing
Zone of hypertrophy - cells enlarge greatly
Zone of calcified cartilage - cells begin to degenerate and matrix calcifies
Zone of resorption - calcified matrix in direct contact with the marrow cavity
