Cartilage and Endochondral Ossification Flashcards
What is a chondrocyte and its role?
Role = produce and maintain extracellular matrix
Each lies in a lacuna, loading = activity, deep in cartilage, give rise to isogenous groups = interstitial growth
Where is a chondroblast found and what does it do?
in perichondrium (lining), allows growth from periphery = appositional growth
Name the lining around cartilage
Perichondrium lines cartilage, not on articulated surfaces, contains fibroblasts-like cells, can diff into chondrocytes
What is the structure of hyaline cartilage?
proteoglycans + hyaluronic acid bound to fine collagen matrix + collagen II fibres, lined by perichondrium
Which cartilage type does not calcify?
elastic
Which cartilage gives shape and support?
elastic
Where is fibrous cartilage found?
disks, pubic synthesis (areas of high pressure), present at enthuses (point of attachment of tendon + bone)
Where is elastic cartilage found?
pinna (inner ear), epiglottis
How does hyaline cartilage relate to foetal bone development?
In the foetal skeleton hyaline cartilage is the precursor model of those bones which develop by endochondral ossification.
In which cartilage will you find flat fibroblasts?
fibrous
What is the function of hyaline cartilage?
Reduces friction, absorb shock
What type of tissue is cartilage?
Connective
The cartilage matrix has a large ratio of what?
Large ratio of glycosaminoglycan’s (GAGs) to type II collagen = diffusion of substances between chondrocytes + blood vessels. GAGs = high density –ve charges = attract water = hydrated gel
What does ossification mean?
formation of bone
What is the structure of elastic cartilage?
matrix like hyaline, addition of elastic fibres + elastic lamellae = elasticity, lined by perichondrium
What is the structure of fibrous cartilage?
matrix like hyaline, abundant collagen I fibres = combination of dense regular connective tissue + hyaline cartilage, NO PERICHONDRIUM
What does the word metaphysis mean?
columns of calcified cartilage extend from the growth plate and become mineralised
What is the difference between epiphysis and diaphysis?
Epiphysis –> end part of a long bone, initially growing separately from the shaft, Diaphysis –> shaft or central part of a long bone
Describe a synovial joint
movable joint, juxtaposed bone ends are covered by hyaline or fibrous, lie within synovial fluid bound by articular capsule lined by synovial membrane (macrophages removes debris from space, fibroblast-like cells = secrete synovial fluid)
Describe endochondral ossification
- Collar of periosteal bone appears in shaft,
- Nutrient arteries penetrate, supplying bone-depositing osteogenic cells – primary ossification centre formed,
- Medulla becomes cancellous bone, cartilage forms epiphyseal growth plates. Epiphyses develop secondary centres of ossification
- Epiphyses ossify, growth plates move apart lengthening bone,
- Epiphyseal growth plates replaced by bone. Hyaline articular cartilage persists
In what space does it chondrocytes lie?
Lacuna
What type of tissue is perichondrium?
Dense connective tissue
What is cartilage growth from the periphery know as?
Appositional growth
What is perichondrium?
Dense connective tissue that envelops hyaline and elastic cartilage where it is not at a joint
What is a GAG?`
Glycosaminoglycan - connected to proteoglycan - connected to hyaluronic acid. High density of -ve charge on GAGs = attracts water = forms hydrating gel in the cartilage matrix = allows withstanding of pressure
What is hyaluronic acid?
Makes up the gel in the extracellular matrix - assists resilience of repeated application of pressure
What does a large ratio of GAGs to type II collagen in cartilage permit?
Ready diffusion between chondrocytes and blood vessels surrounding cartilage
Does cartilage have blood vessels?
No
What fibres don’t calcify?
Elastic
What is deposition of further matrix by isogenous groups deep in the matrix called?
Interstitial growth
Outline: structure, function, placement and cell type for hyaline cartilage
STRUCTURE: GAGs - proteoglycans - hyaluronic acid, collagen II. FUNCTION: reduce friction, absorb shock. PLACEMENT: trachea, bronchi, articulating ends of bones. CELL TYPE: chondrocytes
Outline: structure, function, placement and cell type for elastic cartilage
STRUCTURE: like hyaline + elastic fibres. FUNCTION: shape and support. PLACEMENT: pinna (ear), epiglottis. CELL TYPE: chondrocytes
Outline: structure, function, placement and cell type for fibrous cartilage
STRUCTURE: like hyaline + collagen I. FUNCTION: withstand high pressure. PLACEMENT: disks, meniscus of knee joint, pubic symphysis. CELL TYPE: fibroblasts
What are the 2 types of cartilage growth and how are they different?
Appositional growth = THICKENING = growth from outside by chondroblasts from the perichondrium.
Interstitial growth = LENGTHENING = growth from the inside by chondrocytes that have differentiated into isogenous groups
