L2 Cartilage and Endochondrial Ossification Flashcards
what are the three functions of cartilage?
support where flexibility required
shock abs
smooth articular surfaces
what cell is present in cartilage
chondrocytes , encased in lacunae
if lacunae containing chondrocytes are packed closely together what does this mean? what is the term for this ?
- proliferation has been recent
“interstitial growth”
what is the extracellular matrix composed of?
- type II collagen
- amorphous extracellular material
what is the amorphous extracellular material within the cartilage matrix composed of?
- proteoglycans and hyaluronan
- proteoglycan = core protein w/ side chain of sulphated glycosaminoglycan (GAG)
- hyaluronan = non sulphated GAG
explain why cartilage is highly resistant to compression?
- GAGs within the amorphous extra cell material of the matrix have multiple -ve charge therefore are strongly HYDROPHILIC = draws water
- swelling pressure of hydrophilic prtoeglycan aggregates counteracted w/ tension of collagen II fibres = high resistance to compression
what are the three types of cartilage?
- hyaline
- elastic
- fibrocartilage
where can hyaline cartilage be found?
- resp tract (cricoid cart in larynx, trachea, bronchi)
- ventral ends of the ribs
- articular cartilage
- growth plates
in all locations except for ________ and _______, hyaline cartilage has a _________.
a) articular surface cartilage
b) growth plate
c) PERICHONDRIUM
hyaline cartilage has a high/low ratio of GAGs:collagen
HIGH
cells are arranged randomly/organised within hyaline cartilage
RANDOMLY except for in growth plates = cells arranged in columns
elastic cartilage can be found in?
- external ear
- epiglottis
what kind of fibres are found within the matrix of elastic cartilage?
lastic fibres
does elastic cartilage have a perichondrium?
YA
fibrocartilage can be found in?
- intervertebral discs
- cardiac skeleton
fibrocartilage has a high/low ration of GAGs:collagen
LOW
does fibrocartilage have a perichondrium?
NO
chondrocytes are arranged randomly/organised in fibrocartilage?
ORGANISED - arranged in lines b/w bundles of fibre
describe the stepwise process of endochondral ossification ie/ hypertrophy, invasion, resporption
- begin w/ formation of cartilage model
- HYPERTROPHY of chondrocytes
- formation of periosteal been collar (some mesenchymal cells diff into osteoblast and secrete bone)
- INVASION of cartilage by blood vessel, osteoblast, bone marrow precursor
- RESORPTION of CARTILAGE by osteoclast
- DEPOSITON of bone on cartilage remnants by osteoblast
the site where ossification begins is known as the
primary centre for ossification
long bones have a primary centre of ossification and most also have a ______
secondary centre of ossification
hypertrophy of chondrocytes begins in which region of one?
mid-diaphysis
primary trabecular in the mid shaft region is resorbed to allow space for what?
the bone marrow
what factors regulate proliferation of chondrocytes for endochondral ossification?
- Growth hormone acting through insulin-like-growth factor (IGF-1) secreted from liver and locally by chondrocyte
- bone morphogenetic proteins (BMP)
- inhibited by signalling through fibroblast growth factor receptor 3 (FGF)
what factors regulate cartilage matrix secretion?
- IGF1
- BMPs
what factors regulate hypertrophy?
- stimulated through thyroid hormones acting through release by chondrocyte IGFs and FGFs, and suppression of parathyroid hormone-related peptide (PTHrP)
what factors regulate the invading cells ie/ blood vessels
- vascular endothelial growth factor VEGF stim angiogenesis
- BMPs stim osteoblast diff
- RANKL stimm osteoclast diff
defective regulation of behavioural growth plate chondrocytes is a result of mutation in genes encoding what?
- cartilage matrix proteins
- hormones, or growth factors regulating endochondrial ossification OR their receptors, intracell mediators of their effects
what are two examples of mutations of genes encoding endochondrial ossification?
- mutation of aggrecan gene responsible for bulldog dwarfism (chondrodysplasia) in dexter cattle
- IGF-1 allele major determinant of small size in dogs
