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SKELETAL GROWTH + DEV (LO's: (Understand how bone forms with unique…
SKELETAL GROWTH + DEV
LO's:
Understand how bone forms with unique size, shape and anatomical identity.
Comprehend the distinctive processes by which bone grows.
Identify regulators of bone growth.
Embryonic origin (cell lineages)
Neural Crest (neuroectoderm)
Cranofacial Bones
Paraxial mesoderm
Axial skeleton
Lateral plate mesoderm
Limb skeleton
Limb bud
Apical ectodermal ridge
Essential for elongation of the limb
Progress zone
Zone of polarising activity
Factors affecting growth
Nutrition:
Vitamin C
Collogen synthesis
Vitamin D
Calcium absorption
Hormones;
Growth Hormone
Insulin growth factor
Thyroid hormones
Estrogen
Expressed at end of puberty
Effects bone growth negatively
Mechanical forces
Patterning
Embryonic growth
Positional
Ossification
Endochondral
Most frequent
Cartilage template
Forms long bones
Osteochondral > Chondrocytes
Steps:
Change in cell shape
Hypertrophy
Blood vessels invade
Forms bone
Primary ossification (before birth)
Secondary ossification (after birth)
Hypoxia attracts blood vessels
Intramembranous
Forms flat bone
Osteochondral > Osteoblasts
Has to be rich in blood vessels
Signalling molecules
Bone forming
TF:
Runx2
High beta-catenin
Cartilage forming
TF:
Sox9
Low beta-catenin
Diameter growth
Periosteal apposition
Deposition of a layer followed by resorption of previous layer
Bone accumulation
70% - 80% genetic
30% - 40% environmental
Common progenitor
Osteochondral progenitor
Positional Identity
Position of mesenchymal cells decide their fate