PSL201Y1 Study Guide - Final Guide: Thyroglobulin

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8 Mar 2011
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LECTURE NINE: GROWTH CONTROL OF HORMONES
*growth {takes place during development} is different from remodelling {takes place constantly}
BONE GROWTH
STAGE
Mechanism
Other Considerations
1
- chondrocytes form a growth plate
chondrocytes are collagen producing cells of cartilage
2
- osteoblasts differentiate at the site of growth plate to start
ossification
ossification is activated by osteoblast differentiation
growth is dependent on:
Ædiet (malnutrition leads to a reduction of growth) Ægenetics
Æclassical hormones and growth factors
::growth hormone, thyroid hormone, insulin {are needed to activate
endocrine system and stimulate growth}
::sex steroids
::cortisol
::insulin-like growth factor (IGF-1)
Ægrowth hormone stimulates bone growth via direct and indirect binding
::indirect stimulation
Æbind to liver and trigger the release of IGF-1 {made from the liver}
ÆIGF-1 acts at matrix level recruiting chondrocytes
Æfavours chondrocytes proliferation
Æresults in proliferation of the matrix
Æosteoblasts will come and initiate ossification
::direct stimulation
Æbinding at the bone matrix
Ærecruits chondrocytes to the site of GH binding
Æleads to proliferation of chondrocytes
Æresults in enhancement of matrix growth
*chondrocytes result in increased (recruitment, proliferation, matrix)
Ægrowth hormone stimulates bone remodelling via direct and indirect binding of IGF-1
Æremodelling occurs every ~100 days
Æinvolves osteoClasts and osteoblasts
((bone remodelling))
Æfirst: recruitment of osteoclasts to site for matrix resorption/bone engulfment to create cavities
Ænext: recruitment of osteoblasts to proliferate and replace bone matrix {chewed up by osteoclasts}
\ÆGH and IGF-1 can directly recruit osteoblasts for bone replacement
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Document Summary

*growth {takes place during development} is different from remodelling {takes place constantly} Osteoblasts differentiate at the site of growth plate to start. S chondrocytes are collagen producing cells of cartilage. S ossification is activated by osteoblast differentiation ossification. diet (malnutrition leads to a reduction of growth) ::growth hormone, thyroid hormone, insulin {are needed to activate endocrine system and stimulate growth} growth hormone stimulates bone growth via direct and indirect binding. bind to liver and trigger the release of igf-1 {made from the liver} growth hormone stimulates bone remodelling via direct and indirect binding of igf-1. first: recruitment of osteoclasts to site for matrix resorption/bone engulfment to create cavities. next: recruitment of osteoblasts to proliferate and replace bone matrix {chewed up by osteoclasts} \gh and igf-1 can directly recruit osteoblasts for bone replacement. recruits chondrocytes to the site of gh binding. peptide hormone single chain polypeptide (~190 aas)

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