Difference between revisions of "Bone Response to Damage"

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<big><center>[[Bones|'''BACK TO BONES''']]</center></big>
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==Changes to normal structure==
  
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===Damage to Periosteum===
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*Invokes a hyperplastic reaction of the inner layer
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*Is painful
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*Exostoses can remodel or remain
  
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Lifting of periosteum causes new bone formation below
  
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Circumferential incision (e.g. during [[Bones Fractures - Pathology|fracture]])
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===Normal structure===
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*Longitudinal bone growth results
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*May be only on one side where periosteum is damaged
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**Damage to periosteum:
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**Used by surgeons to treat [[Angular Limb Deformity|angular limb deformities]]
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***Invokes a hyperplastic reaction of the inner layer
 
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***Is painful
 
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***Exostoses can remodel or remain
 
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**Lifting of periosteum causes new bone formation below
 
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**Circumferential incision (e.g. during [[Bones - fractures|fracture]])
 
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***Longitudinal bone growth results
 
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***May be only on one side where periosteum is damaged
 
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****Used by surgeons to treat [[Bones - developmental#Angular limb deformity|angular limb deformities]]
 
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===Bone development===
 
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*Two main types of bone development:
 
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**'''Endochondral ossification''' (cartilage model)
 
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***Long bones mainly - physis and metaphysis
 
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***Mesenchymal cells differentiate into chondroblasts
 
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****Produce scaffold of mineralised cartilage on which osteoblasts deposit bone
 
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***Vascularised
 
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***Developed centres of ossification
 
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****Primary (diaphyseal)
 
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****Secondary (epiphyseal)
 
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**'''Intramembranous ossification'''
 
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***Flat bones mainly (e.g. skull), shaft of long bones
 
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***Mesenchymal cells differentiate into osteoblasts
 
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***No cartilage precursor template
 
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===Physis (Growth plate)===
 
===Physis (Growth plate)===
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[[Image:Growth plate.jpg|left|thumb|100px|<small><center>Growth plate (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 
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[[Image:Growth plate closer.jpg|right|thumb|100px|<small><center>Growth plate magnified(Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 
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*Originates from the cartilage model that remains only at the junction of the diaphyseal and epiphyseal centres
 
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*Cartilage of metaphyseal growth plate is divided into: (from right to left on the magnified image)
 
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** - Resting (reserve) zone
 
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** - Proliferative zone
 
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** - Hypertrophic zone
 
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*Site of many '''congenital''' or '''nutritional''' bone diseases in the growing animal
 
*Site of many '''congenital''' or '''nutritional''' bone diseases in the growing animal
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*If growth teporarily stops -> layer of bone seals the growth plate -> moves into metaphysis when growth resumes -> forms '''Harris lines'''
 
*If growth teporarily stops -> layer of bone seals the growth plate -> moves into metaphysis when growth resumes -> forms '''Harris lines'''
  
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==Test yourself with the Bone and Cartilage Pathology Flashcards==
  
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[[Bones_and_Cartilage_Flashcards_-_Pathology|Bones and Cartilage Flashcards]]
  
  
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===Bone resorption===
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[[Category:Bones - Pathology|A]]
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*Mediated by two [[Parathyroid Pathology#Hormonal Control|hormones]]:
 
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**'''Parathyroid hormone (PTH)'''
 
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***Produced by <u>chief cells in the parathyroid glands</u> in response to <u>decreased</u> serum calcium
 
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***In response, osteoclasts increase in number and resorb mineralised matrix - increase Ca in blood
 
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**'''Calcitonin'''
 
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***Produced by <u>C-cells in the thyroid glands</u> in response to <u>increased</u> serum calcium
 
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***Inhibits osteoclasts
 
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===Bone dynamics===
 
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*Bone growth and maintenance of normal structure are directly related to mechanical forces
 
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*Mechanical forces generate bioelectrical potentials (piezoelectricity)
 
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**These potentials strengthen bone
 
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**Inactivity reduces the potentials -> bone loss
 
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*In neonates:
 
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**Bone growth predominates
 
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**Modelling is important
 
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*In adults:
 
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**Formation of bone is balanced by resorption - remodelling
 
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**Continues throughout life under the influence of hormones and mechanical pressure
 
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**Bone resorption may exceed formation in pathological states (hormonal, trauma, nutritional) or in old age and disuse
 
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<big><center>[[Bones|'''BACK TO BONES''']]</center></big>
 

Latest revision as of 12:39, 3 March 2011

Changes to normal structure

Damage to Periosteum

  • Invokes a hyperplastic reaction of the inner layer
  • Is painful
  • Exostoses can remodel or remain

Lifting of periosteum causes new bone formation below

Circumferential incision (e.g. during fracture)

  • Longitudinal bone growth results
  • May be only on one side where periosteum is damaged

Physis (Growth plate)

  • Site of many congenital or nutritional bone diseases in the growing animal
  • Open in neonates and growing animals
    • Chondrocyte proliferation balances cell maturation and death
  • Closes and ossifies at maturity
    • Regulated by androgens
  • If growth teporarily stops -> layer of bone seals the growth plate -> moves into metaphysis when growth resumes -> forms Harris lines

Test yourself with the Bone and Cartilage Pathology Flashcards

Bones and Cartilage Flashcards

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