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− | <big><center>[[Bones|'''BACK TO BONES''']]</center></big>
| + | ==Changes to normal structure== |
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| + | ===Damage to Periosteum=== |
| + | *Invokes a hyperplastic reaction of the inner layer |
| + | *Is painful |
| + | *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]]) |
− | ===Normal structure===
| + | *Longitudinal bone growth results |
− | [[Image:Bone micro structure.jpg|right|thumb|100px|<small><center>Microscopic bone (Courtesy of RVC Histology images)</center></small>]]
| + | *May be only on one side where periosteum is damaged |
− | | + | **Used by surgeons to treat [[Angular Limb Deformity|angular limb deformities]] |
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− | ===Periosteum and blood supply===
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− | *'''Periosteum'''
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− | **Specialised sheath of connective tissue covering bone except at the articular surfaces
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− | **Loosely attached except at tendon insertions and boney prominences (associated with major blood vessels penetrating bone)
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− | **Histologically:
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− | ***Outer layer - fibrous for support
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− | ***Inner layer - osteogenic
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− | ****Contains osteoblasts and osteoprogenitor stem cells in young animals and in adults with fractures or disease
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− | **Rich supply of nerves and lymph vessels
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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:
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− | ***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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− | *'''Blood vessels'''
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− | **Nutrient, metaphyseal, periosteal arteries
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− | **Normal flow of blood from medulla to periosteum due to higher pressures in medulla
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− | **Young animals have greater blood supply
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− | *'''Endosteum''' lines the marrow cavity
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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===
| + | [[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>
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