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23 Cards in this Set
- Front
- Back
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Circulation to Mature Bone
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Nutrient artery and vein
Metaphyseal vessels Periosteal vessels |
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Circulation to Mature Bone
Nutrient artery and vein |
Enter and exit the medullary cavity through the nutrient foramen
Nutrient foramen passes through cortex of bone shaft Some bones have multiple foramina |
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Circulation to Mature Bone
Metaphyseal vessels |
Supplies blood to the inner diaphseal surface of each epiphyseal plate (where cartilage is being replaced by bone)
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Circulation to Mature Bone
Periosteal vessels |
In the bone between the osteogenic layer (cells of periosteum) and calcified matrix (bone)
the give branches that become the vessels of the osteon in the cortex |
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Mineral Composition of Bone
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Organic compounds (collagen ) - 1/3
Inorganic components 2/3 - 39% calcium and 17% phosphate |
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Calcium metabolism
vitamin D |
7- Dehydrocholesterol is in the skin
When exposed to sun it becomes cholecalciferol (provitamin D3) vitamin D3 is transported to the liver and is changed to 25 hydroxycholecalciferol (this is an inactive form of provitamin D) It then travels to the kidney and is converted into 1, 25 dihydroxycholecalciferol 1, 25 dihydroxycholecalciferol is also called calcitriol which is an active form of vitamin D |
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Calcium metabolism
vitamin D |
Calcitriol travels to the intestinal mucosa where it stimulates the production of mRNA and a specific protein which is needed for calcium absorption
vitamin D is essential for calcium uptake Vitamin D is present in dairy |
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Calcium
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ionic calcium is needed for nerve impulses,muscle contraction, coagulation, cell division and glandular secretion
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Calcium
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Human body contains 1200-1400 g of calcium
99% of calcium is present in bone Represents 1.5% of body weight Most of calcium balance is within the body cells |
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Calcium
Blood Levels |
500mg of Calcium is present in blood
Blood calcium levels are 9-11mg/dl or 5meq/L A meq=mole/valence divided by 1000 40/2 = 20/1000 = 20mg/L So 5 meq = 5 x 20 = 100mg/L |
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Calcium
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455 of caclium is in a diffusible ionized form
Rest is non-diffusible and bound to a plasma protein When ionized calcium levels drop, it causes hypocalcemic tetany this is a result of electrical differences with Na channels staying open in muscles |
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Calcium Shifts
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During hyperventilation, pH increases
This causes calcium ions to bind to proteins Causes a decrease in blood calcium without a true deficiency but still see hypocalcemic tetany Treatment is to correct the pH - as Co2 levels increase, pH returns to normal |
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Calcium
Endocrine Influences |
Calcium ion homeostasis is maintained by a negative feedback system involving 2 hormones:
parathyroid hormone calcitonin ( a thyroid hormone) |
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Calcium
Endocrine influences |
3 tasrget sites
Bones - storage Digestive tract - absorption Kidneys - excretion parathyroid hormone increases blood caclium levels Calcitonin decreases blood calcium levels |
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Calcium
Endocrine influences Parathyroid hormone |
Increases osteoclast activity
Increases absorption Inhibits renal excretion |
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Calcium
Endocrine influences Calcitonin |
Increases calcium storage by bones by increasing osteoblastic activity
Inhibits osteoclastic activity Increases rate of renal excretion |
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Bone Growth and Maintenance
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see chart
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Fractures
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Bones can break or crack if subjected to severe stresses
Will heal if blood supply and cells of the endosteum and periosteum survive |
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Bone Repair
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Fracture hematoma - blood seeps in
Callus formation - cells from the intact endosteum and periosteum undergo rapid mitosis and migrate to the fracture zone; the cells form a callus of periosteum and cartilage that encircles the fracture zone |
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Bone Repair
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osteoblasts infiltrate the cartilage and the cartilage gives way to spongy bone (endochondral ossification)
Dead bone is removed and new bone is formed osteoblasts and osteoclasts replace and remodel the spongy bone The spongy bone of the cortical region is transformed into compact bone and the bone continues to remodel remodelling continues for 4 months to 1 year Site may may even be thicker after repair |
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Fractures
types |
closed - internal - can only be seen on xray
Open or compound fractures project through the skin |
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fractures
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Pott's fracture - ankle; affects both bones
Comminuted - shatters the bony into many fragments Transverse - breaks a bone shaft across its long axis Spiral - produced by twisting stresses Displaced - produce abnormal bone arrangements Colles - break in distal portion of radius Greenstick - only 1 side of the shaft is broken - typically in children Epiphyseal - at epiphyseal plate - must be treated or can stop growth Compression - in vertebrae |
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miscellaneous Clinical Considerations
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Osteoporosis - bone softening
Osteopenia - inadequate ossification Osteomalacia - calcium deficienct lyeading to soft bones Rickets - calcium deficiency in children Marfan's Syndrome - gentic; long slender appendages osteogenesis Imperfecta - genetic; osteoblasts are impaired and get very fragile skeleton Acromegaly - excess growth hormone and get skeletal deformities paget's disease - gradual deformation of the skeletal system |
