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A&P wk8 Part2 AGAIN

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winniesmith's version from 2017-01-29 21:18

Section 1

Question Answer
3 types of bone growth Intramembraneous ossification, Endochondral ossification, Appositional bone growth.
Intramembranous ossification -Forms flat bones: skull, mandible, clavicle. -Stem cells differentiate to osteoblasts. -Produce spongy bone, then compact bone.
Intramembramous ossification process1.Mesenchymal cells aggregate, differentiate into osteoblasts, and begin ossification process. 2.Spicules interconnect, and trap blood vessels within the bone. 3Typical spongy bone formed. Over time, some may be remodelled into compact bone or medullary cavity.
what is ossification Ossification=conversion of tissues to bone.
Endochondral ossificationMost bones formed this way. Cartilage model replaced by bone: Replacement begins in middle (diaphysis): Replacement follows in ends (epiphyses)
Endochondral ossification processChondrocytes at the centre of the growing cartilage model enlarge and then die as the matrix calicifies. Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of bone.Blood vessels penetrate the cartilage. New osteoblasts form a primary ossification centre. The bone of the shaft thickens, and the cartilage near each epiphysis is replaced by shafts of bone.Blood vessels invade the epiphyses and osteo-blasts form secondary centres of ossification.
Appositional bone growthGrowth in bone width. Bone is deposited by osteoblasts (outside) and bone resorbed by osteoclasts (on inside ring).
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Section 2

Question Answer
Blood supply-
Nutrient artery and vein Enter the diaphysis through the nutrient foramen
Metaphyseal Vessels Supply the epiphyseal cartilage
Periosteal Vessels Supply superficial osteons
Requirements for normal bone growth-Minerals: Calcium, phosphate. -Vitamins: Vitamin D3 Vitamin C Vitamin A. -Hormones: Growth Hormone Sex hormones, thyroid hormone, others -Loading
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Section 3

Question Answer
What is remodellingContinuous breakdown and reforming of bone tissue. Shapes reflect applied loads.
Role of remodelling- mineral turnoverImportant for calcium homeostasis. 99% of calcium stored in bone. Hormones control storage/release: PTH releases bone calcium. Calcitonin stores bone calcium
age of Peak bone massusually in 30's
age of Bone lossfrom 40s, most rapid loss in women after menopause.
Remodelling of cortical boneOsteoclasts in osteon, form cutting cone. Osteoblasts form closing cone of osteoid (unmineralised bone)
bone loss particularly affects Trabecular (spongy) bone in epiphyses,vertebrae and jaws
How can you measure this?DXA Dual X-ray absorptiometry
What is osteoporosisis a systemic skeletal disease characterised by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture
Risk of osteoporosis1 in 2 for women and 1 in 5 for men
what is a fracture A crack or break in a bone
Steps in fracture repair (outline)Fracture haematoma. Mitoses in periosteum, endosteum: Internal callus, External callus. Bone remodeling.
Steps in fracture repair1. Bleeding and formation of clot (fracture haematoma). 2. Formation of external callus(cartilage) and internal callus(spongy bone). 3. External callus replaces by bone.Internal callus unites broken ends.4.Initial swelling and eventually remodelled.
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