Term
| What are the 4 cell types present in bone? |
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Definition
1) Osteoprogenitor cells: Stem cells
2) Osteoblasts: Synthesise the organic bone matrix
3) Osteocytes: Mature osteoblasts. Inactive
4) Osteoclasts: Erode mineralised bone and remodel. Their activity is regulated by osteocytes. |
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Term
| Which hormones stimulate the osteoclasts (via osteoblasts)? |
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Definition
1) Parathyroid hormone: stimulates
2) Calcitonin: inhibits. |
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Term
| Which 2 processes are involved in the production of bone? |
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Definition
1) Ossification: bone formation
2) Mineralisation: addition of a hydroxyapatite. |
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Term
| What are the 2 methods of ossification? |
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Definition
1) Intramembraneous: The formation of bone from connective tissue
2) Endochondral: The formation of bone from cartilage. |
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Term
| Describe the process of intramembraneous ossification. |
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Definition
1) Mesenchymal cells differentiate to osteoblasts
2) Ossification centre forms in membrane
3) Osteoblasts secrete osteoid
4) Forms mineralised bone matrix in spicules
5) Osteoid laid down between blood vessels fuse spicules and form the trabeculae of woven bone
4) Mesenchyme forms periosteum
5) Woven bone is remodelled to haversian bone. |
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Term
| Describe the process of endochondral ossification. |
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Definition
1) Hyaline cartilagte generated from mesenchyme
2) Cartilage deposited in the shape of future bone
3) Chondroblasts form perichondrium and then periosteum
4) Formation of bone collar
5) Cavitation of template
6) Chondrocytes proliferate
7) Calcium deposited in the cartilage matrix in the primary ossifcation centre
8) Bone deposited in diaphysis
9) Capillaries penerate periosteum and grow into diaphysis
10) Osteoprogenitor cells form osteoblasts in the primary ossification centre
11) Osteoblasts secrete osteoid bone matrix to form trabecular bone
12) Osteoid is mineralised
13) Collar and trabecular bone merge
14) Hyaline cartilage only remains in epiphyseal plate
15) Secondary ossification centre ossifies epiphyses. |
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Term
| What does the secondary ossification centre form from? |
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Definition
| Blood vessels and osteoprogenitor cells. |
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Term
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Definition
1) New cartilage added to the ends of diaphysis due to chondrocyte division in the epiphyseal plate
2) Osteoblasts produce osteoid on new cartilage
3) Cartilage converted to bone by endochondral ossification. |
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Term
| How is long bone growth regulated? |
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Definition
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Term
| What kind of disorder is osteogenesis imperfecta? |
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Definition
| An autosomal dominant genetic disorder. |
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Term
| What causes the symptoms of osteogenesis imperfecta? |
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Definition
| An abnormality of connective tissue- collagen improperly formed (not type 1). |
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Term
| What are the observations you would make about a patient with osteogenesis imperfecta? |
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Definition
1) Sclera has a blue, purple or gray tint
2) Hearing loss may be present
3) Triangular face. |
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Term
| Describe the stages of fracture healing. |
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Definition
1) Haematoma and inflammation, granulation tissue forms
2) Cartilage and osteoid laid down by osteoblasts to make a 'provisional callus'
3) Bone is remodelled by the action of osteoblasts and osteoclasts. |
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Term
| What is the difference between acromegaly and gigantism and what underlies these conditions? |
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Definition
| Gigantism and acromegaly involve the excessive growth of bones and other tissues due to abnormal levels of growth hormone. Gigantism occurs in children before the epiphyseal closure. Acromegaly occurs in adults after the closure. |
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Term
| What causes osteoporosis? |
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Definition
| A decrease in bone calcium (menopause: reduced estrogen). |
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Term
| What are the results of osteoporosis? |
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Definition
| Fewer and narrower trabeculae. |
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Term
| What is fibodysplasia ossificans progressiva? |
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Definition
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Term
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Definition
| A failure of mineralisation which can be caused by a high intake or low excretion of calcium/ phosphate ions. It results in the softening of bone leading to an increased susceptibility to fractures. |
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Term
| What is osteomalacia called in children? |
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Definition
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