1516608
Description
Flashcards by Hannah Tribe, updated more than 1 year ago
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Created by Hannah Tribe
over 9 years ago
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| Question | Answer |
| What are the 2 components of the macrostructure of bone? | 1. Cortical bone 2. Trabecular bone |
| What are the differences between these 2 types of bone? (4) | 1. Trabecular bone has a lower density 2. Cortical bone has a lower surface area 3. Cortical bone is made up of Haversian systems, whereas trabecular bone is made of struts and plates 4. Trabecular bone has a higher remodelling rate |
| What are the 3 main components of bone? | 1. Proteins forming the organic osteoid matrix 2. Minerals (calcium and phosphate) 3. Cells |
| What is the main component of the protein matrix? | Type 1 collagen |
| What is the function of this organic matrix? | It gives flexibility and tensile strength |
| In which disease is there a disorder in the type 1 collagen and therefore results in brittle bones? | Osteogenesis imperfecta |
| What is the name of the mineral component of bone? What is it made up of? | Hydroxyapatite, made up of hydrated calcium and phosphate |
| What is the function of the mineral? | It provides rigidity and high compressional strength, although it is brittle |
| What diseases can result from abnormal mineralisation? | Osteomalacia and rickets |
| What is the difference between them? | Osteomalacia occurs in adults once the growth plates have closed, yet rickets occurs in children before the growth plates have closed and thus results in deformities (bowlegs) |
| In normal people, what proportion of bone is mineralised? How is this different in osteomalacia? | Normal - 80% mineralised, 20% unmineralised Osteomalacia - 50/50 |
| What are the functions of osteoblasts? (2) | 1. synthesis matrix proteins 2. Form new bone material |
| Where do osteoblasts originate from? | Mesenchymal stem cells |
| What is the function of osteoclasts? | Resorb bone |
| How do they do this? | 1. Form a sealing zone around an area of bone, then produce and release acid into the zone to resorb the mineral content 2. Produce and secrete proteolytic enzymes to break down the organic matrix |
| Where do osteoclasts originate from? | Haematopoietic stem cells |
| What is a characteristic of osteocytes? | Lots of dendritic processes to allow interconnections |
| What are 3 functions of osteocytes? | 1. Sense mechanical stress 2. Produce sclerostin 3. Regulate phosphorus homeostasis |
| What is sclerostin? | A hormone made by the osteocytes, which affects bone turnover |
| Why is there a more sudden decrease in bone mass in post-menopausal women? | There is now a lack of oestrogen |
| What diseases can result from an imbalance between the formation and resorption of bone, and what is the difference between them? | Osteoporosis, which is a generalised imbalance favouring resorption. Paget's disease, which is a localised disruption of bone turnover, resulting in increased formation but brittle bones |
| Which hormones play a role in increasing bone density? (3) | 1. Oestrogen (androgens) 2. Growth hormone (causing production of IGF-1) 3. Calcitonin |
| Which hormones work to decrease bone density? (3) | 1. Thyroxine 2. glucocorticoids 3. PTH |
| What are the 3 stages of fracture healing? | 1. Macrophages remove debris, granulation tissue and fibrous, vascularised tissue is deposited. 2. Osteoblasts lay down a soft callus (woven bone) which gets mineralised to form a hard callus 3. Lamellar bone is formed and remodelling from the hard callus |
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