Bones

Hannah Tribe
Flashcards by Hannah Tribe, updated more than 1 year ago
Hannah Tribe
Created by Hannah Tribe almost 6 years ago
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Degree MSS1 Flashcards on Bones, created by Hannah Tribe on 23/10/2014.

Resource summary

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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