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WEEK 24:
Bone 1:
| Question | Answer |
|---|---|
| S+F - 4-8 | |
| ECM | |
| hyaline cartilage | homogenous - nests so cannot differentiate which |
| fibrocartilage | chondrocytes arranged in rows in a matrix containing type I collagen bundles in rows (and type II) where perichodrium is absent - found in intervertebral discs, pubic symphysis, joint capsules, ligaments and tendons |
| functions of bone | mechanical support + protection, reservoir for calcium + phosphate, and supports haematopoiesis - bone marrow |
| bone organisation | dense outer shell (compact bone) and inner spongy/ cancellous bone (arranged in interconnecting trabeculae with spaces for bone marrow) |
| periosteum | fibrous connective tissue layer limiting bone (not present at joint ends of long bones) |
| endosteum | lines interior of bones |
| bone matrix made of | organic (osteoid) and inorganic parts |
| organic part of bone matrix | produced by osteoblasts, collagen type I with tensile + compressive strength and non collagenous proteins which mediate mineral deposition |
| inorganic part of bone matrix | calcium phosphate (hydroxyapatite), deposited in organic matrix making 66% of dry weight and hardness |
| bone cells | are from mesenchymal stem cells and differentiate into osteoprogenitor cells which then differentiate into osteoblasts which differentiate into osteocytes |
| osteoblasts | lay down organic bone matrix and mediates mineralisation of osteoid |
| when do osteoblasts become osteocytes | when surrounded by mineralised bone |
| osteocyte | maintains matrix |
| osteoclasts | bone resorbing/ eating cells |
| immature bone | WOVEN BONE - haphazard fibre arrangement, mechanically weak - fracture repair |
| mature bone | lamellar bone- regular parallel collagen, strong: all adult bone, arranged as osteons (aligned with direction of force) |
| how is the availability of calcium + phosphate controlled | matrix vesicles contain enzymes + proteins so that mineral is precipitated |
| brittle bone disease (OI- osteogenesis imperfecta) | |
| compact bone made of | made up of osteons |
| osteons of compact bone | functional units that act as weight bearing pillars, made up of concentric rings of lamellar bone around a central nutrient canal |
| central canal of compact bone contains | blood vessels, lymph vessels and nerves |
| perforating canals | run at right angles to central canals |
| mature/ trabecular bone - s24** | contain lamellae with osteocytes in lacunae connected to one another via canaliculi, similar to osteon arrangement in compact bone. Trabeculae do not have central canals or perforating canals containing blood vessels etc... |
| compare trabecular bone and osteoporosis | |
| osteoporosis | thinning of both cortical and trabecular bone but thinned trabeculae are prone to fracture - eg hip fracture dowager hump |
| bone turnover | continuous process where old bone tissue is broken down by osteoclasts and replaced with new bone tissue by osteoblasts |
| importance of bone turnover | allows bone to constantly remodel and repair itself maintaining its strength and structure (remodelling) |
| cortical bone bone turnover | dense outer layer- has a slower turnover rate compared to trabecular bone (spongy inner bone) |
| factors affecting turnover (2) | hormones (eg oestogren, parathyroid hormone - PTH), and vitamin D |
| bone remodelling phases | resting, resorption, reversal, and formation |
| osteoclasts | bone resorbing cell, phagocytic cell (from monocyte macrophage cell line), multinuclear and mobile (attaches to bone surface and resorbs bone leaving a pit behind - howships lacuna), and work with osteoblast to regulate bone turnover + remodelling |
| remodelling phases s34 | |
| how can bone turnover increase (4) | function (onset of walking), new demands (running, tennis etc), repair of fractures, and disease (eg pagets disease) |
| relationship between osteoblasts + osteoclasts s37 | |
| other pathways | direct cell -cell contact and cytokine signaling |
| direct cell-cell contact | osteoblasts + osteoclasts directly interact through cell adhesion molecules eg E-cadherin, which facilitates signaling between two cell types |
| cytokine signaling | |
| factors that can disrupt balance | hormonal imbalances, mechanical stress, ageing |
| osteoporosis - clinical |
Created by:
kablooey
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