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23 Cards in this Set
- Front
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Describe the composition of carilage in terms of its cells and extracellular components.
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Cartilage is non vascular connective tissue that is composed of chrondrocytes ( maintain extracellular matrix) which are found in clusters inside a lacuna called a territorial matrix.
The extracellular matrix is composed of collagen fibres and ground substance ( proteoglycans and glycosaminoglycans) which give cartilage its resilience, non-compressibility and elasticity. It is therefore able to support soft tissues (keep airways open) and due to its smooth surface, provide a sliding area for joints |
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Clasify the 3 major types of cartilage, describing the structural differences between them.
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Hyaline: most common carilage
- many chondrocytes - type 2 collagen fibres - has a perichondrium ( vascular dense CT contains chondroblasts and chondrogenic cells) - calcifies/ossifies with age - found in articular cartilage on bones Elastic - more chondrocytes than hyaline - some collagen - contains elastic fibres - has a perichondrium - found in epiglotis - doesn't calcify or ossify with age Fibrocartilage - thick type 1 collagen ( no type 2) - few chondrocytes - no perichondrium - doesn't calcify or ossify with age - intervertebral disc |
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relate the different anatomical distribution of hyaline cartilage to its different functions.
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Hyaline: the most common caritlage found in the adult in the larynx, conductance portion of respiratory system, parts of ear and nose, ribs and in articular cartilage of the joints.
In the embryo it is the tempory skeleton before being replaced by bone. TRACHEA: Position: C shaped hyaline cartilage found inbetween submucosa and smooth musle (muscularis externa) Function: Keeps airways open - interterritorial matrix does not stain as well as territrorial matrix as contains more water ( although contains more collagen and less ground substance) ARTICULAR CARTILAGE: Position: Covers ends of two bones eg mallory's trichrome in full term foetus Function: smooth surface provides a sliding area for joints, friction free movement. Allows shock absorption( non compressibility) - no perichondrium as merges with other tissues - high water content within matrix resists compression -loss of water caused by prolonged pressure can be rectified by water in synovial fluid or blood vessels - if damaged can't repair itself - chondrocytes mature, hypertrophy and calcify - endochondral ossification INTERCOSTAL RIBS: costal cartilage between sternum and rib Position: end of ribs, Function: allow elasticity of thoracic cavity EARS & NOSE: - helps to retain show and allow bending |
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What is the perichondrium and where is it found?
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The perichondrium is a vascular dense CT the covers hyaline and elastic cartilage. It contains chondroblasts and chrondrogenic cells. Chondrogenic cells, found on the inner side of perichondrium develop into chondroblasts which secrete extracellular matrix.
chondrocytes in the cartilage maintain the extracellular matrix and recieve nutrients from the perichondrium. |
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Relate the different anatomical distribution of elastic and fibrocartilage to their different functions.
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ELASTIC CARTILAGE is found in:
- external ear, epiglottis( attached to pharynx near base of tongue) and the walls of the eustachain tube(connects pharynx to middle ear) - gives tissue shape and provides grater flexibility and elasticity than hyaline cartilage - yellow due to elastin FIBROCARTILAGE - found at sites of directional stress - usually intermediate between dense connective tissue and hyaline cartilage - it has considerable strengh and resistance to compression - no perichondrium as blends with other tissues - intervertebral discs (annulus fibrosus containing nucleus pulposus) - certain articular cartilages - symphysis pubis - between certain tendons or ligaments to bones. |
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Explain the regeneration capacity of carilage
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Adult cartilage is incapable of regeneration when damaged as adult chondrocytes can't divide. Tearing or damage is repaired by dispositon of scar tissue ( connective tissue) derived from perichondrium.
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Describe the characteristic features and functions of the different types of bone in the body
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Primary bone - immature bone ( yet to be mineralised) , woven structure.
Seconday bone - Mature bone, lamellae, mineralised. 2 types of secondary bone: Spongy (cancellous): - central core of bone - framework of bony trabecullae containing osteocytes and osteoblasts. - spaces filled with bone marrow( - red marrow - haemopoetic yellow marrow- stores adipocytes - vascular Compact bone: - outer layer - Series of haversian canals/osteones - haversian canals are Conentric lamellae with trapped osteocyctes centred around a haversial canal containing blood vessels - Interstitial lamellae fills spaces between haversian sytems - haversian canals supply nutrients to the osteocytes from nutrient supply in periosteum via volkmann's canals - osteocytes have processes which run into canaliculi in the bone so that nutrients from H canal diffuse into haversian and are absorbed by processes. - osteocytes in adjacent layers communicate via gap junctions. FUNCTIONS: support, protection, mineral storage( calcium hydroxapatite crystals) and haemopoiesis. |
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Describe the periosteum and endosteum.
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The periosteum is a vascular dense connective tissue sheath that surrounds bone. Its outer layer is mainly fibrous ( fibres, fibroblasts) but it's inner layer contains osteoprogenitor (stem) cells that can develop into osteoblasts. These osteoblasts lay down bone in sheets forming the outer circumferential lamellae of compact bone.
The endosteum covers the marrow cavity and is composed of osteoprogenitor cells, osteoblasts and occational osteocytes ( osteoblasts trapped in calcified bone matrix) |
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Describe the composition of bone in terms of its cells and extracellular components.
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Bone is a solid special connective tissue
Collagen is the main protein present 60-70% of bone comprises of mineral salts eg calcium hydroxyapatite crystals. Inorganic salts and collagen form interactions so that bone is rigid but also flexible. Cells: osteoblasts - found on surface of bone and secrete calcified bone matrix osteocytes - osteoblasts that are trapped within matrix osteoclasts - large multinucleated cells formed from monocytes that digest bone. |
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Explain how bone is a living tissue undergoing remodelling and repair.
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osteoblasts - secrete calcified bone matrix
osteoclasts - break down bone matrix to release calcium ions to blood on stimulation from parathyroid hormone/ inhibition from calcitonin osteocytes - mature osteoblasts that maintain bone matrix Requires blood, lymph and nerve supply. Marrow produces RBCs and WBCS - haemopoetic |
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Describe the cellular processes involved in bone repair following a fracture.
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Bone is the only solid tissue in the body that can heal without scar tissue.
- A bone fracture damages the blood vessels in the periosteum and in the haversian and volkmann's canals causing haemorrhage. - The site of injury therefore fills with blood ( haematoma) to form a clot between the broken ends of the bone which become necrotic - Macrophages and osteoclasts invade and remove the dead tissue and dead bone cells. - Proliferating cells of periosteum such as fibroblasts and chondrocytes invade area between broken bones forming a procallus that bridges the fracture site. - Hyaline cartilage is produced which forms the hard mass, the callus which temporarily binds the 2 bone ends together. -Endochondral ossification takes place as osteoblasts replace cartilage with cancellous bone which is transformed into compact bone. - Newly formed bone is much wider in diameter than the original bone so remodelling occurs to return bone to normal size shape and strength |
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Describe the process of intramembranous and endochondral ossification as related to bone growth.
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Endochondral ossification.
- Takes place in growth in length (epiphysis) and diameter ( diaphysis) in long bones using a hyaline cartilage template From embryo to adult 1. Embryo skeleton comprises entirely of hyaline cartilage 2. The mesenchymal cells in the outer rim of the long bone develop into osteoblasts and start laying down bone in the centre of the shaft. 3 . The chondroblasts hypertrophy in the centre of the shaft- diaphysis and the matrix becomes calcified - primary ossification centre - growth in diameter 4. Postnatal much of the shaft is calcified except the blocks of cartilage separating epiphysis from diaphysis. The cartilage makes up the epiphyseal growth plates. 5. Secondary ossification centres develop in epiphysis and by puberty all the heads and shaft have been calcified. 6. The epiphyseal growth plates remain, allowing continual growth in length as cartilage cells divide, mature and hypertrophy. 7. In adulthood growth plates are ossified and no more growth in length can occur, however articular cartilage remains - friction free movement. Intramembranous ossification - takes place in flat bones of the skull using mesenchymal connective tissue template - mesenchymal cells differentiate into osteoblasts which produce osteoid ( collagen and proeoglycans) - osteoid is mineralised into bone. - extensive trabecullae form to produce cancellous bone - peripheral regions become compact bone |
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What are the zones of ossification?
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1. Zone of resting cartilage
2. Zone of proliferation 3. Maturation zone 4. Zone of hypertriophy- chondrocytes enlarge 5. Zone of calcification - Osteogenitor cells from periosteum invade hypertrophy zone and cover the cartilage in a layer of osteoid ( collagen & proteoglycans). The osterod is mineralised into bone and replace cartilage cells. |
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Explain how the morphology and or mechanical properties of bone can change in disease ( including bone matrix and psychosocialy)
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Achondroplasia:
- dwarfism - disproportionate shortness - failure of proliferation and column formation in zone of proliferation, thin epiphysial growth plate - large amount of calcified cartilage present in bone, can't support bone matrix produced from osteoblasts - doesn't affect head as flat bone - intramembraneous ossification Socially: dwarf- less than 4 feet, sterotypes, can't have children Osteogenesis imperfecta - Defect in collagen synthesis by osteoblasts and fibroblasts - affects all CT - bone, tendon, teeth etc - Britte bone, predisposed to fracture - fracture - poor alignment and weak callus produced - blue sclera - can see vein - severe - bone breaks before birth - death Osteoporosis: After 30 yrs old bone density decreases and becomes more suscepitble to fractures Females are more susceptible to osteoporosis as menopause decreases levels of oestrogen. Oestrogen activates osteoblast activity and inhibits osteoclasts. Therefore after menopause bone resorption becomes greater than bone deposition, reducing bone density. medullary cannals in centre of bone become enlarged and gaps develop in lamellae making bone more fragile. Paget's disease: Rare disease in elderly where bones become enlarged and porous so more susceptible to fractures. Spine, skull and legs particularly at risk. Elevated levels of alkaline phosphatase which is released by osteoblasts and shows very high turnover of bone. Osteopetrosis: - Rare heriditary disease of the skeleton - all bones are affected - increase in density and thickness of long bones but unstructured and fragile - Increased trabeculae and reduced marrow and haversian cannals. - Reduced haemopoesis causing anaemia and extramedullary haemopoesis leading to splenomegaly, hepatomegaly, enlarged lymph nodes - mostly primary, woven bone |
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Describe the genetic basis and histological changes in osteogenesis imperfeca and its potental medicolegal importance.
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Osteogenesis imperfect is a genetic defect of the collagen synthesising cells, fibroblasts and osteoblasts.
The disease can be detected before birth, prenatal testing - legal implications of abortion. Giving birth may kill foetus |
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Explain the importance of Vitamin D in normal bone development.
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Vitamin D is needed for absorption of calcium from diet. Therfore low levels of vitamin D cause defficient ossification as the bone matrix is poorly mineralised- low in calcium ( calcium hydroxyapatite crystals)
High levels of vitamin D can be toxic however with increased bone resporption leading to hypercalcemia. |
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Describe the features of bones affected by rickets and osteomalacia and appreciate the difference between the 2 conditions.
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Both conditions are vit D deficencies causing soft bone which are unable to support weight.
Rickets- occurs in children, softening of bones which are prone to fracture and deformity. bones don't ossify properly - poor bone matrix mineralisation due to lack of calcium absorption. Osteomalacia - recently formed bones don't ossify and existing bone may decalcify. Treatment: vitamin D supplements eg cod liver oil, calcium, phosphates, sunlight exposure Without treatment - immobility |
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Describe the radiological and histological changes occuring in osteoporosis
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Bone density decreases with age as osteoblasts aren't activated as much and osteoclasts are. Bone resorption > bone deposition.
collagen framework degraded and demineralisation ( gaps develop in lamellae) as medullary canals enlarge. |
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List the most common risk factors of osteoporosis
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- age - over 30 bone density decreases
- postmenopausal women- oestrogen levels decrease - hormone which activated osteoblasts and inhibited osteoclasts - genetics - smoking - nutirion - activity/exercise - hormone linked diseases |
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Explain the importance of osteoporosis as a risk factor for fractures in the elderly
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Osteoporosis: reduces bone matrix and structure and all reduces mineralisation causing Brittle bones which are more likely to fracture under daily stresses.
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Outline the causes and morphological features of achondroplasia.
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- short limbs - dwarf - less than 4 ft
- enlarged skull - intramembraneous ossification can occur - small face - flat nose Autosomal dominant point mutation: single base substitution ( G->A) causing amino acids substitution Gly -> Arg on FGFR-3 protein ( fibroblast growth factor receptor) which affects production and maintaince of bone. - decreases endochondral ossification - thin epiphysial ground plates - inhibits proliferation of chondroblasts on growth plates. - decreases hypertrophy of chondrocytes - coluum formation - increases calcified cartilage cells in bones which can't support bone matrix produced by osteoblasts |
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Outline the effects of abnormal levels of growth hormone and sex hormones on bone development.
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Growth hormones:
children: Deficiency: - affects epiphysial cartilage - pituitary dwarfism Excess: - excessive growth of long bone - gigantism Adults: epiphysial plates haves fused together but growth occurs by sub-periosteal formation leading to acromegaly ( pituitary adenoma) - enlarged hands, facial features - occurs middle aged. Sex hormones - influence ossification of epiphysial plates. Deficency - prolonged bone growth in length as epiphysial plates not closed when they should be - tall stature Excess - sex hormone producing tumour - retarded growth as premature ossification of epiphysial growth plates. |
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What are the affects of abnormal levels of thyroid hormones and parathyroid hormone.
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Thyroid hormone deficiency
- Stunted physical and mental development - Cretinism Parathyroid hormone Excessive amounts - Stimulate osteoclast activity - Increases resorption of bone matrix - Increases blood levels of calcium and phosphate Increased deposition of calcium in kidneys and arterial walls |
