diseases of the bone Flashcards
what are the purposes of bone?
to protect the organs, to support the body, to aid movement, to store calcium and minerals and to produce blood cells from the bone marrow
what are the components of bone?
there is cortical bone, trabecular bone, cells, extracellular components
what is the cortical layer?
it is the hard outer layer of bone
what is the trabecular layer?
it is the spongy inner layer
what types of cells are found in bone?
bone forming cells, bone resorbing cells and bone coordinating cells
what is the extracellular component of bone?
there is organic matrix and inorganic part
what is the organic matrix?
it makes up 30% of the extracellular layer and is made of mainly collagen for osteoid and ground substance
what is the inorganic part of extracellular material?
it represents 70% of the extracellular part and is made of hydroxyapatite which is calcium and phosphate and minerals such as magnesium, sodium and potassium
what is the anatomy of the bone?
the outermost layer is the periosteum membrane covering the bone, and then inner is the endosteum. Within the cortical layer is the endosteum and this contains the yellow marrow.. Inside the yellow marrow is vessels and nerves. Within the spongy layer is the red marrow and this contains the trabeculae
what is an osteon?
it is a unit of the compact bone. It contains lamellae, canaliculi, haversian canals and lacunae containing osteocytes
what connects haversian canals in the outer hard bone?
volkmanns canals
what is the main role of osteoblast?
they create and repair new bone
what do osteoblasts do in order to complete their function?
they mineralise organic matrix, they communicate with other bone cells, they become osteocytes, they make hormones and they also make osteoid
what are the characteristics of collagen?
it makes up most of the oteoid/ECM and is for tensile strength. It is produced by osteoblasts
what is hydroxyapatite?
it is calcium phosphate hydroxide salt and is involved in mineralisation
what is the function of bone remodelling?
it is vascular, metabolically active and is for cellular processes
what is the function of osteoclasts?
they break down old bone
what are the components of osteoclasts?
there is RANKL and PTL and IL-6
what is RANKL?
it is a osteoprotegrin that is a decoy receptor which binds and thereby opposes the RANK ligand which is another cytokine that activates osteoclasts and causes bone resorption
what is PTL?
it is a calcitonin that is produced in humans by the parafollicular cells or C cells of the thyroid gland - it is involved in helping to regulate the calcium and phosphate in the blood that opposes the action of the PTH
what is IL-6?
it is an interleukin that is a proinflammatory cytokine and an antiinflammatory myokine encoded by the IL6 gene. In addition osteoblasts secrete IL6 to stimulate osteoclast formation
what is the remodelling process in normal bone in adults?
normal bone is in constant state of turnover caused by resorption by osteoclasts and formation by osteoblasts - the adult skeleton is replaced every ten years
what is the process of making osteocytes?
it is an osteoprogenitor cell making an osteoblast and then making an osteocyte
what is the cross sectional structure of bone?
the outer layer is the osteoblasts and osteoclasts within them. Within the bone is the lamella with osteocytes between each one, and a central canal with a nerve, lymphatic vessel, artery and vein within it