Bone histology Flashcards
what are the components of the bone matrix?
organic (35%) = collagen and proteoglycans
inorganic (65%) = hydroxyapatite
mineral components = weight bearing strength
collagen = flexible strength
how do the components of the bone matrix contribute to bone flexibility and bones’ ability to bear weight?
mineral is reduced,collagen is increased = bone is flexible
collagen is reduced, mineral is increased = bone is very brittle
what are the characteristics and functions of osteoblasts?
bone building cells; produce collagen and proteoglycans, which are packaged into vesicles by the golgi apparatus and secreted by exocytosis; also secrete matrix vesicles
what are the characteristics and functions of osteocytes?
osteoblasts become osteocytes; osteocyte cell bodies can be found in the lacunae; and their cell extensions are housed in narrow, long spaces = canaliculi
what are the characteristics and functions of osteoclasts?
bone destroying cells; derived from stem cells red bone marrow
what are the names of the spaces that are occupied by osteocyte cell bodies and cell extensions?
osteocyte cell bodies = lacunae
cell extensions = canaliculi
what cells give rise to osteochondral progenitor cells?
mesenchymal cells
what kind of cells are derived from osteochondral progenitor cells?
osteoblasts
what types of cells give rise to osteoclasts?
the stem cells from red bone marrow
how is the organization of collagen fibers different in woven and lamellar bone?
in woven bone, the cartilage fibers are randomly oriented in many directions; in lamellar bone, cartilage fibers lie parallel to one another, but at an angle they lie in a adjacent lamellae
what process produces woven bone?
ossification
what are trabeculae and what is their function?
interconnecting rods or plates of bone; provides strength and transfer external load away from the joint and toward the cortical bone
how do osteocytes within trabecule obtain nutrients?
they obtain their nutrients through the canaliculi
what is an osteon?
functional unit of a long bone; also known as haversian system
what are the names of the 3 types of lamellae found in compact bone?
concentric lamellae, circumferential lamellae, and interstitial lamellae
matrix vesicles
contain high concentration of calcium and phosphate; when these reach a certain level hydroxyapatite crystals form
ossification
formation of new bone by osteoblasts; occurs by appositional growth on the surface of existing material, either bone or cartilage; can occur as a fetus, when growing, or in bone repair
hydroxyapatite crystals
acts as template that stimulates hydroxyapatite formation and mineralization of the matrix
bone reabsorption
breakdown of bone; important for mobilizing crucial calcium and phosphate ions for use in many metabolic processes; as bone breaks down the calcium goes back to the bloodstream
podosomes
develop and form a sealed compartment under the osteoclast
ruffled border
specialized reabsorption-specific area of the membrane; acidic vesicles fuse with membrane of ruffled border, while ATP-powered H+ pumps and protein-digesting enzymes are inserted into the membrane of ruffled border
woven bone
formed first, weak, osteoclasts will break down and osteoblasts build lamellar bone
lamellar bone
mature bone - arranged in concentric sheets called lamellae
what are the two types of bone formed during ossification
woven and lamellar bone
