Flashcards in 1- Bone Deck (50)
What is endochondral ossification?
formation of LONG bones (any bone that grows longitudinally) from cartilage model, most common type of ossification
What is intramembraneous ossification?
this form does NOT use a cartilage model when forming the FLAT bones (clavicle/skull).
During the 6th week of bone development, the mesenchymal cells in the middle of the limb differentiate into what type of cells?
What is the fxn of chondoblasts?>
form the cartilage template of bone.
After the mesenchymal cells die, blood vessels migrate into the bone matrix bringing with them what type of cells?
What is the fxn of osteoblasts?
which form the bone by secreting osteoid into the bone matrix
At what location does the matrix get calcified?
primary ossification center
What is the diaphysis?
the shaft of a long bone where the primary center of ossification is located
What is the medullary canal?
central core located w/in diaphysis that is hollowed out by resorption creating a cavity for blood vessels which bring the osteoblasts
What is the metaphysis?
the knobs/flared region at the ends of long bones
What is the epiphysis?
located across the physis just below the articular cartilage lining the joint
What is the periosteum?
appositional growth (bone widening) occurs under the periosteum (sleeve of connective tissue surrounding the shaft). The periosteum remains into adulthood and is a the source of cells for fracture repair and new growth. Repair of bones does not stop as scar formation like other tissue; rather it completely re-ossifies leaving little or no indication of damage
What is the reserve zone of the physis?
closest to epiphysis, contains cells that produce a cartilaginous matrix of type II collagen which is used for bone ossification. Smallest blood supply
What is the zone of proliferation of the physis?
cells stack into columns where they undergo synthesis and cell division, and excrete extracellular matrix. Largest blood supply.
What is the zone of hypertrophy of the physis?
zone closest to calcified bone; the chondrocytes swell and become larger and participate in mineralization of the cartilage. Broken down into 3 zones. Poor blood supply but highly metabolically active so the cells use stored glycogen.
What are the 3 zones of the zone of hypertrophy?
(1) Zone of Maturation: chondrocytes store Ca
(2) Zone of Degradation: chondrocytes die via apoptosis and release Ca
(3) Zone of Calcification: Ca released is used for mineralization.
What is the zone of ossification of the physis?
Osteoclasts and osteoblasts from the diaphyseal side break down the calcified cartilage and replace with mineralized bone tissue
What is woven bone?
primitive less-organized bone that is formed when calcified cartilage is replaced with bone by osteoblasts. Haphazard orientation.
What is lamellar bone?
occurs when woven bone is remodeled to mature bone that is well organized and is aligned for load bearing.
Which artery supplies the growth plate?
the epiphyseal artery, which loses it prominence when the growth plate closes.
What is an osteoblast?
bone forming cells. These cells make the nonmineral (organic) component of bone, primarily the osteoid which is a protein matrix of collagen type I. They also regulate the mineralization of osteoid
Osteoblasts make what substance which is involved in bone formation and is an important clinical marker for people forming boning (fractures)?
Who do osteoblasts contain a large golgi apparatus?
they are metabolically active
What is an osteocyte?
osteoblasts that get trapped in established bone. They communicate with other osteocytes via processes that traverse canaliculi. This allows them to regulate the metabolic environment and respond to signals at the surface of bone.
What are osteoclasts?
multinucleated cells (from fusion of monocyte precursors) that break down bone. Derived from stem cells. Have a ruffled border to increase surface area in contact with bone (active osteoclast). Stimulated by signals such as PTH.
What are Howship's lacunae?
pits that osteoclasts sit in to resorb bone
What is the process of osteoclastic resorption of the bone?
osteoblasts expose part of the bone, the osteoclasts attach to this exposed bone via integrins and release proteolytic enzymes and hydrogen ions that break down the bone and release Ca via solubilizing Ca hydroxyapatite crystals (stored form of Ca in bone).
What is the histology and microanatomy of cortical bone?
dense bark-like, with it collagen aligned in the direction of applied forces. The cortex of bone is found at the periphery and is responsible for skeletal homeostasis
What is an osteon?
basic unit of cortical bone that allow it to remodel, in the center is an artery, and surrounding it is rings of lamellar bone.