Bone fracture classification and repair / Calcium homeostasis / Ageing on Skeletal System Flashcards
what are the 4 steps of bone repair?
Hematoma Formation, Callus Formation, Callus ossification, Bone Remodeling
how does breaking a bone result in hematoma formation?
fracture —> blood vessels in the bone/periosteum damaged —> hematoma —> clot forms; disruption of blood vessels in central canal causes inadequate blood delivery to osteocytes, and bone tissue adjacent to the fracture site dies. tissues around the bone often become inflamed and swollen following the injury
why is remodeling of the ossified callus necessary?
Remodeling of the ossified callus is necessary because since woven bone is not as structurally strong as the original lamellar bone, then filling the gap between bone fragments with an internal callus of woven bone is not the end of the repair process. Repair cannot be complete until the woven bone of the internal callus and the dead bone adjacent to the fracture site are replaced my compact bone. As the internal callus is remodeled and becomes stronger, the external callus is reduced in size by osteoclast activity. The repaired zone usually remains slightly thicker than the adjacent bone, but the repair may be so complete that no evidence of the break remains.
how is calcium moved into and out of bone?
Calcium ions move into bone as osteoblasts build new bone, and they move out of bone as osteoclasts break down bone.
what happens in bone when blood calcium levels decrease and when the increase?
when decreased the osteoclast activity increases; when increased the osteoclast activity decreases.
name the hormone that is the major regulator of Ca2+ levels in the body. what stimulates the secretion of this hormone?
Parathyroid hormone (PTH) is the major regulator of Ca2+. ; Decreased blood Ca2+ stimulates PTH.
describe how PTH controls the number of osteoclasts
PTH stimulates an increase in osteoclasts when Ca2+ levels are too low.
what are the effects of PTH on the formation of calcitriol, Ca2+ uptake in the small intestine, and reabsorption of Ca2+ from the urine?
PTH promotes the activation of vitamin D in the kidneys, and vitamin D increases the absorption of Ca2+ from the small intestine. PTH also increases the reabsorption of Ca2+ from urine in the kidneys, which reduces the amount of Ca2+ lost in the urine.
what stimulates calcitonin secretion?
High blood Ca2+ levels
how does calcitonin affect osteoclast activity?
It decreases osteoclast activity by binding to receptors on the osteoclasts.
open fracture
end of fractured bone protrudes through open wound in skin; increases risk of infection
displaced fracture
ends of fractured bone move so that they are no longer aligned; more painful than other fracture types and may cause internal damage from the bone end
spiral fracture
a helical fracture from twisting of the bone; common in snow skiers whose feet and ankles are locked into ski boots
comminuted fracture
fracture results in at least 3 bone fragments; occurs in patients with weakened bones or from a severe accident; often necessary to surgically place a pin in the bone
greenstick fracture
fracture with the break on one side and bend on the other side of bone; typical in young children due to increased collagen percentage in bone
