main points lecture 6 part 2 Flashcards
what is ossification
process of forming new bone
under what four conditions does ossification occur
formation in late stage embryo
growth until adulthood
remodeling of bone
fracture repair
steps of intra-membranous ossification
mesenchymal cells develop into osteoblasts in a fibrous membrane
what bones are made by intra-membranous ossification
flat bones of the skull, mandible, and clavicle
what type of bone is made by intra-membranous ossification
spongy bone
steps of endochondral ossification
primary ossification center, bone collar
cartilage calcifies and develops cavities
spongy bone forms
secondary ossification centers form in the epiphyses
what bones are made by endochondral ossification
long bones
what type of cartilage is used in endochondral ossification
hyaline cartilage
cartilaginous remnants found on bones produced by endochondral ossification
hyaline cartilage in the epiphyseal growth plate and articular cartialges
what type of bone growth is longitudinal growth
endochondral ossification
what does longitudinal growth require
the presence of epiphyseal cartilage
five zones within epiphyseal growth plate
resting (quiescent) zone
proliferation (growth) zone
hypertrophic zone
calcification zone
ossification (osteogenic) zone
resting (quiescent) zone characteristic
relatively inactive
proliferation (growth) zone characteristic
rapidly dividing by pushing epiphysis away from diaphysis
hypertrophic zone characterstic
older chondrocyte enlarge
calcification zone characteristics
matrix calcifies, cartilage cells die, blood vessels invade
ossification zone characteristics
new bone forms
what happens to the epiphyseal growth plate toward the end of puberty
thins and is replaced by bone, bones lengthening decreases, bones of epiphysis and diaphysis fuse
differences in timing for males and females
males 21
females 18
how can bone growth plate be affected if epiphyseal growth plate is damaged
stunts bone growth, might cause uneven limb size
what type of bone growth is appositional bone growth
sideways, thickening of bones
does appositional bone growth end with puberty?
no
where is most of new bone matrix laid down during appositional bone growth
periosteum
where is most of old bone matrix dissolved during appositional bone growth
endosteum
discuss rate of resorption vs. deposition in appositional bone growth
must be balanced but usually more building up than breaking down to allow for thickening
essential minerals for bone growth and remodeling
calcium, phosphorous, magnesium, fluoride, manganese
what vitamins are necessary for bone growth and remodeling
vitamin A,C, D, K, B12
vitamin A importance
activity of osteoblasts
vitamin C importance
synthesis of collagen
Vitamin D importance
promotes absorption of calcium from foods in the GI tract
Vitamin K and B12 importance
synthesis of bone proteins
what occurs with low vit D and/or calcium deficiency
children - rickets
adults - osteomalacia
what hormones are necessary for bone growth in children
human growth hormone, and growth factors
necessary to stimulate osteoblasts, promote cell division at the epiphyseal plate. enhance protein synthesis
what hormones are necessary for bone growth and remodeling in adolescents and adults
thyroid hormones - ensures bone proportions
sex hormones - growth spurt in adolescence
negative feedback for calcium
parathyroid hormone removes calcium from bone when blood calcium is too low
What is PTH, where is it made, what are the results
parathyroid hormone
produced in parathyroid glands
removes calcium from bone regardless of bone integrity
what is calcitonin, where is it made, what are the results
produced by parafollicular cells of thyroid gland
high doses lower blood calcium levels temporarily
what hormone is primarily responsible for day to day regulation of bone remodeling
PTH
parathyroid hormone
what causes the release of PTH
low blood calcium levels
how and on what does PTH work
stimulates osteoclastic activity and raises blood serum calcium levels
stimulates reabsorption of calcium ions in kidney
result of PTH release
increase blood calcium levels
what hormone contributes to daily remodeling to a lesser extent
calcitonin, hGH, and sex hormones
what hormone contributes to daily remodeling to a lesser extent. how they work, what is result
calcitonin, hGH, and sex hormones
stimulate osteoblastic activity and lower serum calcium level
how is bone remodeling affected by stress and lack of stress
bones thicken where they are stressed the most due to mechanical and gravitational forces
what aspect of bone remodeling do hormones control
if necessary and when necessary
what aspect of bone remodeling do mechanical/ gravitational forces control
where remodeling is necessary
how are fractures acquired in youth and elderly
youth - trauma
elderly - weakness due to thinning
fracture classifications - position
non-diplaced - bones aligned
displaced - bones out of alignment
fracture classification - completeness of break
complete - all the way
incomplete - not all the way
fracture classification - skin penetration
compound (open) - penetrated
simple (closed) - non penetrated
four other ways fracture are classified
location of fracture, external appearance, nature of break, eponym (name of someone)
how are fractures treated
reduction - realignment of broken bones
immobilization - cast or traction
steps of fracture repair
hematoma formation
fibrocartilaginous callus forms - about a week
bony callus forms - about two months
bone remodeling - several months
two principle effects of aging on bone
loss of bone - loss of calcium
brittleness - decrease of collagen fibers and protein synthesis
concentrations of sex hormones change as we reach later years
drop in hormone levels
women drop in estrogen is more significant than male drop in testosterone
what is osteoporosis
bone resorption outpaces bone deposition
what causes osteoporosis in youth
depletion of calcium from the body
what causes osteoporosis in aging and elderly
sex hormone changes
what bones are highly susceptible to osteoporotic fractures and why
spongy bone of spinal column and neck of femur
additional risk factors for osteopororisis
petite body, insufficient exercise, poor diet in calcium and protein
smoking
hormone related conditions - hyperthyroidism, low blood TSH, diabetes mellitus, low hGH and IGH production
immobility
males with prostate cancer taking androgen suppressing medication
