BIOS 1300 Exam 3 with complete solution
osteoprogenitor cells
give rise to bone cells, found in perostium/endostium
osteoblasts
synthesizes organic matter of bone which hardens for mineral deposition
osteocytes
homeostatic maintenance for bone density and blood concentration of calcium/phos...
BIOS 1300 Exam 3 with complete solution
osteoprogenitor cells
give rise to bone cells, found in perostium/endostium
osteoblasts
synthesizes organic matter of bone which hardens for mineral deposition
osteocytes
homeostatic maintenance for bone density and blood concentration of
calcium/phosphate ions
sense stress of a bone
osteoclasts
bone dissolving cells on bone surface responsible for bone resorption
where are osteocytes found?
trapped in matrix reside in lacunae connected by canalicunae
what is considered apart of the organic matrix?
osteoblasts, collagen, GAG's and glycoproteins
What is considered inorganic material of the matrix?
hydroxyapatite, calcium, phosphate, salt
what does inorganic material provide?
strength
what does organic material provide?
flexibility
without enough organic material it causes?
brittle bones, osteogenesis imperfecta
without inorganic material it causes?
rickets/osteoporosis
basic nutrients required for bone matrix
vitamin D, Vitamin c, calcium, phosphate, protein
proteolytic enzymes role in bone resorption
chemically digest collagen fibers / proteoglycans
HCl role in bone resorption
dissolves mineral parts to let free Ca++ and phosphate into blood
Bone marrow
soft tissue in marrow cavity in a long bone and trabeculae of spongy bone
Red marrow
produces blood cells primarily in skull, vertebrae, ribs, sternum, and pelvis
Yellow marrow
fat
autologous bone marrow transplant
patients own stem cells are collected and transplanted back into the patient
allogenic bone marrow
a donor match is found or umbilical cord is used to be transplanted into the patient
Intramembranous ossification
begins in CT source of perostial bone collar, future dermis produces flat bone of the
skull
endochondrial ossification
,hyaline cartilage is replaced with bone tissue
when bones grow in length
interstitial growth
bone growth in width
oppositional growth
5 microzones in epiphyseal plate
reserve cartilage, cell proliferation, hypertrophy, calcification, deposition
wolffs law
shape of bone is determined by the stress placed upon it and adapts to withstand the
stresses
which hormone is faster estrogen / testosterone?
estrogen
what percent of skeletal tissue is replaced per year
10%
which hormone is important to many children in calcium regulation?
calcitonin
is bone production turned off after bone is made?
no, metabolically active organ
deposition
also known as mineralization = a crystallization of mainly hydroxyapatite by releasing
Ca/P into the blood stream and deposited into the bone tissue
When does bone deposition begin?
fetal ossification
etopic ossification
when bone forms in brain, eyes, muscle, tissue = abnormal
mineral resorption
process of dissolving bone, job done by osteoclasts, releases minerals into blood and
makes them available for other uses
which bone cell has surface receptors to respond to falling levels of calcium in
the tissue fluid?
osteoclasts
what does the body need to maintain for bone?
calcium/phosphate levels
normal pH of calcium
9.2-10.4
is it serious if calcium levels change slightly?
yes, causes hyper/hypocalcemia
Hypercalcemia
excessive amount of Ca+ in body, RARE, increases charge difference in sodium levels
and makes sodium less responsive causing channels to inhibit opening.
Hypocalcemia
not enough Ca+ in the body, serious effects causes excessive excitability of the nervous
system
what effects does Hypercalcemia have on the body?
emotional disturbances, muscle weakness, slow reflexes, cardiac arrest
what effects does hypocalcemia have on the body?
, tetany, spasms, treaussau's sign
what is calcium responsible for in body?
pacemaker, communication among neurons, muscle contraction, blood clotting,
exocytosis
what 3 hormones make up calcium homeostasis?
calcitriol, PTH, calcitonin
calcitriol process
form of Vitamin D3, process starts at ultraviolet rays from sun into epidermis, converting
cholesterol to pre-vitamin D3 goes in blood stream through liver, added hydroxy group
in liver, becomes calcidiol goes though kidneys another hydroxy group added becomes
calcitriol
what is the most active form of vitamin D3
calcitriol
why is calcitriol considered a vitamin?`
because it is added to the diet (mainly in fortified milk)
function of cacitriol
raise blood calcium concentration in 3 ways
1. stimulate absorption of calcium from small intestine to build bone
2. stimulate osteoclasts to liberate Ca++ into blood
3. reabsorb calcium in kidney to decrease amount of Ca++ lost in the urine
Calcitonin
secreted by C-cells of the thyroid gland, secreted when Ca+ levels are too high
what is a reason why Ca+ levels would be high and why calcitonin would be
released?
excessive exercise/stress
which hormone for maintenance of calcium levels is most important in children?
calcitonin
what is the function of calcitonin
lower Ca++ concentration
1. osteoclast inhibition by 70%
2. stimulation of osteoblasts and deposits calcium into the skeleton
3. stimulates kidneys to high loss of calcium in urine
what are pathologies caused by reduced amount of Vitamin D (calcitriol)
rickets, osteomalacia, decreased immunity
PTH
secreted by parathyroid hormone in response to low blood calcium levels
function of parathyroid gland
promotes final step in calcitriol synthesis
1. release ca++ into blood by increasing osteoclast population
2. increase reabsorption of Ca++ by kidney to avoid loss in urine
stress fracture
fracture caused by abnormal repeated stress to a bone.
athletics, falls, trauma, military combat
difficult to see on a bone scan
pathological fracture
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