4.6 Endocrine Ca and PO4 Flashcards
is calcium or phosphate regulation more important?
calcium
calcium regulation is specifically critical to?
1) neuronal excitaility (stabolize nueromuscular membranes)
2) cardiac muscle contraction (regulate release of sarcopplasmic reticulum)
3) hemostasis (blood clotting)
4) mineralization of tissues
low Ca levels make neuromuscular membranes?
hyperexcitable; leaky to Na causing partial depolarization
how do you get hypocalcemic tetany?
low plasma Ca =
plasma membranes leaky to Na=
partial depolarization=
hyperexcitable membranes= hypocalemic tetany
hypocalcemic tetany is characterized by?
Starts where?
skeletal muscle spasms
- begin in extremities and progress to face and torso
- die of spasms to larynx
ECF Ca is utilized for cardiac muscle?
contraction
low plasma Ca = ______ cardiac contraction
weak
Ca is reuqired for many of the reaction that lead to what important function of blood?
blood clotting
why is stating that low plasma Ca compromises clotting theoretical?
because it would require an extreme drop in Ca to adversely affect clotting; person would MOST LIKELYDIE of HYPOCALCEMIC tetany first!!!
Ca is required for the formation of bone and ____>
teeth
Ca + HPO4 =
why is this structure important?
CaHPO4 aka hydroxyapatite
*larger, stronger and more insoluble than smaller compounds
where is 90% of body calcium located?
in bones and teeth
strength of inorganic vs organic components of mineralized tissue
- Inorganic= compressile strength
* Organic= tensile strength (collagen, elastin, glucopolysaccarharids
do we have more Ca or PO4 in blood? which one is more diffusable?
- more Ca in blood
* PO4 is more diffusible, that’s why you don’t have to keep much in blood
describe plasma calcium? diffusible or not?
- 10mg per day
- 40% bound to plasma proteins= NONdiffusible
- 50% free = Diffusible
- 10% nonionic calcium in complexes with citrate, phosphate, and bicarbonate= Diffusible
describe plasma phosphate (PO4)? diffusible or not?
- 4 mg per day
- 10% bound to plasma proteins= NONdiffusible
- 55% free= Diffusible
- 35% bound to Ca and other ions = Diffusible
we need ECF pyrophosphate to ______ of soft tissue
prevent mineralization
what does alkaline phaohatase do?
secreted by?
hydrolyzes pyrophosphate so mineralization can occur
*secreted by osteoblasts
most mineral exchange occurs between ____ and bone/teeth? which is diffusible and what isn’t?
ECF
- Ca and CaHPO4 is Diffusible
- hydroxyapatite is NONdiffusible (what we see in enamel)
where do we see exchange of minerals in teeth?
cementum (some with dentin at CEJ or pulp vessels)
what do osteoclasts do? derived from?
- derived from fused monocytes (multinucleated)
* function in bone resorption
osteoclasts secrete what 2 things to start resorption of bone?
1) hydrocholoric acid for demineralization of inorganic CaHPO4 to Ca and PO4
2) acid phosphatase enzyme to digest oragnic collagen matrix
osteoblasts are derived from? function in?
- derived from undifferentiated mesenchyme
* bone BUILDING/formation
osteoblats synthesize and secrete?
what gets imbed in the collagen matrix?
collagen and alkaline phosphatase to promote mineralization
*Ca++ and PO4 3- ions get imbedded in collagen matrix
osteoblasts become?
osteocytes
osteocytes derived from? function?
- derived from osteoblasts
* function in both bone resorption and bone formation
minerals are mobilized (destruction of bone) by?
osteoclasts or osteocytes
= resorption
minerals are deposited (formation of bone) by?
osteoblasts or osteocytes
= deposition
what is bone modeling? stops when? occurs where?
growing
- shapes bones during growth
- stops at age 18-20
- resorption and formation occur on different surfaces
Why is resorption on inner side and deposition on outside for bone modeling?
both need to happen and happen simultaneously to grow. If not, you’d get thick and heavy bones
what is bone remodeling? occurs when? occurs where?
repair or maturation of bone
- continuously occuring to repair microfractures
- resorption and formation occur sequentially at SAME SITE
bone modeling vs remodeling?
- modeling= resorption and formation occur sequentially on Opposite sides
- REmodeling= resorption and formation occur sequentially at SAME SITE
Remodeling cycle?
1) activation
- -osteoclasts formed by blood monocytes
2) resorption
- -dig hole via clasts
3) reversal
- -osteoclasts leaves and osteblasts comes in to form bone
4) formation
- -osteoblasts ONLY
