Renal Function 4 Flashcards
(55 cards)
Importance of Calcium:
- stabilizes the excitable cell membrane
- 2nd messenger for cell signaling
- essential for blood clotting
** Tight control of ECF calcium is essential
Importance of phosphate:
- component of many organic molecules
- store and release ATP in bonds
- protein phosphorylation control many intracellular processes
- urinary buffer
**Tight control of phosphate not essential
Mineral homeostasis:
- dietary intake and absorption
- distribution within body components (redistributed)
- excretion (primarily by kidney
bone, kidney, and intestine are together regulating?
inflow, outflow, and redistribution of calcium and phosphate between different body compartments
A physiological important component of Calcium?
Ionized calcium - 50% of Ca in blood
- free form is closely regulated
What affects bound calcium?
pH affects the amount bound to albumin
What influences complex calcium?
plasma phosphate
Where does Ca absorption occue?
upper small intestine
-inefficient process (only 20% absorbed)
What is the calcium binding protein in intestinal cells regulated by?
Vitamin D3
What happens if a lot of phosphate from the diet binds with calcium?
It stops it from being absorbed
Intestinal absorption of Ca is influenced by ?
active vitamin D
What type of tissue is bone?
active - because it remodels
osteclast:
resorb bone - release Ca and phosphate
osteoblasts:
responsible for new bone formation and its mineralization
bone turnover =
balance between resorption and formation
In the Kidney in calcium filtered?
Yes - both free and complex Ca is filtered
What % of Ca is reabsorbed in proximal tubule (passive reabsorption)?
70% -
What type of Ca reabsorption happens in the late distal tubule?
active reabsorption regulated by PTH
Does tubular secretion of Ca2+ occur?
no
When does uptake of phosphate happen in cells and why?
after feeding (insulin) - because insulin stimulates phosphate uptake in order to phosphorylate glucose
Phosphate is diet is absorbed by?
active transport stimulated by Vitamin D3
The more Ca in diet , the more MG, the more multivalent leads to
less available phosphate for absorption
What happens to phosphate when calcium is released from bone?
phosphate is also released
how much phosphate present in plasma is filtered?
around 90% - not much protein binding of phosphate