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10 Cards in this Set

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  • Back
Where is phosphorous found in humans?
Most in bone ~85%
Soft Tissue ~14%
Blood ~1% (most free)
How is phosphorous absorbed? Where? How much?
Absorption occurs in the duodenum of SI. Active absorption via NTP2a transporter (co-absorption of Na); approximately 70% is absorbed (not dependent on dose) -- though stimulated by active D.
How is phosphorous homeostatis maintained? (general)
By renal excretion - urinary loss can fluctuate from 0.1-20%.
Within the kidney, where does this homestatis maintenance occur?
1. 90% of plasma phosphate is absorped by glomerulus
2. Reabsoption by the proximal tubule varies in response to phosphorous status (mediated by NTP2a)
Describe the mechanism by which phosphorous homeostasis is maintained: WHEN LOW
If phosphate status low: low dietary intake stimulates existing NTP2a co-transporters to TRANSLOCATE to apical membrane in proximal tubule. This increases reabsorption.
Describe the mechanism by which phosphorous homeostasis is maintained: WHEN HIGH
PTH stimulates NTP2a co-transported to be internalized, and this are degraded by lysosymes. Reabsorption decreases, excretion increased.
What are the metabolic functions of Phosphate?
Structure: mineral phase of bone (as hydroxyapatite)

And 3 main roles in soft tissues:
1. Phospholipids (membranes)
2. part of DNA/RNA
3. Metabolic intermediary: found in ATP, cAMP, many phosphorylated compounds
What are the causes of hypophosphatemia?
Low Phosphate: low dietary intake
1. Problems w/absorption
-disease of SI (crohns, celiac)
-malabsorption of D
2. High release rates
"anything that mucks up kidneys"
Excess urinary excretion
3. Antacids! Mg or Al complexes w/P
How is phosphate usually measured?
Serum phosphate levels
What are some deficiency signs?
1. Anorexia, lethargy
2. Nervous system impairment (both CNS/peri)
3. Osteomalacia/Rickets
4. Muscle weakness and breakdown