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10 Cards in this Set
- Front
- Back
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Where is phosphorous found in humans?
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Most in bone ~85%
Soft Tissue ~14% Blood ~1% (most free) |
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How is phosphorous absorbed? Where? How much?
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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.
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How is phosphorous homeostatis maintained? (general)
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By renal excretion - urinary loss can fluctuate from 0.1-20%.
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Within the kidney, where does this homestatis maintenance occur?
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1. 90% of plasma phosphate is absorped by glomerulus
2. Reabsoption by the proximal tubule varies in response to phosphorous status (mediated by NTP2a) |
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Describe the mechanism by which phosphorous homeostasis is maintained: WHEN LOW
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If phosphate status low: low dietary intake stimulates existing NTP2a co-transporters to TRANSLOCATE to apical membrane in proximal tubule. This increases reabsorption.
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Describe the mechanism by which phosphorous homeostasis is maintained: WHEN HIGH
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PTH stimulates NTP2a co-transported to be internalized, and this are degraded by lysosymes. Reabsorption decreases, excretion increased.
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What are the metabolic functions of Phosphate?
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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 |
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What are the causes of hypophosphatemia?
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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 |
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How is phosphate usually measured?
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Serum phosphate levels
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What are some deficiency signs?
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1. Anorexia, lethargy
2. Nervous system impairment (both CNS/peri) 3. Osteomalacia/Rickets 4. Muscle weakness and breakdown |
