TF/Px ratio and TF/Pinulin
Videos
Notes
Physiology
Renal system
Anatomy and physiology
Fluid compartments and homeostasis
Renal clearance, glomerular filtration and renal blood flow
Renal tubular reabsorption and secretion
Renal tubular physiology
Renin-angiotensin-aldosterone system
Renal electrolyte regulation
Renal sodium and water regulation
Renal endocrine functions
Acid-base physiology
High Yield Notes
10 pages
![TF/PX RATIO & TF/PINULIN osms.it/TF_Px-ratio-TF_Pinulin [TF/P]x RATIO ▪ Refers to concentration of substance (X) in tubular fluid (TF) and plasma (P) at given point in nephron Helps determine substance net secretion/ absorption ▪ [TF/P]x = 1 ▫ X: not reabsorbed/secreted (e.g. freely filtered) ▫ X: reabsorbed in proportion to water ▫ E.g. [TF/P]glucose = 1 when glucose, water reabsorbed equally in Bowman’s space ▪ [TF/P]x < 1 ▫ X: reabsorbed more than water ▫ E.g. [TF/P]glucose < 1 when glucose reabsorbed more than water along proximal tubule ▪ [TF/P]x > 1 ▫ X: reabsorbed less than water/X secreted into tubular fluid ▫ E.g. [TF/P]urea > 1 in presence of antidiuretic hormone (ADH) at collecting ducts (water reabsorbed, not urea) 538 OSMOSIS.ORG [TF/P]INULIN ▪ Inulin (inert substance—neither reabsorbed nor secreted) concentration throughout nephron helps determine how much is reabsorbed ▪ Inulin concentration will ↑ as water is reabsorbed ▪ Determined using this formula: Fraction of filtered water reabsorbed = 1− 1 [TF / P]inulin ▫ Fraction of filtered water reabsorbed = 1 - 1/2 = 0.5 (50%) ▫ [TF/P]inulin = 2 when 50% of water is reabsorbed (inulin concentration doubles) ▪ Double ratio formula determines fraction of filtered load of substance in nephron at any point [TF / P]x [TF / P]inulin ▪ If [TF/P]Na+ divided by [TF/P]inulin = 0.3, then 30% sodium remains in tubule, 70% reabsorbed](https://d16qt3wv6xm098.cloudfront.net/L272LWS3SrahYiiIaLaPomHaQoONCbuR/thumb-6.jpg)
External Links
