Renal 4 Flashcards
Tubular Reabsorption (3)
High capacity & variable; very selective Many electrolytes and nutrients almost completely reabsorbed Most waste products poorly reabsorbed.
Tubular Secretion (2)
Variable
Important for certain
electrolytes (K+, H+), drugs,
toxins.
Once fluid is reabsorbed across the tubule epithelium
into the interstitial fluid, it enters
peritubular capillaries
via Bulk Flow
Reabsorption =
Kf (Net Reabsorptive force)
= Kf (Reabsorptive Force)-(Filtration force)
=Kf ((πC + Pif) – (PC + πif))
Normal rate of Peritubular Capillary Reabsorption =
124 ml/min (GFR?)
Normal rate of Peritubular Capillary Reabsorption = 124 ml/min (GFR?)
Large: (2)
Large Kf (high surface area and permeability)
Large πC (due to volume lost during filtration)
> —% of filtered sodium
reabsorbed
99
> 99% of filtered sodium
reabsorbed
All along —
nephron
Sodium Reabsorption can
occur via both (2)
Transcellular
and Paracellular
Transcellular pathways (2)
- Passive across apical and active across basolateral membranes - Apical Na+ transport may be secondary active and tied to reabsorption of other substance (ex. Glucose)
Transport maximum
Maximum rate some substances
can be transported across the
epithelium (absorption or
secretion)
transport maximum is due to
saturation of transport
proteins
Renal Threshold is the
plasma
concentration that saturates the
carrier (tubular load)
Once the transport maximum is
reached for all nephrons,
further
increases in tubular load are not
reabsorbed and are excreted.
examples of transport max (6)
glucose, amino acids,
phosphate, sulfate, urate,
(creatinine, PAH)
As [Glucose] plasma increases, the [Glucose] filtrate —, Glucose tubular load —.
increases
increases
Reabsorption of Water: Passive But Influences Many Solutes
Strictly —
passive
As Na+ reabsorbed, creates
gradient for — reabsorption via
osmosis
H2O