16.7 Physiology: Kidney function, fluid and electrolyte balance Flashcards
What are the volumes and osmolarities for:
Bowman’s capsule
End of proximal tubule
End of loop of Henle
End of collecting duct (final urine)
Bowman’s: 180L/day, 300mOsM
End of proximal tubule: 54L/day (300mOsM)
End of loop of Henle: 18L/day, 100 mOsM
End of collecting duct: 1.5L/day, 50-1200 mOsM
What is the innermost part of the kidney? (also where kidney meets ureters)
The papilla (and major/minor calyces)
Which part of the kidney is the ‘workhorse’?
Proximal tubule
What is the concentration of the fluid at the junction of the cortex and medulla?
Isoosmotic fluid, 300mOsM
What are the membranes of the epithelial cell? What membranes does stuff getting absorbed cross?
Luminal and basolateral membrane (into the interstitial fluid)
Anything absorbed crosses luminal then basolateral membrane
What is an important property of the descending limb?
Permeability to water (aquaporins) and impermeability to everything else
What is the normal Urea concentration?
What is its concentration in the loop?
5mOsM
Loop: 20mOsM
What is the permeability of the ascending limb?
High sodium permeability (out of the tubule) low water permeability
What is an important property of thick ascending limb?
Lot of sodium reabsorbed, no water reabsorbtion
What is reabsorbed in the limbs/loop of Henle more? Water or sodium?
Sodium is reabsorbed more (dilute at the macular densa)
Which part of the nephron is called the diluting segment?
The ascending limb
What is the regulator of water balance and excretion?
Collecting duct
What does the ability to concentrate depend on? What is this controlled by?
Depends on number of aquaporins, controlled by ADH (vasopressin)
What does a high level of ADH do?
Inserts aquaporins, takes water out of collecting duct
What is a test we can use to determine if someone is in chronic renal failure?
Why?
Specific gravity: 1.010 (same as plasma)
Kidney has lost ability to concentrate and dilute, excretes a barely modified form
What are the ways that the following are reabsorbed?
Na+
Anions
H2O
K+,Ca2+, urea
Na+: active transport
Anions: electrochemical gradient
H2O: Osmosis (following solute)
K+, Ca2+, urea: permeable solutes by diffusion (concentration of other solutes increases as fluid volume in lumen decreases)
What proportion of oxygen consumed by the kidney does active transport account for?
80% of oxygen consumed by the kidney
What is active transport tied to the reabsorption of?
Water, chloride
Glucose, aas, urea
What is active transport tied to the secretion of?
K+
H+
Where does sodium/potassium exchange occur?
Basolateral membrane (Sodium out, potassium in)
Where are the Na/H and the Na/HCO3 exchange locations?
Na/H: apical
Na/HCO3: basolateral
Which way can the high intracellular concentration of potassium flow?
Only into the interstitium
