6: Basic Renal Processes for Sodium, Chloride, and Water Flashcards
If you give a patient a hypertonic saline bolus, how does this affect its intracellular osmolality?
increases
water will shift from IC space to the EC due to the osmotic pull from the hypertonic saline in the IV space
If your patient has hemorrhagic gastroenteritis will large volume of vomiting and diarrhea, how does this affect its intracellular osmolality
Increases
vomitus and diarrhea is hypotonic - left-over osmoles increase the IV and interstitial osmolality and pull water from the IC space
If you give your patient a D5W infusion, how does this affect its IC volume?
increases - water will distribute evenly through IC and EC space
What percentages of sodium are rabsorbed in the proximal tubule, the loop of Henle and the distal convoluted tubules?
- 65%
- 25%
- 10%
compared to the filtered sodium load, what percentage remains in the final urine?
less than 1%
What are the major anions absorbed with sodium in the tubules to maintain electroneutrality?
- Chloride
- Bicarbonate
Where is most bicarbonate reabsorbed?
In the proximal tubules (90%)
What are the two sources of body water?
- water intake (drinking/eating)
- water production during carbohydrate oxidation
What are the 4 ways of bodily water loss?
- urination
- gastrointestinal losses
- exhalation
- skin evaporation
Is the luminal or basolateral membrane of tubular cells more permeable to water?
basolateral membrane
high number of aquaporines –> cytosolic osmolality close to that of the interstitium
describe the luminal water permeability of tubular cells in the following nephron segments:
* proximal tubules
* loop of Henle
* distal convoluted tubules
* collecting ducts
- proximal tubules - highly water permeable with aquaporines and permeable tight junctions - reabsorption here is isotonic
- descending thin loop of Henle early parts still very permeabel to water
- ascending thick loop of Henle relatively water impermeable - higher Na than water fraction reabsorbed –> tubular fluid leaving here will be hypotonic (osmolality 1/3 of plasma)
- distal convoluted tubules little to no water reabsorption/very low permeability
- collecting ducts permeability is highly variable and adjusted depending on body water status
What does obligatory water loss mean?
the minimum water needed to excrete sufficient amounts of urea, sulfate, phosphate, and other waste products
Why does starvation decrease one’s ability to survive without water?
- starvation leads to a catabolic state –> releases excess solutes and waste products –> increases the obligatory water loss
- If no food intake –> no water production from carbohydrate oxidation
- no protein intake –> not enough urea to achieve sufficient osmolality of the inner medullary interstitium
How is most Na reabsorbed on the apical/tubular side of the poximal tubular cells?
via the NHE-3 antiporter
Sodium-hydrogen-exchanger 3
Name 3 solutes that are reabsorbed in the proximal tubules and are sharing a symporter with Na
- Amino acids
- glucose
- phosphorous
How does Na exit the cell on the basolateral tubular cell membrane?
Na-K-ATPase
Na/HCO3- symporter