Lecture 18 - Water and the Kidney Flashcards
What percentage of TBW is found in the ICF (within cells)?
66%
What percentage of TBW is found in the ECF?
33%
What does ECF consist of (including %)?
Interstitial fluid (between cells) 75%
Plasma (solution in blood) 20%
Transcellular (inside epithelial lined spaces) 5%
What is the TBW in men vs women?
Men 60%
Women 55%
Which parts of the nephron are permeable to water?
Proximal Tubule
Thin Descending - Limb of Loop of Henle
Late Distal Tubule*
Collecting Duct*
*Under influence of Vasopressin (AVP)/ Antidiuretic Hormone (ADH)
Which parts of the nephron are not permeable to water?
Ascending Limb of Loop of Henle (Thin and Thick)
Early Distal Tubule (there is still debate about this)
Which of the following statements is TRUE?
A. 65% of a male’s body is composed of water.
B. Normally, a person has 4 litres of plasma in their blood.
C. The net water intake and water output of person per day is 0.
D. A person can live without water for 3 months.
C. The net water intake and water output of person per
day is 0 - when at homeostasis
What are aquaporins?
The aquaporin is a family of plasma membrane proteins that form channels that permit a high rate of water flow. They are specific to only water and they are impermeable to charged species.
How much water is reabsorbed in the PT?
67% - 120L of H2O per day
What epithelium is found in the PT?
Leaky absorptive epithelium
What is the movement of water in the PT?
Paracellular and transcellular
What AQP is found in leaky absorptive epithelium?
Aquaporin 1 (AQP1) which allows for the transcellular movement of water - present in both apical and basolateral membranes
How much water does the Thin Descending Limbs - Loop of Henle reabsorb?
16% - 30L of H2O
What epithelium is found in the thin descending limb of the loop of Henle?
Leaky absorptive epithelium
How much water does the late distal tubules reabsorb?
5-10% - 10-20L of H2O
What epithelium is found in the late distal tubules?
Tight absorptive epithelium
How much water does the collecting ducts reabsorb?
approx 8%
What epithelium is found in the CD?
Tight absorptive epithelium
What is the distribution of AQP in the LDT and CD?
AQP2 in the apical membrane
AQP3 and AQP4 in the basolateral membrane
Which AQP is under the regulation of AVP/ADH?
AQP2
Describe AQP2
AQP2 is found in the apical membrane of the LDT and CD or in vesicles. When ADH is released, the AQP2 found in the vesicles are incorporated into the membrane.
Which of the following statements is TRUE?
A. Aquaporins are only found in animals.
B. AQP2 is located on the apical membrane of Thick Ascending limb cells.
C. AQP3 is located in the basolateral membrane of collecting duct cells.
D. An osmotic gradient is NOT required for water movement.
C. AQP3 is located in the basolateral membrane of collecting duct cells.
Where is vasopressin (AVP)/anti-diuretic hormone (ADH) produced?
Produced in hypothalamus
- paraventricular nuclei
- supraoptic nuclei
What is the stimulus of release of AVP?
Increased body osmolarity (osmoreceptors)
Decreased plasma volume (baroreceptor reflex)
