Vanders Renal Ch6 Flashcards
What are the approximate percentages of sodium reabsorbed in the major tubular segments?
65% in the proximal tubule, 25% in the thin and thick ascending limbs of Henle’s loop, 10% in the distal convoluted tubule and collecting-duct system
What are the approximate percentages of water reabsorbed in the major tubular segments?
Approximately 65% in the proximal tubule, varies in the loop of Henle, distal tubule, and collecting-duct system
Describe proximal tubule sodium reabsorption.
Involves apical membrane sodium entry mechanisms and basolateral Na-K-ATPase
Why is chloride reabsorption coupled with sodium reabsorption?
To maintain electroneutrality; the movement of sodium, a cation, must be accompanied by an equivalent movement of an anion
What are the maximum and minimum values of urine osmolality?
Maximum: 1400 mOsm/kg, Minimum: varies depending on hydration status
Define osmotic diuresis.
Increased urine output due to the presence of osmotically active substances in the renal tubules
Define water diuresis.
Increased urine output due to high water intake or low solute concentration
What is meant by obligatory water loss?
The minimum volume of water that must be excreted to eliminate waste products
Describe the handling of sodium by the descending and ascending limbs.
Sodium is not reabsorbed in the descending limb; reabsorbed in the ascending limb
What role do sodium-potassium-2 chloride symporters play?
They are involved in sodium transport in the thick ascending limb
How is water handled by the descending and ascending limbs?
Water is reabsorbed in the descending limb; not reabsorbed in the ascending limb
What does ‘separating salt from water’ refer to?
The ability to excrete either concentrated or dilute urine by independently controlling the reabsorption of solutes and water
How does antidiuretic hormone affect water and urea reabsorption?
Increases water reabsorption and promotes urea reabsorption in the collecting duct
What are the characteristics of the medullary osmotic gradient?
It allows for the concentration of urine and is generated by the thick ascending limb and urea recycling
What happens to the medullary osmotic gradient during water diuresis?
It is partially ‘washed out’ due to increased urine output and reduced solute concentration
What percentage of filtered sodium and chloride is reabsorbed in the proximal tubule?
About 65% of filtered sodium and more than 60% of filtered chloride
What is the main route of sodium excretion from the body?
Via the kidneys
What is the primary active transport mechanism for sodium reabsorption?
Na-K-ATPase pumps in the basolateral membrane
What is the primary source of body water?
Metabolically produced water and ingested water
What is insensible loss?
Continuous water loss through evaporation from the skin and respiratory passages
How does the kidney respond to a large water load?
Produces a large volume of very dilute urine
What is the role of aquaporins in water reabsorption?
Facilitate water movement across tubular cell membranes
What is the maximum urinary concentration the human kidney can produce?
1400 mOsm/kg
What is the significance of obligatory water loss?
It is necessary to excrete organic waste and varies with physiological states