GMS 6401 STUDY GUIDE QUESTIONS AND
100% VERIFIED CORRECT ANSWERS!!
What kind of reabsorption is at the proximal tubule?
Iso-osmotic reabsorption (1:1 with Na+)
-Driven by solute reabsorption
How much water is reabsorbed at the descending Loop of Henle?
Reabsorbs ~10%
Water-permeable
Solute-impermeable --> tubular fluid becomes hyperosmotic
How much water is reabsorbed at the TALH and Distal Tubule?
-Impermeable to water
-Solute reabsorption continues --> tubular fluid becomes hypo-osmotic
How much water gets reabsorbed at the collecting duct?
-Water reabsorption depends on ADH
What happens if ADH is present?
Water is reabsorbed --> concentrated urine
What happens if ADH is absent?
Little water is reabsorbed --> dilute urine
What creates the medullary interstitial gradient?
-Countercurrent multiplication
-urea recycling
-enables water reabsorption from CD when ADH is present
The ability to create urine depends on...
,-Medullary interstitial gradient
-Tubular heterogeneity
- anatomy of medulla
tubular heterogeneity
different permeabilities to Na+, urea, and water in different segments
anatomy of medulla
tubules and vasa recta are arranged to maintain the intersitial gradient
When ADH is present....
-Increase H2O permeability in CD
-Water is reabsorbed down gradient
-decreased urine volume, increase osm
When ADH is not present...
-CD remains water-impermeable
-Water stays in tubule
-Increase urine volume, decrease osm
ADH=
Vasopressin = Arginine Vasopressin (AVP)
Intracellular (ICF)
high k+, low Na+ ; ~300 mosm/kg
Extracellular (ECF/plasma/intersitium)
High Na+, low K+ ; ~300 mosm/kg
Medulla (only exception)
Variable osmolality (up to ~1200 mosm/kg) due to concurrent processes
Water moves passively in all tissues to equalize osmolality, except
, in the renal medulla, where gradients are intentionally maintained
The ability to concentrate urine depends on:
-Medullary Interstitial Gradient
-Tubule properties
- Presence of Antidiuretic Hormone (ADH)
Medullary Interstitial Gradient
Gradient of increasing osmolality from cortex (~300) to papilla (~1200)
Tubule Properties
-Segment specific permeabilities to water, Na+, urea
-Precise anatomic arrangement of tubules and blood vessels in the medulla
Presence of Antidiuretic Hormone (ADH)
-ADH increases water and urea permeability in specific nephron segments
-Water reabsorption occurs only if tubular walls are permeable
What is the interstitial Osm at the cortex?
~300 mosm/kg
what is the interstitial Osm at the outer medulla?
~400-600 mosm/kg
What is the interstitial Osm at the inner medulla?
800-1200 mosm/kg (with ADH)
Tubular fluid entering the CD is always....
hypo-osmotic (~100 mosm/kg)
Osmotic gradient allows...
water reabsorption only if CD is water-permeable (via ADH)
descending limb (dLH)
100% VERIFIED CORRECT ANSWERS!!
What kind of reabsorption is at the proximal tubule?
Iso-osmotic reabsorption (1:1 with Na+)
-Driven by solute reabsorption
How much water is reabsorbed at the descending Loop of Henle?
Reabsorbs ~10%
Water-permeable
Solute-impermeable --> tubular fluid becomes hyperosmotic
How much water is reabsorbed at the TALH and Distal Tubule?
-Impermeable to water
-Solute reabsorption continues --> tubular fluid becomes hypo-osmotic
How much water gets reabsorbed at the collecting duct?
-Water reabsorption depends on ADH
What happens if ADH is present?
Water is reabsorbed --> concentrated urine
What happens if ADH is absent?
Little water is reabsorbed --> dilute urine
What creates the medullary interstitial gradient?
-Countercurrent multiplication
-urea recycling
-enables water reabsorption from CD when ADH is present
The ability to create urine depends on...
,-Medullary interstitial gradient
-Tubular heterogeneity
- anatomy of medulla
tubular heterogeneity
different permeabilities to Na+, urea, and water in different segments
anatomy of medulla
tubules and vasa recta are arranged to maintain the intersitial gradient
When ADH is present....
-Increase H2O permeability in CD
-Water is reabsorbed down gradient
-decreased urine volume, increase osm
When ADH is not present...
-CD remains water-impermeable
-Water stays in tubule
-Increase urine volume, decrease osm
ADH=
Vasopressin = Arginine Vasopressin (AVP)
Intracellular (ICF)
high k+, low Na+ ; ~300 mosm/kg
Extracellular (ECF/plasma/intersitium)
High Na+, low K+ ; ~300 mosm/kg
Medulla (only exception)
Variable osmolality (up to ~1200 mosm/kg) due to concurrent processes
Water moves passively in all tissues to equalize osmolality, except
, in the renal medulla, where gradients are intentionally maintained
The ability to concentrate urine depends on:
-Medullary Interstitial Gradient
-Tubule properties
- Presence of Antidiuretic Hormone (ADH)
Medullary Interstitial Gradient
Gradient of increasing osmolality from cortex (~300) to papilla (~1200)
Tubule Properties
-Segment specific permeabilities to water, Na+, urea
-Precise anatomic arrangement of tubules and blood vessels in the medulla
Presence of Antidiuretic Hormone (ADH)
-ADH increases water and urea permeability in specific nephron segments
-Water reabsorption occurs only if tubular walls are permeable
What is the interstitial Osm at the cortex?
~300 mosm/kg
what is the interstitial Osm at the outer medulla?
~400-600 mosm/kg
What is the interstitial Osm at the inner medulla?
800-1200 mosm/kg (with ADH)
Tubular fluid entering the CD is always....
hypo-osmotic (~100 mosm/kg)
Osmotic gradient allows...
water reabsorption only if CD is water-permeable (via ADH)
descending limb (dLH)
