Last edited: 11/21/2021
1. LOOP OF HENLE
Loop of Henle Medical Editor: Mariel Antoinette L. Perez
OUTLINE (3) Concepts
I) NEPHRON (i) Why does it get saltier?
II) LOOP OF HENLE Na+/K+/2Cl– Cotransporter
III) VASA RECTA o Transports sodium, chloride, and potassium from
IV) SUMMARY lumen of filtrate into tubule cell of ascending limb
V) APPENDIX
o There are specific channels for each ion in the cell
VI) REVIEW QUESTIONS
VII) REFRENCES Na+ and Cl– will be pushed out
• Increases osmolality (saltier)
Only some of the K+ leaks out, some of the K+
stays out
I) NEPHRON AfraTafreeh.com
• Some K+ gets pushed back in the lumen
Nephron is made of the following: o Creates depolarization of the inner side of
o Renal corpuscle the membrane of the ascending limb
Glomerulus Causes Mg2+ and Ca2+ to undergo
Bowman’s Capsule paracellular transport
Process: Glomerular Filtration Note the following:
o Proximal Convoluted Tubule o The descending limb of loop of Henle is completely
Processes impermeable to solutes
• Tubular Secretion o Exact opposite of the ascending limb which is only
• Tubular Reabsorption permeable to solutes, but impermeable to water
o Loop of Henle
o Distal Convoluted Tubule (ii) What happens due to the salty medullary
Each kidney has 1.2 million nephrons interstitial space?
o 2.4 million nephrons in two kidneys Counter-Current Multiplier Mechanism
o Water will flow out to the area where the salt is
II) LOOP OF HENLE From the descending limb to the ascending limb
Broken into two parts Due to obligatory water reabsorption
o Descending limb Via Aquaporin-I
AfraTafreeh.com • This is always open in the descending limb of
o Ascending limb
Loop of Henle
(A) OSMOLALITY o Since the medullary interstitial space is saltier as we
go down, more water will leave as we go down the
(1) Osmolality Classification
descending limb
Hypertonic o Hence, by the time the loop of Henle takes a turn to
o osmolality go up, its osmolality will be 1200 mosm
o solutes (e.g., Na+,Cl–), H2O Becomes hypertonic
Hypotonic o When it goes up, however, the osmolality starts to go
o osmolality down because the ascending limb is losing salt
o solutes (e.g., Na+,Cl–), H2O o By the time it reaches the Distal Convoluted Tubule,
osmolality will be around 120-200 mosm
Isotonic Becomes hypotonic to the plasma
o solutes = H2O
(2) Osmolality Values III) VASA RECTA
inside the glomerulus: ~300 mosm Peritubular capillary in the medulla
o blood plasma Branch of the Efferent Arteriole
Known as the “Counter-Current Exchanger”
In Bowman’s capsule: ~300 mosm Plasma Osmolality Gradient:
o Isotonic with the blood plasma o 300 500 700 900 1200
When it leaves the PCT: 300 mosm Blood flow to vasa recta is really slow
o Still isotonic with the blood plasma Function:
o It didn’t change because equal amounts of solutes o Prevents rapid removal of sodium chloride
and water were being reabsorbed Does not develop the medullary interstitial gradient
Due to obligatory water reabsorption or the counter-current multiplier mechanism
• E.g., 65% H2O, 65% Na+ It’s maintaining the gradient; not generating it
• Recall (from Ninja Nerd Proximal Convoluted o Carries Oxygen
Tubule lecture): obligatory water reabsorption Cells depend on oxygen
is the concept wherein water feels obliged to Vasa recta also delivers oxygen and nutrients
follow sodium.
o Isotonic with the blood plasma IV) SUMMARY OF LOOP OF HENLE
Medullary interstitial osmolality gets saltier or more Descending Limb
hypertonic as we go down the renal medulla o H2O permeable
o 300 mosm 500 mosm 700 mosm 900 mosm o Solute impermeable
1200 mosm o Aquaporin-I
LOOP OF HENLE RENAL PHYSIOLOGY: Note #3. 1 of 2
1. LOOP OF HENLE
Loop of Henle Medical Editor: Mariel Antoinette L. Perez
OUTLINE (3) Concepts
I) NEPHRON (i) Why does it get saltier?
II) LOOP OF HENLE Na+/K+/2Cl– Cotransporter
III) VASA RECTA o Transports sodium, chloride, and potassium from
IV) SUMMARY lumen of filtrate into tubule cell of ascending limb
V) APPENDIX
o There are specific channels for each ion in the cell
VI) REVIEW QUESTIONS
VII) REFRENCES Na+ and Cl– will be pushed out
• Increases osmolality (saltier)
Only some of the K+ leaks out, some of the K+
stays out
I) NEPHRON AfraTafreeh.com
• Some K+ gets pushed back in the lumen
Nephron is made of the following: o Creates depolarization of the inner side of
o Renal corpuscle the membrane of the ascending limb
Glomerulus Causes Mg2+ and Ca2+ to undergo
Bowman’s Capsule paracellular transport
Process: Glomerular Filtration Note the following:
o Proximal Convoluted Tubule o The descending limb of loop of Henle is completely
Processes impermeable to solutes
• Tubular Secretion o Exact opposite of the ascending limb which is only
• Tubular Reabsorption permeable to solutes, but impermeable to water
o Loop of Henle
o Distal Convoluted Tubule (ii) What happens due to the salty medullary
Each kidney has 1.2 million nephrons interstitial space?
o 2.4 million nephrons in two kidneys Counter-Current Multiplier Mechanism
o Water will flow out to the area where the salt is
II) LOOP OF HENLE From the descending limb to the ascending limb
Broken into two parts Due to obligatory water reabsorption
o Descending limb Via Aquaporin-I
AfraTafreeh.com • This is always open in the descending limb of
o Ascending limb
Loop of Henle
(A) OSMOLALITY o Since the medullary interstitial space is saltier as we
go down, more water will leave as we go down the
(1) Osmolality Classification
descending limb
Hypertonic o Hence, by the time the loop of Henle takes a turn to
o osmolality go up, its osmolality will be 1200 mosm
o solutes (e.g., Na+,Cl–), H2O Becomes hypertonic
Hypotonic o When it goes up, however, the osmolality starts to go
o osmolality down because the ascending limb is losing salt
o solutes (e.g., Na+,Cl–), H2O o By the time it reaches the Distal Convoluted Tubule,
osmolality will be around 120-200 mosm
Isotonic Becomes hypotonic to the plasma
o solutes = H2O
(2) Osmolality Values III) VASA RECTA
inside the glomerulus: ~300 mosm Peritubular capillary in the medulla
o blood plasma Branch of the Efferent Arteriole
Known as the “Counter-Current Exchanger”
In Bowman’s capsule: ~300 mosm Plasma Osmolality Gradient:
o Isotonic with the blood plasma o 300 500 700 900 1200
When it leaves the PCT: 300 mosm Blood flow to vasa recta is really slow
o Still isotonic with the blood plasma Function:
o It didn’t change because equal amounts of solutes o Prevents rapid removal of sodium chloride
and water were being reabsorbed Does not develop the medullary interstitial gradient
Due to obligatory water reabsorption or the counter-current multiplier mechanism
• E.g., 65% H2O, 65% Na+ It’s maintaining the gradient; not generating it
• Recall (from Ninja Nerd Proximal Convoluted o Carries Oxygen
Tubule lecture): obligatory water reabsorption Cells depend on oxygen
is the concept wherein water feels obliged to Vasa recta also delivers oxygen and nutrients
follow sodium.
o Isotonic with the blood plasma IV) SUMMARY OF LOOP OF HENLE
Medullary interstitial osmolality gets saltier or more Descending Limb
hypertonic as we go down the renal medulla o H2O permeable
o 300 mosm 500 mosm 700 mosm 900 mosm o Solute impermeable
1200 mosm o Aquaporin-I
LOOP OF HENLE RENAL PHYSIOLOGY: Note #3. 1 of 2
