Loop of Henle by Ninja Nerd (Renal Physiology)

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