5: Reabsorption of Salt & Water: Loop of Henle

Loop of Henle reabsorbs ≈..% of salt and water from the tubular fluid?

• 20%

The descending limb of the loop of Henle extends down into the?

• Medullary Tissue of the Kidney

Descending Limb is also called ?

• Nephron Loop

ascending loop comes back up into the renal cortex of the kidney and forms?

• Distal Convoluted Tubule

Water cannot be transported across the plasma membrane if the tubular filtrate?

• Surrounding Interstitial Fluid

• Is Isotonic

For water to be absorbed by osmosis the surrounding interstitial fluid must be?

• Hypertonic

The osmotic pressure of the interstitial fluid in the renal medulla is?

• 4x that of Blood Plasma

Interstitial fluid is the fluid that?

• Baths the cell bodies.

• it is one component of the extracellular fluid.

The descending and ascending limbs of the nephron loop are close enough..?

• To Interact

the movement of water and salt is not?

• Coupled

The interaction between the descending and ascending limbs creates a system known as the?

• Counter Current Multiplier System

Ascending Nephron Limb Diagram

The ascending limb of the nephron loop is composed of?

• 2 Segments

What are the 2 Segments of the Ascending Limb?

• Thin ascending limb which is nearest to the tip of the loop

• Thick ascending limb which brings filtrate to the distal convoluted tubule

NaCl is pumped out of the filtrate by the?

• Thick segment of the Ascending Limb

The basolateral membrane of the thick ascending limb epithelial cells are rich in?

• Na+ /K+ pumps.

• This ensures that Na+ concentration inside the epithelial cells is very low

Na+ enters the cell through a secondary active transporter that also functions to transport?

• k+ and CI- into the cell

• The ratio  =
  2 Cl- ,1 K+ , 1 Na+

The deeper regions of the medulla become extremely?

• Hypertonic

• concentrations of ≈1,200mOsm

concentrations of ≈1,200mOsm?

• Must remain trapped in the Medulla

The capillaries in the medulla are uniquely arranged so?

• So a High NaCl concentration can be maintained in the medullary interstitial fluid

The descending limb does not actively transport?

• Salt

• is impermeable to the passive diffusion of salt

However, the descending limb is permeable to?

• Water

• due to the presence of aquaporins in the apical membrane

Because the surrounding interstitial fluid of the medulla is very?

• Hypertonic

• Water is drawn out of the Filtrate Passively.

As more and more water leaves the filtrate, the filtrate itself becomes more?

• Hypertonic

the filtrate itself becomes more hypertonic the deeper the descending limb advances into the?

• Renal Medulla

At the tip of the loop, the hypertonic filtrate then passes into the?

• Ascending Limb

Filtrate in the descending limb flows deeper into the?

• Medulla

filtrate in the ascending limb flows in the opposite direction towards the?

• Cortex

Since the ascending and descending limbs are in such close proximity to each other, it allows?

• To Interact

The concentration of the filtrate in the descending limb is reflective of that of the surrounding?

• Interstitial Fluid

The concentration of this interstitial fluid is raised by the active?

• Active Extrusion of Salt

• from the ascending limb which receives it’s filtrate from the descending limb

The pumping of salt into the interstitium creates a

• Hypertonic Environment 

• in the medulla that draws water out of the descending limb filtrate creating a hypertonic filtrate

This hypertonic filtrate advances through into the ascending?

• Ascending Limb

• providing the ascending limb with a salt rich solution

The ascending limb beings to pump the salt from the hypertonic filtrate into the?

• Interstitium

• Making it even more Hypertonic

The vasa recta are long blood?

• Vessels that form the Efferent Arteriole

The Vasa Receta blood vessels run in parallel with the?

• Loop of Henle

• Serving as major blood vessels to the Renal Medulla

Vasa recta contain what making them water permeable?

• These blood vessels have aquaporins

This progression of the countercurrent multiplier system continues until the maximum concentration is reached in the?

• Inner Medulla

The vasa recta maintains hypertonicity within?

• Renal Medulla

As the vasa recta descend into the hypertonic medulla salt and urea moves into the?

• The blood whilst Water Moves out.

as the vasa recta ascend back towards the cortex the blood plasma is?

• Concentrated than the surrounding Interstitial Fluid

blood plasma is more concentrated than the surrounding interstitial fluid. As a result, the ascending vasa recta?

• Loose Salt and Urea

• Gaining Water

The active extrusion of NaCl into by the thick ascending limb of the nephron loop contributes the most to the?

• Hypertonic Solution of the Renal Medulla

The terminal portion of the collecting ducts contain?

• Urea Channels

. Urea can leave the collecting ducts deep in the inner medulla adding to the?

• Hypertonicity of Inner Medulla Interstitial Fluid