4: Reabsorption of Salts and Water

The reabsorption of water from the nephron occurs?

• Passively through Osmosis

What allows the passive reabsorption of Water From the Nephron?

• the transportation of Na+ and Cl-

• across the tubule wall

The proximal tubule and loop of Henle reabsorb the majority of?

• Water & Salt from the Filtrate

however only 1-2L of?

• Urine is produced daily

Epithelial cells line the inner?

• Inner wall of the Nephron

Epithelial cells that line the Inner Nephron wall serve to filtrate?

• the lumen from the underlying connective tissues and vasculature.

epithelial membrane functions to?

• Reabsorb the Filtrate

The proximal tubule and nephron loop of Henle reabsorb ….%? of the filtrate?

• 85 of the Filtrate

In what Fashion do the Proximal Tubule and Nephron loop of the Henle absorb?

• constant unregulated fashion

What does “Constant Unregulated Fashion” mean?

• This means reabsorption happens at a constant rate

• and is not influenced by hormones or the autonomic nervous system etc.

Nephron Reabsorption Diagram

In cases of severe dehydration when the body needs to conserve water, only ?ml of urine is produced per day.?

• 400ML

• This is the minimum needed to excrete Metabolic Waste

The composition of the glomerular filtrate is almost identical to that of the?

• Of Blood Plasma

• Besides Plasma Proteins & Cells

The filtrate has an osmolarity of?

• 300 mOsm

The Filtrate and Blood Plasma are?

• Isomotic

Reabsorption of the filtrate cannot occur?

• Passively by Osmosis

Why can’t the Reabsorption of Filtrate occur passively by Osmosis?

• As very little concentration gradient exists between

• the filtrate and blood plasma

The Reabsorption of Filtrate thus requires what ?

• Active Transport of Na+

Proximal Tubule Reabsorption DIagram

Since the concentration of Na+ , K+ , glucose etc. in the filtrate of the nephron tubule is the same as the blood plasma what is required?

• Active Transports

• necessary to create a concentration gradient between the two fluid compartments

The apical surface of the epithelial cells contain?

• Microvilli

These microvilli function to?

• Increase the surface area of the Apical Membrane

• In contact with the filtrate of the proximal tubule

Microvilli allow?

• This allows for the greater diffusion of solutes across the apical plasma membrane

Apical Surface means?

• Surface facing the lumen.

The cytoplasm of proximal tubule epithelial cells has low?

• Na+

• Due to the Sodium Potassium Pumps on the basolateral membranes

The movement of Na+ down its concentration gradient drives?

• Reabsorption of Other Molecules

The movement of Na+ creates electro…?

• Electrostatic Gradient

• for transport of Cl- , so Cl follows Na+

The tight junctions of the proximal tubule are permeable to?

• To CI-,

• so not a lot of CI enters the Epithelial cell.

The majority of Clis reabsorbed from the filtrate by a?

• Paracellular Route

Glucose is able to enter the epithelial cells of the proximal tubule through the?

• Na+ -glucose cotransporters via a piggy-back mechanism

The Na+ -glucose is what type of Transport?

• Secondary Transport

glucose can only enter the cell because of the Na+ concentration gradient created by?

• the Na+ /K+ ATPase pumps

Approximately 65% of all water & salt in the filtrate is reabsorbed in the?

• Proximal Tubule

• At constant and unregulated rate

Glucose is only absorbed in the?

• Proximal Tubule