Tubular reabsorption part 2

Kidney tubule 1

 

Kidney tubule 2

 

SODIUM REABSORPTION (Na+)

Sodium ions (Na+) are the single most abundant cation in the filtrate, and about 80% of the energy is used for active transport is devoted to their reabsorption. Sodium reabsorption is almost always active and via the transcellular route.

In general, two basic processes that promote active Na+ reabsorption occur in each tubule segment. First, Na+ is actively transported out of the tubule cell by primary active transport-a Na+K+ ATPase pump present in the basolateral membrane. From there,  Na+ is swept along by the bulk flow of the water into adjacent  peritubular capillaries is rapid because the blood there has low hydrostatic pressure and high osmotic pressure (remember, most protein remain in the blood instead of being filtered out into the tubule).

Second, active pumping of Na+ from the tubule cells result in a strong electrochemical  gradient that favors its passive entry at the luminal face via secondary active transport carries  or via facilitated diffusion through channels. This  occurs because (1)the pump maintains the intracellular Na+ concentrations at low levels (2)the K+  pumped into the tubule cells almost immediately diffuses out into the interstitial fluid via leakage channels, leaving the interior of the tubule cell with a net negative charge.

Because each tubule segment plays a slightly different  role in reabsorption, the precise mechanism by which Na+ is reabsorbed at the luminal membrane varies.

Advertisements

About azaleaazelia

A nice person... :)
This entry was posted in Tak Berkategori. Bookmark the permalink.

One Response to Tubular reabsorption part 2

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s