Info

glomerular filtration rate (GFR). The quantity of Na+ reabsorbed was calculated from the difference between filtered and excreted amounts. Note that 99.6% (25,100=25,200) of the filtered Na+ was reabsorbed or, in other words, percentage excretion of Na+ was only 0.4% of the filtered load. In terms of overall Na+ balance for the body, the quantity of Na+ excreted by the kidneys is of key importance because ordinarily about 95% of the Na+ we consume is excreted by way of the kidneys. Tubular reabsorption of Na+ must be finely regulated to keep us in Na+ balance.

Figure 24.8 shows the percentage of filtered Na+ reabsorbed in different parts of the nephron. Seventy percent of

Proximal convoluted 70% tubule

100%

Distal convoluted tubule „6%

100%

Distal convoluted tubule „6%

Convoluted Tubule And Loop Henle

Collecting duct

Loop of Henle

The percentage of the filtered load of Na4

reabsorbed along the nephron. About 1% of the filtered Na4 is usually excreted.

Collecting duct

Loop of Henle

1% Urine

The percentage of the filtered load of Na4

reabsorbed along the nephron. About 1% of the filtered Na4 is usually excreted.

filtered Na4, together with the same percentage of filtered water, is reabsorbed in the proximal convoluted tubule. The loop of Henle reabsorbs about 20% of filtered Na4, but only 10% of filtered water. The distal convoluted tubule reabsorbs about 6% of filtered Na4 (and no water), and the collecting ducts reabsorb about 3% of the filtered Na4 (and 19% of the filtered water). Only about 1% of the filtered Na4 (and water) is usually excreted. The distal nephron (distal convoluted tubule, connecting tubule, and collecting duct) has a lower capacity for Na4 transport than more proximal segments and can be overwhelmed if too much Na4 fails to be reabsorbed in proximal segments. The distal nephron is of critical importance in determining the final excretion of Na4.

Was this article helpful?

0 0
Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

Get My Free Ebook


Post a comment