Collecting Ducts

The collecting ducts, which consist of cortical and medullary segments, reabsorb the final 5 to 7% of the filtered Na+. The epithelium forming the collecting ducts consists of two distinct cell types: principal cells and intercalated cells. The relative preponderance of the two cell types varies along the length of the collecting duct and between nephron segments. Principal cells are responsible for the reabsorption of Na+ and the secretion of K+ (Fig. 21.5). Na+ enters the principal cell from the tubular fluid through a unique and highly selective epithelial Na+ channel, ENaC. Intercalated cells reabsorb HCO3~ and K+ and secrete H+. Normally, H+ is secreted into the urine and HCO3~ is reabsorbed, while

Urine

principal cell

Blood

(filled circle)

intercalated cell

H4^ HCO3

10 Ways To Fight Off Cancer

10 Ways To Fight Off Cancer

Learning About 10 Ways Fight Off Cancer Can Have Amazing Benefits For Your Life The Best Tips On How To Keep This Killer At Bay Discovering that you or a loved one has cancer can be utterly terrifying. All the same, once you comprehend the causes of cancer and learn how to reverse those causes, you or your loved one may have more than a fighting chance of beating out cancer.

Get My Free Ebook


Post a comment