This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: Tubular secretion In contrast to tubular reabsorption, which returns substances to the blood, tubular secretion removes substances from the blood and secretes them into the filtrate. Secreted substances include H + , K + , NH 4 + (ammonium ion), creatinine (a waste product of muscle contraction), and various other substances (including penicillin and other drugs). Secretion occurs in portions of the PCT, DCT, and collecting duct. Secretion of H + . Because a decrease in H + causes a rise in pH (a decrease in acidity), H + secretion into the renal tubule is a mechanism for raising blood pH. Various acids produced by cellular metabolism accumulate in the blood and require that their presence be neutralized by removing H + . In addition, CO 2 , also a metabolic byproduct, combines with water (catalyzed by the enzyme carbonic anhydrase) to produce carbonic...
View Full Document
- Spring '10