Question

What is tubular secretion? Name the substances secreted through the renal tubules.

Answer 1

Tubular secretion is the transfer of materials from peritubular capillaries to the renal tubular lumen; it is the opposite process of absorption. This secretion is caused mainly by active transport and passive diffusion. Renal secretion is different from reabsorption because it deals with filtering and cleaning substances from the blood, rather than retaining them. 

The substances that are secreted into the tubular fluid for removal from the body include:

1. Potassium ions (K+)
2. Hydrogen ions (H+)
3. Ammonium ions (NH4+)
4. Creatinine
5. Urea. 

Answer 2

The movement of substances such as H⁺, K⁺, NH₄⁺, creatinine and organic acids from the peritubular capillaries into the tubular fluid, the filtrate is called Tubular secretion.