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

Explanation

1. Tubular secretion is the passage of waste material from the blood to the filtrate in the Nephron. It is the last stage of Excretory process taking place in the Nephron.
2. Substances such as H+, K+, NH +, creatinine and organic acids move into the filtrate from the peritubular capillaries into the tubular fluid.
3. Most of the water is absorbed in the proximal convoluted tubule and Na+ is exchanged for water in the loop of Henle. Hypotonic fluid enters the distal convoluted tubule and substances such as urea and salts pass from peritubular blood into the cells of DCT.
4. The urine excreted contains both filtered and secreted substances. Once it enters the collecting duct, water is absorbed and concentrated hypertonic urine is formed.
5. For every H+ secreted into the tubular filtrate, a Nat is absorbed by the tubular cell. The H+ secreted combines with HCO,, HPO, and NH, and gets fixed as H,CO, H,PO, and NH, respectively. Since it gets fixed in the fluid, reabsorption of H+ is prevented.