What is tubular secretion?

What is tubular secretion?

• A. Secretes substances from the tubular fluid to the blood.
• B. Secretes substances from the blood back to the tubular fluid.
• C. Reabsorbs water from the tubular fluid.
• D. Filters blood to form urine.

Answer: (B)

Tubular secretion is the movement of substances from the blood into the tubular fluid within the nephron, typically via active transport in the tubular epithelium and peritubular capillaries. This process adds compounds like hydrogen ions, potassium, and certain drugs to the filtrate so they can be excreted in urine, and it helps fine-tune acid-base and electrolyte balance. It runs in the opposite direction of reabsorption (which moves from tubular fluid back to blood) and is distinct from filtration (which moves plasma from blood into the tubule to form filtrate). Thus, secreting substances from the blood back to the tubular fluid correctly describes tubular secretion.

Tubular secretion is the movement of substances from the blood into the tubular fluid within the nephron, typically via active transport in the tubular epithelium and peritubular capillaries. This process adds compounds like hydrogen ions, potassium, and certain drugs to the filtrate so they can be excreted in urine, and it helps fine-tune acid-base and electrolyte balance. It runs in the opposite direction of reabsorption (which moves from tubular fluid back to blood) and is distinct from filtration (which moves plasma from blood into the tubule to form filtrate). Thus, secreting substances from the blood back to the tubular fluid correctly describes tubular secretion.