Question

Which segment is the site of secretion and regulated reabsorption of ions and pH homeostasis?

Answer 1

1. Distal tubule
2. Collecting duct
3. In the renal tubules H⁺ and NH⁴ are secreted and liberated into the tubules and excreted through
   urine thus maintaining acid-base balance.
4. For each H⁺ ions from the liberated filtrate one Na⁺ is reabsorbed in the tubules.
5. The secreted HCO₃, PO₃ and NH₃ combines to form carbonic acid and phosphoric acids.
6. Thus the H⁺ are maintained and their reabsorption is prevented.