How does tubular secretion help in maintaining ionic and acid-base balance in body fluids?

Tubular secretion:

In the process of urine formation, the tubular cells secrete substances like $H^{+},K^{+}$ and ammonia into the filtrate. Tubular secretion performed by Proximal Convoluted Tubule (PCT), Distal Convoluted Tubule (DCT), and Collecting Ducthelps in the maintenance of the ionic and acid-base balance of body fluids.

Proximal Convoluted Tubule(PCT):
PCT maintains the pH and ionic balance of the body fluids by selective secretion of hydrogen ions, ammonia and potassium ions into the filtrate and by absorption of $HC{O}_3^{–}$ from it.

Distal Convoluted Tubule (DCT):

DCT performs reabsorption of $HC{O}_3^{–}$ and selective secretion of hydrogen and potassium ions and $N{H}_3$ to maintain the pH and sodium-potassium balance in the blood.

Collecting Duct:

A collecting duct is a long duct that reabsorbs large amounts of water to produce concentrated urine. It helps in the maintenance of pH and ionic balance of blood by the selective secretion of $H^{+}$ and $K^{+}$ ions.