Explain the mechanism of tubular secretion explain its importance in the urine formation process?

Answer 1

"Tubular secretion is the reverse process of tubular reabsorption. Substances such as hydrogen and potassium ions and creatinine move either from the blood of the peritubular capillaries through the tubular cells or from the tubular cells into the filtrate to be disposed of in the urine. This process is important for the disposal of substances not ready in the filtrate and as a device for controlling blood pH"

Page 615 in Human Anatomy & Physiology Laboratory Manual

Answer 2

Urine is formed through three processes that occur in the kidney:

• Ultrafiltration, where almost all the blood components are filtered by the kidneys except for the blood cells and the plasma proteins, e.g. urea, water, sodium, glucose, potassium, ...etc.
• Selective reabsorption, where the essential components are reabsorbed back into the blood vessels, e.g. glucose, water, sodium, ...etc.
• Secretion, where, e.g. potassium is secreted by cells in exchange for another useful component, e.g. sodium in that case.
• Then the water reabosprtion content is further regulated before exiting the kidney through a hormone known as ADH.
• Urine is then formed, collected in the bladder and excreted outside the body later on