Question

Describe urine in relationship to glomerular filtration, tubular reabsorption and tubular secretion.

• A. GF – TR – TS
• B. GF + TR + TS
• C. GF + TR – TS
• D. GF – TR + TS

Answer 1

The correct option is D GF – TR + TS

Steps of urine formation:
(1). Glomerular Filtration (GF): The first step of urine formation is the filtration of blood, which is carried out by the glomerular capillaries. The glomerular filtration rate (GFR) is 125ml/min or 180 Litres/day.
(2). Tubular Reabsorption (TR): Volume of glomerular filtrate formed per day is 180 litres but volume of urine released is about 1.5 liters per day mean 99 percent of filterate reabsorbed by the different segments of nephrons, this process is called reabsorption.
(3). Tubular Secretion (TS): This is the last step of urine formation in which epithelial cells of renal tubules secretes excretory substance from the blood of peritubular capillary into the filtrate.

So, it can be concluded that urine formation=GF – TR + TS.