What are the main processes of urine formation ?

Explanation

Urine formation occurs in the kidneys involves the following steps:
i] Glomerular Filtration: Glomerular filtration is passive filtration of the blood that starts with entry of blood through glomerulus, a special ball of capillaries. The overall process leads to removal of 15-25% water and solutes from the plasma entering the glomerulus. Filtration of any substance through glomerular filtration depends on molecular size, protein binding, ionization, polarity, and working conditions of kidney in general.
ii] Tubular reabsorption: Glomerular filtrate enters the proximal convoluted tubule wherein nutrient and salt molecules are actively reabsorbed and pushed into the peritubular capillary network while water flows passively. The filtrate is now composed of urea, some salts and water.
iii] Tubular secretion: It includes active secretion of certain substances (`H+`, `K+`, ammonia, drug etc) from the peritubular capillary network into the distal convoluted tubule.
The urine formed is sent via ureter and gets collected in the urinary bladder temporarily for expulsion.