Describe the process of urine formation in kidneys.

Urine formation

1. From the human body, waste is excreted in the form of urine.
2. Urine formation is carried out in three phases:
   • Glomerular filtration
   • Reabsorption
   • Secretion

Steps involved in urine formation in kidneys:

I) Glomerular filtration

1. Glomerulus filtration occurs in the glomerulus.
2. The process occurs across three layers-
   • Epithelium of Bowman's capsule.
   • Endothelium of glomerular blood vessels.
   • The membrane between two layers.

II) Reabsorption

1. Reabsorption is achieved by active and passive transport.
2. 99% filtrate is reabsorbed by the renal tubules.

III) Urine

1. Urine produced- 95% water and 5% nitrogenous wastes.
2. Wastes such as urea, ammonia, and creatinine are excreted in the urine.