Question

What are the different stages in urine formation? Explain what happens in those stages.

Answer 1

Hint: Urine is formed in the kidneys of a human being. The urine is passed from kidney to bladder through the ureters. The urine is stored in the bladder. On urination, it is passed from bladder to urethra followed by excretion from the body.

Complete answer:
Urine is formed in the kidneys of a human being. The urine is passed from kidney to bladder through the ureters. The urine is stored in the bladder. On urination, it is passed from bladder to urethra followed by excretion from the body. There are three stages in the formation of urine. It includes:

> Glomerular filtration— It begins from here when the blood is filtered into the bowman‘s capsule through glomerulus. It results in the formation of glomerular filtrate. The afferent arteriole is wider than the efferent leading to increase in blood pressure. This filtrate is formed of all blood components with two exceptions i.e corpuscles and plasma proteins.

> Tubular reabsorption — when the filtrate comes to the proximal tubule all the essential nutrients get reabsorbed. These include glucose, amino acids, water, ions like sodium, potassium, chloride, bicarbonates, calcium and magnesium. The filtrate then moves to collect the duct. It reabsorbs excess water. This results in decreased urine volume.

> Tubular secretion — on reaching the proximal tubule, creatinine and uric acid are secreted in the filtrate along with potassium and small amounts of hydrogen ions.

Note: The average urine output for one day is 800-2000 ml. The normal pH of urine is 6.0 to 7.5 ie slightly acidic in nature but the normal range is 4.5 to 8.0. Urine is formed in the kidneys of a human being.