MECHANISM OF URINE FORMATION

MECHANISM OF URINE FORMATION

The process of urine formation in the body involves three process steps such as Filtration, Reabsorption and Secretion.

1.      Filtration

Filtration takes place in the glomerulus when the kidneys receive blood contents under high pressure through renal artery. In the glomerulus, filtration of amino acid, water, salt, glucose, and urea from the blood is done. At glomerulus, blood speed slow down to allow more absorption of materials. This is called glomerular ultra filtration.

2.      Reabsorption

Reabsorption is the movement of substances out of the renal tubules back into the blood capillaries. It occurs in different parts of the nephron such as proximal convoluted tubes, loop of Henle, distal convoluted tube and collecting duct.

i.        Reabsorption at proximal convoluted tube

In this region, Glucose, amino acid, potassium and calcium ions are reabsorbed

   ii.    Reabsorption at loop of Henle

In descending part of loop of Henle, water is reabsorbed while in ascending part loop of Henle, sodium ions are reabsorbed.

   iii Reabsorption at Distal convoluted tube

In this region, Sodium ions and water also are reabsorbed.

   iv Reabsorption at collecting duct

In this region, more water are absorbed

3.      Secretion

The process where substances move out of the blood into the renal tubules (nephron).Secretion takes place at distal convoluted tubule where potassium and acid in the form of hydrogen ions, are removed from the blood by the distal convoluted tubule, and are then added to the urine. 

URINATION

Is the release of urine from the urinary bladder through the urethra to the outside of the body. It’s the urinary system form of excretion.

COMPOSITION OF URINE

ü  Water

ü  Urea

ü  Salt eg sodium chloride

ü  Creatinine