Filtration and Urine Formation

The kidneys filter the blood several times a day via a multi step process performed mostly in the nephron, the main functional unit.

Starting in the renal corpuscle water and most solutes are filtered from the capillaries in the glomerulus into the surrounding Bowman's capsule. The pressure in blood vessels forces the filtrate into the capsule.

In the proximal convoluted tubule, or PCT some solutes are reabsorbed into the capillaries based on blood chemistry such as glucose, bicarbonates, and amino acids.

As the filtrate descends the loop of Henle more water is reabsorbed into the blood via aquaporin channels. This increases blood volume and pressure. On its ascending journey sodium and chloride ions are also reabsorbed.

When the filtrate arrives in the distal convoluted tubule, or DCT more waste products like creatinine and urea from the blood are secreted. Potassium, ammonium, and hydrogen ions are also removed to help adjust blood pH and electrolyte content.

Final solute and water adjustments are made in the collecting tubule which then moves the filtrate, purified as urine for pooling in the renal pelvis. Upon leaving the kidneys urine moves to the bladder and is excreted.