What is the Difference Between Filtration and Reabsorption?

Filtration and reabsorption are two crucial steps in urine formation within the kidneys. They differ in their functions and the substances they involve:

Filtration:

• Involves the transfer of soluble components, such as water and waste, from the blood into the glomerulus.
• About 20% of the total blood pumped by the heart each minute enters the kidneys to undergo filtration.
• Filtration occurs in the glomerulus, where filterable blood components move towards the inside of the glomerulus, while non-filterable components exit via the efferent arteriole.

Reabsorption:

• Involves the absorption of molecules, ions, and water that are necessary for the body to maintain homeostasis from the glomerular filtrate back into the blood.
• Reabsorption occurs in the renal tubule, where nutrients and water are reabsorbed into capillaries.
• The primary function of reabsorption is to regulate blood volume and plasma osmolarity.

In summary, filtration is the process by which soluble components are transferred from the blood into the glomerulus, while reabsorption is the process by which essential molecules, ions, and water are absorbed back into the blood from the glomerular filtrate. These processes work together with secretion to form urine and maintain the body's overall homeostasis.

Comparative Table: Filtration vs Reabsorption

Here is a table summarizing the differences between filtration and reabsorption:

Both filtration and reabsorption are crucial steps in urine formation, taking place in the nephrons of the kidneys. Filtration occurs first, where blood filters inside the renal capsule to form the glomerular filtrate. Reabsorption follows, during which necessary nutrients and water are reabsorbed back into the bloodstream. Unlike filtration, reabsorption is selective, ensuring that only waste and excess water are removed from the body.