Question

How does glomerular filtration occur?

Answer 1

The pressure gradient forces the fluid in the blood to get filtered from the bunch of capillaries in the glomerulus. Glomerular filtration is the first step of urine formation and it takes place in kidneys.

Complete answer:
The nephron is the structural and functional unit of the kidney and the glomerulus is one of the key structures of the nephron. The nephron has two important parts: renal corpuscle and renal tubule. The renal tubule consists of a bunch of capillaries called glomerulus and a bowman’s capsule surrounding it. The glomerulus has small slits or pores which allows the solutes to pass through it.

The first process of urine formation is glomerular filtration or also known as renal filtration. The blood enters the glomerulus through the afferent arteriole and leaves through the efferent arteriole. The diameter of the afferent arteriole is more than the efferent arteriole which results in the development of a pressure gradient in the glomerulus.

This increase in pressure forces the water and solutes like glucose, salts, and urea out of the capillaries as glomerular filtrate. The large blood cells and other proteins are not able to pass through the small slits of the capillaries so they continue to the efferent arterioles.

The filtrate containing water and small solutes will enter Bowman’s capsule after leaving the glomerulus.

Only water and smaller solutes can pass through the mesh-like slits of glomerulus but blood cells and proteins cannot pass and move out through the efferent arteriole.

Note: The total filtrate formed by the renal corpuscles in both kidneys per minute is called the glomerular filtration rate (GFR). The increase in GFR will increase urine production while the decrease in GFR will decrease urine production. The pressure gradient in the glomerulus will try to decrease GFR.