Physiology of the Genitourinary System I: Renal Blood Flow and Glomerular Filtration

The kidneys filter blood, remove waste, and maintain fluid balance.

They receive about 20-25% of the body’s blood supply, roughly 1200 mL per minute.

Blood enters each kidney through the renal arteries, branching off from the abdominal aorta.

These arteries then divide into smaller arterioles, leading to the afferent arterioles that supply blood to the glomeruli, the filtration units within the nephrons.

Blood pressure forces water and small solutes into Bowman’s capsule within the glomeruli, forming filtrate.

The glomerular filtration rate or GFR, about 125 mL per minute, indicates kidney function and is regulated by blood pressure and autoregulatory mechanisms.

Following this process, urine formation is carried out through three key steps: filtration, reabsorption, and secretion.

In the renal tubules, essential substances like water, glucose, and electrolytes are reabsorbed into the bloodstream, while waste products and excess ions are secreted into the tubules.

Then, finally, urine travels from the kidneys to the bladder through the ureters, ensuring that the body efficiently removes toxins and maintains homeostasis.