What initial step occurs when unclean blood enters the kidneys?

When unclean blood enters the kidneys, the initial step involves the blood flowing through the renal arteries into the kidneys, where it then passes through a network of blood capillaries in the renal cortex. This is crucial for the filtration process, as the cortex contains the glomeruli, which are specialized structures that allow for the filtration of blood.

During filtration, waste products, excess salts, and water are removed from the blood as it passes through these capillaries, allowing for the formation of urine. This step is vital for maintaining the body’s fluid and electrolyte balance, as well as for detoxifying the blood. By starting in the cortex, the kidneys effectively begin their essential function of purifying the blood right away, making this initial step a fundamental part of renal physiology.