What Are Nephrons and What Do They Do?

Inside each of your kidneys are about one million tiny filtering units called nephrons. These microscopic structures are the real workhorses of the kidney, responsible for cleaning your blood and forming urine.

Each nephron has two main parts: the glomerulus and the tubule. The glomerulus is a cluster of tiny blood vessels that acts like a filter. Blood flows into the glomerulus, where water, waste, and small molecules are pushed out of the bloodstream. Larger molecules like proteins and blood cells stay in the blood, where they belong.

The filtered fluid—called filtrate—then enters the tubule, a long, twisting structure where the body fine-tunes what stays and what goes. Useful substances like glucose, certain salts, and water are reabsorbed back into the blood. What remains becomes urine, which is sent to the bladder for removal from the body.

Nephrons are incredibly efficient. Working together, they filter about 180 liters (48 gallons) of blood every day, adjusting fluid and chemical levels to match your body’s needs. If you drink more water, the nephrons help excrete the excess. If you are dehydrated, they conserve water by concentrating the urine.

There are two types of nephrons: cortical nephrons, which are found mostly in the outer part of the kidney, and juxtamedullary nephrons, which go deeper and help concentrate urine.

The function of nephrons is essential for removing waste, maintaining the right balance of salts and fluids, controlling blood pressure, and keeping your body in a steady state. Without them, your blood would quickly become overloaded with toxins and imbalances.

Understanding nephrons gives you a clearer picture of just how remarkable your kidneys really are—and why keeping them healthy is so important.

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