How do nephrons filter blood to remove waste?

Nephrons filter blood by glomerular filtration, tubular reabsorption, and tubular secretion to remove waste and maintain homeostasis.

Nephrons, the functional units of the kidneys, play a crucial role in the filtration of blood and removal of waste products. This process involves three main steps: glomerular filtration, tubular reabsorption, and tubular secretion.

The first step, glomerular filtration, occurs in the glomerulus, a network of tiny blood vessels located at the beginning of the nephron. Blood pressure forces water, salts, glucose, and urea out of the blood and into the Bowman's capsule, a cup-like structure that surrounds the glomerulus. This filtrate, which is free of cells and proteins, then moves into the proximal convoluted tubule.

In the second step, tubular reabsorption, the filtrate travels through the proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule. During this journey, the walls of these tubules reabsorb nearly all of the water, glucose, and essential ions back into the bloodstream. This process is selective, meaning that the body can control what substances are reabsorbed based on its needs.

The final step, tubular secretion, involves the active transport of substances from the blood into the distal convoluted tubule. This step is crucial for the removal of waste products such as urea, creatinine, and certain drugs. It also helps to maintain the pH balance of the blood by secreting hydrogen ions.

In summary, nephrons filter blood by forcing it through the glomerulus, where water and small solutes are filtered out. The filtrate then travels through the tubules, where essential substances are reabsorbed and waste products are secreted. This complex process ensures that the body maintains a stable internal environment, free of harmful waste products.