Explain in detail how the nephron cleans the blood and returns it back to the body.

The nephron is the functional unit of the kidney and plays a crucial role in cleaning the blood and returning it back to the body. Here's a step-by-step explanation of how it works:

1. Filtration: The process begins in the renal corpuscle, which is made up of a network of capillaries called the glomerulus and a cup-shaped structure called the Bowman's capsule. Blood enters the glomerulus under high pressure, causing water, salts, glucose, and other small molecules to be forced out of the blood and into the Bowman's capsule. This mixture is called the filtrate. Larger molecules like proteins and blood cells are too big to pass through the glomerulus and remain in the blood.

2. Reabsorption: The filtrate then moves into the proximal convoluted tubule, where most of the water, salts, and glucose are reabsorbed back into the blood. This process is largely passive, meaning it doesn't require energy. The filtrate then moves into the loop of Henle, where more water and salts are reabsorbed. This process is active, meaning it requires energy.

3. Secretion: The filtrate, now much more concentrated, moves into the distal convoluted tubule. Here, additional substances that the body needs to get rid of, like potassium and hydrogen ions, are secreted from the blood into the filtrate.

4. Excretion: Finally, the filtrate, now called urine, moves into the collecting duct and then into the renal pelvis, where it is transported to the bladder for storage until it can be excreted from the body.

Throughout this process, the nephron is constantly adjusting the composition of the filtrate to maintain the body's balance of water, salts, and other substances. This is how the nephron cleans the blood and returns it back to the body.