What is the structure of a nephron in the kidney?

A nephron is the functional unit of the kidney, composed of a renal corpuscle, proximal convoluted tubule, loop of Henle, and distal convoluted tubule.

The nephron is a complex structure that plays a crucial role in the kidney's function of filtering waste from the blood and maintaining the body's fluid and electrolyte balance. Each kidney contains approximately one million nephrons, each of which is a self-contained unit for the production of urine.

The nephron begins with the renal corpuscle, which is made up of a network of capillaries called the glomerulus, enclosed in a cup-shaped structure known as the Bowman's capsule. The renal corpuscle is the site of blood filtration. As blood flows through the glomerulus, water, salts, glucose, and other small molecules are forced out of the blood and into the Bowman's capsule, forming a fluid known as filtrate.

The filtrate then flows into the proximal convoluted tubule, a twisted tube where most of the water and solutes are reabsorbed back into the blood. This process is largely driven by active transport, where cells use energy to move substances against a concentration gradient.

Next, the filtrate enters the loop of Henle, a long, U-shaped tube that extends into the medulla of the kidney. The loop of Henle plays a key role in maintaining the body's water and salt balance. As the filtrate flows down and then up the loop, water and salts are selectively reabsorbed, creating a concentration gradient in the surrounding tissue that helps the kidney produce concentrated urine.

Finally, the filtrate moves into the distal convoluted tubule, where further reabsorption and secretion of substances occur, fine-tuning the composition of the urine. The urine then flows into the collecting duct, which carries it to the renal pelvis and eventually out of the kidney.

In summary, the nephron is a complex structure that performs the essential functions of blood filtration, reabsorption, secretion, and urine formation in the kidney. Its intricate design allows it to efficiently remove waste products from the blood, while conserving vital substances and maintaining the body's fluid and electrolyte balance.