Do the kidneys take out waste that are floating in blood?

The kidneys are essential organs in the human body responsible for filtering waste products and excess water from the blood, maintaining the body's fluid balance, and regulating blood pressure. The kidneys do not directly take out waste floating in the blood. Instead, they perform a complex process called filtration, reabsorption, and secretion to remove waste and regulate the composition of the body's fluids.

Here is an overview of how the kidneys work to remove waste from the blood:

1. Filtration: The kidneys receive blood from the renal arteries. As the blood enters the kidneys, it passes through tiny structures called nephrons, which are the functional units of the kidneys. Each nephron consists of several components, including the renal corpuscle and renal tubules. The renal corpuscle, which includes the glomerulus and Bowman's capsule, is responsible for filtering waste from the blood. Blood pressure forces the fluid component of the blood, along with waste products and electrolytes, into the Bowman's capsule. This filtrate contains substances like urea, creatinine, uric acid, excess water, electrolytes (sodium, potassium, chloride), and other waste molecules.

2. Reabsorption: As the filtrate moves through the renal tubules, essential substances like water, glucose, amino acids, and essential ions (sodium, potassium, bicarbonate, etc.) are reabsorbed back into the bloodstream. This process ensures that the body retains the necessary substances and prevents their loss through urine. Reabsorption occurs through active transport and passive diffusion mechanisms along the renal tubules.

3. Secretion: In addition to reabsorption, the renal tubules also actively secrete certain substances from the blood into the filtrate. These substances include hydrogen ions (H+), creatinine, drugs (certain medications), and other organic compounds that need to be eliminated from the body. By secreting these substances, the kidneys help maintain the body's pH balance and remove metabolic waste products.

The processed filtrate, now called urine, leaves the kidneys and flows into the ureters, which carry it to the bladder for storage. When the bladder is full, urine is expelled from the body during urination.

Therefore, while the kidneys do not directly take out waste that is floating in the blood, they perform the essential function of filtering, reabsorbing, and secreting substances to remove waste products and maintain the body's fluid and electrolyte balance.