The kidneys in human beings are a part of the system for (a) nutrition. (c) excretion. (b) respiration. (d) transportation.

The kidneys play a crucial role in maintaining the body's overall health. They have several key functions that ensure our internal environment remains balanced. Their primary role is to filter blood and remove waste products. They also help in regulating the body's fluid and electrolyte balance. This is vital for maintaining stable levels of substances like sodium, potassium, and calcium.

Kidneys also help control blood pressure by managing the volume of fluids in the body and releasing certain hormones. They contribute to red blood cell production by releasing erythropoietin, a hormone that stimulates the bone marrow to produce more red blood cells.

• Filtering blood
• Removing waste products
• Regulating fluid and electrolytes
• Controlling blood pressure
• Supporting red blood cell production

One of the kidneys' most essential tasks is waste removal. Our body produces waste from various metabolic processes, and it needs to get rid of these wastes to prevent toxicity. The kidneys are adept at filtering out urea, creatinine, and other metabolic by-products from our blood.

This waste removal process involves three main steps: filtration, reabsorption, and secretion. During filtration, blood enters the kidneys, and substances are filtered out of the blood into the kidney’s nephrons. In the reabsorption step, useful substances like glucose and amino acids are reabsorbed back into the bloodstream. Finally, in the secretion phase, additional waste products are added to the filtrate, which later forms urine.

• Filtering out urea and creatinine
• Three-step process: filtration, reabsorption, secretion
• Maintaining blood purity

Urine production is a critical function of the kidneys. It allows the body to excrete liquid waste and maintain a stable internal environment. This process occurs in tiny functional units of the kidneys called nephrons.

The production of urine begins with the filtration of blood in the glomerulus, where water, salts, and waste products are separated from the blood cells and proteins. This filtrate then moves through the tubules of the nephron, where reabsorption and secretion occur, as described earlier.

The final product, urine, is collected in the renal pelvis and then passed down through the ureters to the bladder, where it is stored until excretion. Healthy urine production is essential for waste removal and maintaining the body's fluid and electrolyte balance.

• Begins in the glomerulus
• Filtrate moves through nephron tubules
• Reabsorption and secretion processes
• Urine collected in the renal pelvis
• Stored in the bladder