Final answer:
a. Filtration, reabsorption, and secretion.
The kidneys serve the body by filtration, reabsorption, and secretion. They filter blood to remove waste, reabsorb necessary substances, and secrete excesses to maintain the balance of water, salts, and other substances, which are essential for regulating blood pressure, blood volume, and pH levels within the body.
Step-by-step explanation:
Functions of the Kidneys
The kidneys serve the body primarily by filtration, reabsorption, and secretion. This complex process starts with filtering the blood of waste and excess substances. When blood goes through the kidneys, almost all solutes except for proteins are filtered out in a part of the kidney called the glomerulus by a process known as glomerular filtration. After filtration, the next step involves the renal tubules, where most of the filtered solutes are reabsorbed into the bloodstream in a step known as tubular reabsorption. Subsequently, additional waste products and excess ions are secreted back into the kidney's tubules in a process called tubular secretion. The collected filtrate, which has now become urine, is then sent down to the bladder and eventually out of the body through urination.
These renal functions are vital for maintaining the body's balance of water, salts, and other substances like glucose. The kidneys also play a crucial role in managing blood pressure, erythropoiesis, and maintaining the correct pH levels within the body. Moreover, through the release of renin, the kidneys have a significant regulatory impact on blood volume and pressure.