Final answer:
The nephron is the fundamental unit of the kidney that filters the blood and forms urine through glomerular filtration, tubular reabsorption, and tubular secretion. These processes ensure waste removal and the retention of necessary substances, with urine eventually expelled through the urethra.
Step-by-step explanation:
Nephrons: Essential for Urine Formation
The nephron is the functional unit of the kidney, critical for filtering blood and generating urine. The process involves three key functional processes: glomerular filtration, tubular reabsorption, and tubular secretion. These steps ensure that waste products are efficiently removed from the bloodstream while retaining necessary substances.
Glomerular Filtration
The first step occurs in the glomerulus, where blood pressure forces water, salts, glucose, amino acids, and other small molecules through the capillary walls, forming a filtrate while larger molecules and blood cells remain in the bloodstream.
Tubular reabsorption
As the filtrate flows through the renal tubules, essential nutrients and a significant amount of water are reabsorbed back into the bloodstream, leaving behind waste products.
Tubular Secretion
The last functional process occurs in the renal tubules as well, where additional wastes, excess ions, and drugs are actively removed from the blood and added to the forming urine.
Once formed, urine moves to the bladder via the ureters, is stored until urination, and is eventually expelled from the body through the urethra.
Beyond waste elimination, the urinary system also regulates blood volume and pressure, controls levels of electrolytes and metabolites, and regulates blood pH.