Final answer:
The statement that nephrons perform the major work of urine formation is true as they filter blood, reabsorb necessary substances, secrete wastes, and convert filtrate into urine.
Step-by-step explanation:
The statement that the major work of urine formation is performed by the nephrons is true. Nephrons serve as the structural and functional units of the kidneys, with each kidney containing over a million of these tiny, intricate structures. The formation of urine by the nephrons involves several key processes, primarily glomerular filtration, tubular reabsorption, and tubular secretion.
Blood enters the kidney via the renal artery, which then leads to the glomeruli within the nephrons. There, blood plasma is filtered through a sieve-like structure formed by podocytes. The filtrate then proceeds through various segments of the nephron, where necessary substances are reabsorbed back into the bloodstream, and waste products are secreted into the filtrate. As it moves through the nephrontubules, it undergoes chemical changes to balance electrolytes and remove toxins, forming urine, which collects in the kidney and drains to the bladder through the ureter.