If you stretched the nephrons in a kidney they would be over forty miles long from end to end explain how this structure directly relates to the function of a kidney

A nephron is the basic structural and functional unit of the kidney. Its functions are to regulate the concentration of water and soluble substances like sodium salts by filtering the blood, reabsorbing what is needed and excreting the rest as urine. A nephron eliminates wastes from the body, regulates blood volume and blood pressure, controls levels of electrolytes and metabolites, and regulates blood pH. Its functions are vital to life and are regulated by the endocrine system by hormones such as antidiuretic hormone, aldosterone, and parathyroid hormone. In humans, a normal kidney contains 800,000 to 1.5 million nephrons, we have so many because we need them