The outside section is called the Cortex while in interior is the medulla.the nephron is a made up of a cuplike structure at the top called to bowman's capsule it receives blood from the renal artery which supply the kidney with blood and filter the blood,body waste from the blood pass through the capsule down to structure called proximal convoluted tubule where water salts are reabsorb,down to loop of henle and to distal convoluted tubule.The ramaining waste is urine which pass out of the Henle's loop into ureter then to the bladder which stores urine and to urethra and is pass out of the body. The major function of the kidney is to excrete waste,they filter up to 1L of blood per day that's 36 times of the total volume of blood generate up to 3L of urine per day,what happens to the rest? Well that's where fitnesses of the kidney comes in, selectively reabsorbing useful materials even while getting rid of waste. Blood pressure control is intimately linked to the renal function.