The renal artery brings blood to the kidneys to\u00a0be filtered.\u00a0 Upon reaching a kidney, the renal artery branches into thousands of arterioles, each of\u00a0which leads to a nephron.\u00a0\u00a0A nephron is the basic working unit of the kidney; each\u00a0kidney may contain around\u00a0a million of them, according to\u00a0wikipedia<\/a>.<\/em><\/p>\n Upon entering the nephron, the blood\u00a0is spun at high speed in the glomerulus.\u00a0\u00a0The glomerulus is a\u00a0“merry-go-round”\u00a0of\u00a0capillaries.\u00a0\u00a0 Water, glucose, amino acids, ions, urea,\u00a0and uric acid\u00a0can pass\u00a0through it;\u00a0 the high speed flings them out.\u00a0\u00a0The solution thus expelled from the blood is called the filtrate.\u00a0 It enters the\u00a0convoluted tubule.\u00a0 This phase of kidney function is called glomerular filtration.<\/p>\n The main point of the kidneys is excretion, which means ridding the blood of nitrogenous wastes – chiefly urea and uric acid.\u00a0 Therefore, most of the filtrate now needs to be reclaimed.\u00a0\u00a0Virtually\u00a0all the glucose and\u00a0amino acids, most of the water, and some of the ions\u00a0are reabsorbed\u00a0by the peritubular capillary network\u00a0that surrounds\u00a0the convoluted tubule. \u00a0This phase of kidney function is called tubular reabsorption.<\/p>\n At the same time, certain\u00a0non-filtrable species (too big to exit the blood by glomerular filtration) are\u00a0actively\u00a0removed from the\u00a0capillary into the convoluted tubule.\u00a0 These non-filtrable species include drug remnants.\u00a0 Filtrable ions that escaped glomerular filtration can also be removed from the blood in this way.\u00a0\u00a0In either case, this phase of kidney function is called tubular secretion.<\/p>\n What remains of the filtrate after tubular reabsorption\u00a0– with the targets of tubular secretion\u00a0added in –\u00a0flows into the collecting duct, the ureter, and\u00a0finally into the urinary bladder.<\/p>\n There we have it:\u00a0 basic kidney function.\u00a0 It consists of three phases:\u00a0 filtration, reabsorption, and secretion.\u00a0 Of course, you can\u00a0read further.\u00a0\u00a0I use Sylvia S. Mader’s Inquiry into Life<\/em>, 11th edition, McGraw-Hill.<\/p>\n I hope this gets you started, anyway:)<\/p>\n