The kidneys are highly vascularized organs that are responsible for maintaining the body's internal environment. The nephron is the basic structural and functional unit of the kidney involved in the complex interplay between tubular and vascular components resulting in the excretion of fluid and solutes. The regulation of body fluid and solutes is governed by the processes of filtration, reabsorption, and secretion. Unwanted fluid and substances are excreted from the body as urine.