The important physiological function of the kidney includes glomerular filtration, reabsorption of solutes, secretion of extra ions and concentration or dilution of urine as per need of the body. The kidney helps in regulation of blood composition and volume by glomerular filtration. In filtration, pressure forces fluid and all solutes smaller than a certain size through a membrane. Filtration occurs in the renal corpuscles of the kidneys across the endothelial-capsular membranes. The resulting fluid that enters the capsular space is called glomerular filtrate. The fraction of plasma in the afferent arterioles of the kidneys that becomes glomerular filtrate is termed the filtration fraction. In the glomerulus, blood filtering depends on three main pressures, one that promotes filtration and two that oppose filtration. The ability of kidneys to maintain a constant blood pressure and GFR despite changes in systemic arterial pressure is called renal autoregulation.