Nephron is the structural and functional unit of kidney. Each nephron consists of glomerulus and the renal tubule. Based on the length of Loop of Henle two types of Nephrons are seen. Cortical and Juxta-medullary nephrons. Cortical nephrons have short loop of henle as it extends in the cortex only and majority of nephrons are of this type. This type of nephron is mainly responsible for excretion function. Juxta medullary nephrons have long loop and extends in the medulla (Juxta means near). This is mainly responsible for concentration of urine so that water loss is prevented. This is done with the help of JGA i.e. Juxta Glomerular Apparatus. This includes Juxta Glomerular cells and Macula densa. The Juxta cells secrete Renin in response to low blood pressure and try to increase the blood pressure by RAAS (Renin Angiotension Aldosterone System).