 Dear students, in this topic we shall discuss the anatomy of nephron of mammalian kidney. Nephrons are the functional units of kidney. The number of nephrons in kidneys of vertebrates vary. In lower vertebrates, each kidney has only several hundred nephrons, while in many small mammals, the number of nephrons is in some thousands. Humans and other large mammals have one million or more nephrons in one kidney. The nephron consists of two major units. One is the renal carpuscle and the other is a renal tubule. The renal carpuscle is an expanded part at the closed end of renal tubule. It is composed of a network of capillaries which is called glomerulus. The second part of renal carpuscle consists of a thin double-walled cup-shaped structure which is called Bowman's capsule and it surrounds the glomerulus. Glomerulus is responsible for ultrafiltration which is the first step in urine formation. The renal tubule leads away from Bowman's capsule. Its wall is only one cell thick. It has three portions, the proximal convoluted tubule, the loop of Henle and distal convoluted tubule. The first portion of renal tubule that is the proximal convoluted tubule is highly quiet. It dips into the medulla and forms a sharp loop of Henle. The loop of Henle has a descending limb and an ascending limb. Ascending limb returns to the level of renal carpuscle and coils to form distal convoluted tubule. This distal convoluted tubule is connected to a collecting duct. The glomeruli of nephrons lie in the renal cortex while the loop of Henle reached down into the papilla of medulla. These types of nephrons are found in radiating fashion in both the portions of the kidneys, in some parts of the cortex and in some parts of the medulla. Dear students, nephrons are two types of nephrons according to their size and particle and in the medullary portion, two types of nephrons are found, juxta medullary nephrons or cortical nephrons. Juxta medullary nephrons have their glomeruli in the inner part of cortex. Their loops of Henle are long, which plunge deep into the medulla. While the cortical nephrons glomeruli lie in the outer cortex. Their loops of Henle are relatively short and extend only a short distance into the medulla. Juxta medullary nephrons in tahai aham hote hain to produce concentrated urine in birds and mammals.