 Dear students, in this topic we shall discuss the anatomy of mammalian kidney. The kidneys of mammals are reddish-brown, bean-shaped, osmoregulatory organs. The lateral surface of a kidney is convex, while the medial side is deeply concave. This concave side forms a medial depression which is called hyalus or hyalum. Through the hyalus, renal artery and nerve enter and renal vein and ureter exit. Kidney is divided into two functional layers which contain the functional urine-forming units that is nephrons. The outer layer is called the renal cortex, while the inner layer is called the renal medulla. Renal medulla has a number of cone-shaped renal pyramids. The base of each pyramid is located at the boundary of renal cortex and renal medulla, while the tips of these conical pyramids are called renal papillae. Renal papillae are pointed toward the center. The parts of cortex also project between the renal pyramids. These parts are called renal columns. Renal columns are called minor calyx. Minor calyxes form a funnel-shaped structure which is called major calyx and make major calyx into major calyx. Major calyxes converge and make a large and large channel called renal pelvis. Urine is formed in the nephrons located in the renal pyramids. The tips of renal pyramids that is renal papillae open through minor openings through which urine exits from the nephrons into the major calyxes into the minor calyxes and from minor calyxes it moves into the major calyxes. Urine is collected in the renal pelvis from where it exits the kidney through a ureter.