This chapter deals with nephron structure, electron microscopic structure of filtering surface, the three segments of the renal tubule namely the proximal convoluted tubule, the loop of Henle and the distal convoluted tubule are described in detail. Vascular arrangement in the kidney and the factors contributing for high pressure in the renal capillaries are discussed in detail. The difference in the vascular arrangement of juxta medullary nephrons from other nephrons is described. Chapter 2 deals with urine formation. The historical concepts of renal functions are mentioned at the beginning. Several processes involved namely glomerular filtration, tubular reabsorption, tubular secretion or excretion and tubular synthesis of new substances are discussed in detail. The renal handling of various plasma constituents are given in an elaborate manner. Chapter 3 deals with regulation of acid –base balance and osmotic equilibrium. After explaining the buffer systems of blood and other body fluids the role of kidneys in the regulation of acid base balance is discussed. The causes of acidosis, alkalosis are discussed. The role of the kidney in the regulation of osmotic equilibrium of the body fluids and how concentrated and dilute urine are formed is clearly explained. The mechanism of action of various diuretics is given adequately. Chapter 4 deals with endocrine functions of the kidney. Hormones produced by the kidney: Renin, Erythropoietin, 1-25-hydroxycholecalciferol and prostaglandins are described. The detailed structure of juxta medullary apparatus is given and its functions are given. Erythropoietin synthesis and its role are described. Hormones acting on kidney and their physiologic effects are discussed in detail. In this section chapter five, after describing the components of the urinary system the innervation of the urinary bladder by the parasympathetics and sympathetics nerves. The filling of the bladder and emptying of the bladder and nervous mechanisms influencing these processes are given clearly. Applied aspects related to urinary bladder are discussed. Tests for renal functions are given in detail. These are a brief mention about renal dialysis and kidney transplant. Chapter six deals with skin and its function: The structure of skin is discussed in detail. Sweat glands structure, it in innervation composition of sweat, mechanism of sweat secretion is given in detail. Functions of the skin are listed out and there is a detailed discussion on body temperature regulation. Clinical aspects related to body temperature: Heat stroke, Head cramp, fever are discussed.