The nephron is the structural and functional unit of the kidney. Each kidney, in a human, contains about one million nephrons. The nephron consists of a long tubule. Each nephron is composed of renal corpuscle and renal tubule.
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4.3.1 Functioning of Nephron and Urine Formation
Urea is the main nitrogenous waste material in the urine of man. Urea is formed in the liver and is carried to the kidney. The function of the kidney is to remove urea and form urine. It involves three processes in the nephron pressure or glomerular filtration, tubular or selective reabsorption and tubular secretion.
Glomerular filtration: It is the movement of small molecules across the glomerular wall as a result of blood pressure. When blood enters the glomerulus, blood pressure is sufficient to cause small molecules, such as water, nutrients, salts and wastes, to move from the glomerulus to the inside of the Bowman's capsule. The fluid that leaves the blood is called glomerular filtrate. Blood proteins and blood cells are too large to be part of this filtrate, so they remain in the blood.