Urinary observations are made on the volume, colour, smell, deposits and specific gravity of the urine, and there are chemical tests for glucose, pH, protein, blood, bilirubin, urobilinogen, ketones, nitrite and leucocytes. The formation of urine is the role of the nephron, of which there are about 1 million in each of the two kidneys. Wastes, which are normally voided by the urinary system when the child is born, are excreted from the foetus via the placenta and then by the maternal urinary system. After birth, the kidneys are anatomically complete but remain underdeveloped and immature, and only reach maturity of function by 2 years of age. As a standard screening device, reagent strip urinalysis can be carried out as routine almost anywhere, and certainly on admission to hospital, pre-operatively, post-operatively, and in the outpatient clinic and the accident centre, where it can be used to help eliminate trauma to the kidneys.