ABSTRACT
RENAL (URINARY bladder and one urethra. The kidneys constantly filter the blood plasma (filtrate) through capillary networks called glomeruli and return most of the water and solutes back to the blood throughout the tiny filtering tubules called nephrons (see Figure 6.1). The waste products are excreted as urine, which consists of the excess water and solutes together with other wastes such as urea (a toxin to body cells), that is made from the breakdown of proteins and bilirubin (which gives urine its yellow colour) produced from the breakdown of red blood cell haemoglobin. The kidneys regulate blood minerals such as sodium and potassium, blood acidity within the normal pH 7.35-7.45 range and vascular pressure. They also produce two hormones: calcitol, which is activated vitamin D, that allows absorption of calcium from the gut for bone development; and erythropoietin, which stimulates the bone marrow to manufacture red blood cells when blood oxygen carrying capacity becomes low (Marieb and Hoehn 2007). The renal system is critical to the healthy function of all body systems.
