Caption

Kidney. Coloured light micrograph of a section through a kidney. Kidneys are part of the urinary system, filtering waste products, such as urea, from the blood and excreting them as urine. Their structure consists of an outer cortex (green), an inner medulla (orange, centre) and a renal pelvis (brown, left). The cortex contains glomeruli, coiled structures that filter the waste products from the blood. The medulla contains renal pyramids, structures that contain many tubules and ducts that carry the urine from the glomeruli to the renal pelvis. The renal pelvis acts as a funnel and directs the urine into the ureter. Magnification: x18 when printed 10cm wide.