Kidney tubule Coloured transmission electron micrograph TEM of a section through a proximal convoluted tubule in the kidney The proximal convoluted tubules function to reabsorb water glucose and other small molecules from the filtrate producing a concentrated urine The tubules consist of a lumen interior white lined with cuboidal epithelial cells green These cells are covered in many fingerlike projections known as microvilli which serve to increase the cells surface area for reabsorption The cells nuclei brown which contain the cells genetic information are also seen The reabsorbed molecules move into the interstitial fluid of the kidney and are absorbed back into the blood The liquid in the tubules passes to the bladder