The filtered blood is returned to the body through the veins. The fluid and its substances must now travel through a long and winding tubular pathway, first through the cortex, or outer portion of the kidney, then the medulla, the deep portion. There the tubule makes a sharp hairpin turn and travels back up to the cortex and its parent glomerulus. After looping through the cortex it connects to a collecting tubule and makes its final descent. The nephron is the combination of the filtering unit (glomerulus), its tubule and collecting duct. Together, they filter the blood, process the filtrate and make urine.