Describe how a healthy kidney produces urine

At the Bowman's Capsule, the blood undergoes ultrafiltration. This is when the smaller molecules in the blood are forced through the partially permeable membrane of the Bowman's Capsule. This is because the beating of the heart causes there to be a higher pressure in the capillaries of the blood than the Bowman's Capsule. Water, urea, glucose, and ions (salts) are small enough to move across the partially permeable membranes. Proteins and red and white blood cells are too big to move across so remain in the blood. Along the Loop of Henle water moves via osmosis from a high concentration to a low concentration from the Loop of Henle to the blood capillaries. The same happens for ions which move via diffusion from a high concentration to a low concentration. So SOME of the ions and water are reabsorbed. All of the glucose is reabsorbed as it is moved against the concentration gradient through active transport (from low concentration to high concentration) which requires energy. Urea cannot move back across into the blood as the loop of Henle is not permeable to urea.

So overall:

Some water is filtered by the kidney, some ions are filtered by the kidney, urea is filtered by the kidney and glucose is not filtered by the kidney.