Describe how a nephron works.

By filtering out everything in the blood, except for large proteins and blood itself. Then the distal and proximal tubule will slowly bring back in what the body needs, like calcium, chloride, etc and whatever is left goes to the ureter and gets to the bladder to be urinated out. The nephron capsule filters urea, water, glucose, and salts from the capillary, and sends them through the tubule. The tubule re-absorbs water and glucose back into the blood, and carries what is left over (urine, a mixture of urea, water, and salts) to the ureter. Nephron is the basic unit of Kidney, it has basically three parts: Glomerular capsule, Henle's loop, and Collection tube. Collection of nephron plays an important role in the excretory system.

http://science.howstuffworks.com/environmental/life/human-biology/kidney1.htm

http://www.purchon.com/biology/kidney.htm