After water and other substances leave the surface of the renal tubule, they are reabsorbed by the capillaries, into the bloodstream.
Tubular secretion is the process in which renal tubule extracts chemicals from the capillary's blood and secretes them into the tubular fluid.
Some substances are retained in the bloodstream because they are bound to plasma proteins that cannot get through the membrane.
These substances have about the same concentration in the glomerular filtrate (fluid in the in the Bowman's capsule) as in the blood plasma.Nephrons are microscopic tube-like structures in the kidneys that filter the blood and cause wastes to be removed.They are the most basic structures of the kidney's anatomy. As the blood plasma flows through the nephrons, its composition changes.When tubular fluid leaves the renal tubule it goes to the collecting tubule (or collecting duct). The renal tubule of several nephrons drain into the collecting tubule.This results in a significant amount of water being drained into the collecting tubule.