Key functions of excretory systems include:
- Filtration.
Water and solutes are forced across the membranes of capillaries
to produce a filtrate.
- Reabsorption.
Valuable solutes such as glucose and amino acids are reclaimed from the filtrate
by active transport.
- Secretion.
Toxins and excess ions are extracted from body fluids to the filtrate by active transport.
- Excretion.
The filtrate leaves the system.