Learn the extretion of Earthworm .
The body of earthworm is divided into a series of similar segments. These segments are internally divided by septa. Excretory organs of the earthworm are called nephridia which are attached to the septa. Nephridia are coiled tubes. Nephridia are absent in the first three segments. There are two types of nephridia – (1) Septa (2) Pharyngeal (3) Integumentary. Nephridia show two types of excretion. (1) Enteronephric excretion (2) exonephric excretion. In enteronephric excretion, the excretory products are poured into the alimentary canal through nephridia.
In exonephric excretion the excretory products are thrown out through the skin. At the anterior end of the nephridium there is a funnel like structure called nephrostome and its end has an opening called nephridiopore. Fluid from body cavity carrying waste, enters the nephrostome. The cilia present in the tubule helps the fluid to move through the nephridium. During this process glucose and useful substances are reabsorbed by cells lining the tubules and passed into the blood. The remaining waste fluid is thrown out through nephridiopore.