Excretory structures and functions in Annelida?

Annelida, which includes earthworms and leeches, have excretory structures called nephridia. Nephridia are tubular structures that are responsible for excretion and osmoregulation in these organisms.

The main function of nephridia is to remove metabolic waste products, such as ammonia, from the body. They also help in maintaining the water and ion balance in the organism.

In earthworms, there are two types of nephridia: septal nephridia and pharyngeal nephridia. Septal nephridia are located in each segment of the earthworm's body and are responsible for excreting waste products. Pharyngeal nephridia, on the other hand, are located near the pharynx and help in osmoregulation by removing excess water from the body.

In leeches, there are three types of nephridia: cephalic nephridia, gastric nephridia, and caudal nephridia. Cephalic nephridia are located in the head region and help in excreting waste products. Gastric nephridia are found in the digestive system and assist in removing excess water and ions. Caudal nephridia are located in the posterior region and are responsible for excreting waste products.

Overall, the excretory structures in Annelida play a crucial role in maintaining the internal environment of the organism by removing waste products and regulating water and ion balance.