Excretory system in earthworm - SS2 Biology Lesson Note

EARTHWORM

The excretory system in an earthworm consists of specialized structures called nephridia. Earthworms have multiple pairs of nephridia distributed along the length of their body segments. These nephridia function as excretory and osmoregulatory organs.

Here is an overview of the excretory system in earthworms:

1.       Nephridia:

·         Nephridia are tubular structures responsible for excretion and the removal of metabolic wastes from the body fluids of earthworms.

·         Each body segment of an earthworm typically contains a pair of nephridia, except for the first three segments, which lack nephridia.

·         The nephridia are connected to coiled tubules that extend into the body cavity and open to the exterior through tiny pores called nephridiopores.

2.       Nephridial Function:

·         The main function of the nephridia is to filter and remove nitrogenous waste products, such as ammonia, from the body fluids.

·         The nephridia also help maintain the osmotic balance and regulate the levels of water and ions in the earthworm's body.

·         They play a role in excreting excess water and maintaining proper osmotic concentration within the body.

3.       Process of Excretion:

·         The excretory process in earthworms involves filtration, reabsorption, and secretion.

·         Body fluids containing waste products are filtered by the ciliated cells lining the nephridial tubules.

·         Useful substances and some water are reabsorbed back into the body through the walls of the tubules.

·         Waste products and excess water are further concentrated and transported through the tubules to the bladder-like structure called the urinary bladder or urinary vesicle.

·         The waste products are then eliminated from the earthworm's body through the nephridiopores.

The excretory system in earthworms plays a vital role in maintaining the internal environment of the organism by removing metabolic waste products and regulating water and ion balance. It ensures the efficient excretion of waste materials and helps the earthworm maintain homeostasis.