Earthworm Excretory System Short Notes

Earthworm Excretory System Short Notes

In this article we will discuss about the earthworm excretory system

Earthworm Excretory System

  • The excretory system remove metabolic wastes and toxins from the body
  • Excretory organs of earthworm is nephridia
  • Nephridia occur in all segments of the body except for the first three
  • The earthworms are both ureotelic and ammonotelic and secrete both urea and ammonia as waste products


  • According to their position in the body, nephridia are of 3 types:- Septal Nephridia, Integumentary nephridia and Pharyngeal nephridia

1. Septal Nephridia

  • They are well developed and the largest nephridia
  • Found on inter segmental septa
  • Starting from 15 segment all posterior septa have nephridia
  • Each inter-segmental septum possess two rows of septal nephridia (80-100 on each septum)
  • Septal nephridium has 4 parts: Nephrostome (nephridiostome or ciliated funnel), neck, body of nephridium and terminal duct
  • Septal nephridia open into alimentary canal
  • Alimentary canal absorbs water from excretory materials

Function of septal nephridia

  • Septal nephridia discharge the waste products through canal and ducts into the lumen of the intestine. So they are enteronephric.

2. Integumentary nephridia

  • Present on the internal surface of body wall
  • Each segment has 200-250 nephridia
  • In clitellar segments has 2000-2500 nephredia. They are known as forest of nephridia
  • Each nephridium opens by a nephridiopore on the outer surface of the body wall directly.

Function of Integumentary nephridia

  • They discharge nitrogenous metabolic waste products directly outside from the body through nephridiopores. So they are called exonephric nephridia.

3. Pharyngeal nephridia

  • Present on 4,5,6 segment of alimentary canal
  • Similar to septal nehridia in structure but they lack nephrostome
  • Terminal ducts of each group unit to form a common duct
  • Common ducts open into pharynx in 4 segment

Function of Pharyngeal nephridia

  • They discharge the waste products directly into the buccal cavity and pharynx from where these are passed outside with undigested food through the anus. So they are called enteronephric nephridia.

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