A nephridiopore is a pore at the end of the nephridium, an excretory organ found in invertebrates, such as flatworms and annelids. [1] Nephridiopores open on the ventral surface of the body wall and allow metabolic wastes filtered by the nephridium to exit the body.[2]

Nephridia are homologous to nephrons or uriniferous tubules found in the kidneys of vertebrates. They occur in two forms: metanephridia, which begin with a nephrostome, and protonephridia, which begin with a flame cell. Fluids collected by the nephrostome or flame cell pass through a ciliated tubule,[3] where essential substances are reabsorbed through active mechanisms and waste products are secreted back into the lumen of the tube.[4] The resulting excretory fluid or urine is then passed out through the nephridiopore.[3]

References

  1. ^ "nephridium | anatomy | Britannica". www.britannica.com. Retrieved 2022-03-08.
  2. ^ "Lab 7: Annelids and Smaller Ecdysozoans". www.uwlax.edu. Archived 8 February 2023 at the Wayback Machine. Retrieved 23 December 2025.
  3. ^ Molnar, Charles & Gair, Jane (2015-05-14). "22.3. Excretion Systems"
  4. ^ "41.3B: Flame Cells of Planaria and Nephridia of Worms". Biology LibreTexts. 2018-07-17. Retrieved 2022-03-08.