Phylum annelida- excretion in annelida


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my ppt describes mainly the excretory system in annelids.......

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Phylum annelida- excretion in annelida

  1. 1. PHYLUM ANNELIDA by Priyanka Mangotra
  2. 2. ABOUT ANNELIDS • Defining charac.- one or more pairs of chitinous setae • Complete digestive tract • Closed circulatory system • Ventral nervous system • Segmented worms For eg: earthworms, leeches, tubifex worms
  4. 4. • Fundamental unit of excretory sys.NEPHRIDIA • Two pairs of nephridia in each body segment • Excrete water, mineral, salts and nitrogenous wastes in the form of urea
  5. 5. SEGMENTAL ORGANS • There are certain tubes called SEGMENTAL organs, as they are repeated in successive segments. • Severe to convey the excretory/reproductive products from coelom to the exterior • They are divided into: NEPHRIDIA(derived from ectoderm) & COELOMODUCTS(from mesoderm) • Goodrich after careful embryological study revealed that neph and coel were 2 morphologically diffrnt structures.
  6. 6. COELOMODUCTS • Segmentally arranged wide tubes of mesodermal origin • Opens on one hand to the exterior by a genital pore & on the other into the coelom by relatively large ciliated funnel, the COELOMOSTOME.
  7. 7.  I. II. III. FUNCTIONS OF COELOMODUCTS Primarily as gonoducts Secondarily as excretory organs As reproductive funnels & ducts in oligochaeta (earthworms) IV. As the uriniferous tubules forming the vertebrate kidney.
  8. 8. NEPHRIDIA • Segmentally arranged coiled tubules of ectodermal origin • Ciliated internally & develped as inpushings/invaginations from the ectoderm so that they project into the coelom. • Communicate on one hand with exterior through laterally placed small apertures called NEPHRIDIOPORES.
  9. 9. Nephridium
  10. 10. FUNCTIONS OF NEPHRIDIA 1. Primarily function as excretory. 2. Secondarily to convey the genital products to the exterior 3. May as well play some role in maintaining salt & water balance.
  11. 11. Nephridiapore Nephrostome
  12. 12. TYPES OF NEPHRIDIA • • • • Protonephridia(closed) Metanephridia(opened) Mega and micronephridia Exo and enteronephridia
  13. 13. Protonephridia • Closed type- seems to be more primitive type • Terminates in the coelom as a blind tube • Closed pre-septal end provided with peculiar specialized excretory TUBE CELLS / SOLENOCYTES. • Found in Vanadis, Phyllodoce, Tomopteris, etc.
  14. 14. METANEPHRIDIA • Opened type- far advanced • Absence of solenocytes, its inner pre-septal end opens into coelom by a ciliated funnel called NEPHROSTOME. • Thus open at both ends • Exc. Wastes diffuse from coelomic fluid/ blood into the lumen of the nephridial tubule & discharged to the outside through NEPHRIDIOPORE. • Found in- polychaeta(Neanthes), oligochatea (Lumbricus) & leeches
  15. 15. Metanephridia
  16. 16. MICRO & MEGA NEPHRIDIA Micro/ mero nephridia • Smaller but numerous in each seg. • Networks of fine tubes lying on the body wall & septa in each segment. • Found in- Pheretima. Mega/ holo nephridia • Larger but generally one pair per seg. • Usually extend over two segments & their nephrostomes open into the segs. Next in front. • Found in- Polychaeta & Hirudinea.
  17. 17. • Its said a pair of originally meganephridia has broken up to form a large no. of micronephridia. • In Megascolex, micro & mega neph. Exist even in same segment of worm. • Serpula & other tubicolous worms- division of labour exists Anterior region- mega neph.- excretory in function. Posterior region- micro neph.- serve as gonoduct.
  18. 18. EXO & ENTERO NEPHRIDIA Exo/ecto nephridia • Directly open to the exterior • Nephridiopores present • Such asMeganephridia of Nereis, Hirudinaria & Lumbricus Integumentary micronephridia of Pheretima. Entero nephridia • Open into the excretory canals / alimentary canals • Nephridiopores absent • Such asSeptal & pharyngeal nephridia of Pheretima.
  19. 19. NEPHROMIXIA • Compound segmental organs. • Coelomoducts become fused partially / wholly with nephridia to form nephromixia. • Consist of ectoderm & mesoderm- serve for both excretion & exit of gametes.
  20. 20. DEGREE OF COMBINATION 1. Protonephromixium• coelomoduct +protonephridium • Convey both reproductive & excretory products to the ext. • Found in- Phyllodoce
  21. 21. 2. Metanephromixium• Coelomoduct + metanephridium • Found in- Hesione. 3. Mixonephridium• Coelomoduct + nephridium • Funnel is formed by coelomoduct • Duct formed by nephridium • Occur in Arenicola.
  22. 22. 4. Ciliated organs• Coelomoducts reduced to ciliated organs • In Nereis, they are attached to the dorsolateral longitudinal muscles & known to open externally.
  23. 23. EXCRETORY SYS IN PHERETIMA acc to the position of neph In the body is distinguished into: • Nephrostome • Body of nephridium • Terminal duct • Nephridial duct SEPTAL PHARYNGEAL INTEGUMENTARORY • 10 times the usual no. • Called FORESTS of nephridia.
  24. 24. PHYSIOLOGY • Gland cells extract- excess water + urea + ammonia + creatinine –from blood. • Septal nephridia eliminate solid part. From coelomic fluid through nephrostomes.  Integumentary neph(exonephric)- discharge wastes directly to the exterior.  Septal & pharyngeal neph- forms enteronephric nephridial sys- discharge into the lumen of the gut
  25. 25. Special enteronephric nephridial arrangement also serves for conservation of water / osmoregulation. SELECTIVE RESORPTION- excretory fluid discharged into pharynx moisten the food, as the faeces become compacted water is reabsorbed by intestine to be re-used by the body. Reabsorption of salts also occurs during fluid through the nephridia, this process is called S.R.
  26. 26. Another means of excr.: CHLORAGOGEN CELLS • Yellow cells called chloragogen cells. • Found in intestine & the dorsal blood vessel in large no. • Derived from the peritoneum/coelomic epithelium of the alimentary canal. • Take up nitrogenous waste products from the blood capillaries of the gut & deposited as yellow granules(guanin) in their cytoplasm.
  27. 27. • These cells are also concerned with -deamination of proteins -formation of ammonia -synthesis of urea Therefore, they are as the vital intermediary in metabolism of earthworms as the liver in vertebrates.
  28. 28. THANK YOU