Earthworm Excretory
system
http://image.tutorvista.com/content/excretion-and-osmoregulation/earthworm-cross-section.jpeg
New Vocabulary
• Coelom – Body cavity, space
• Nephridia – unit of the excretory system in
earthworms
• ‘stome’ – mouth like opening
• Earthworm belongs to
Phylum Annelida (higher
invertebrates)
• Excretory systems consists
of nephridia which are
small, coiled tubes along the
body.
3 types of nephridia depending
on location
• Septal (behind the 15th segment)
• Integumentary( along the inner
side of body)
• Pharyngeal(4th, 5th, 6th segments
only)
• A typical nephridium consists of a ciliated
funnel or nephridiostome which opens into
the coelomic cavity.
http://shs.westport.k12.ct.us/mjvl/biology/dissect/earthworm_images/earthworm_nephridia.gif
• This is followed by a short and narrow
tube called the neck which is bent on itself
and opens into the main body of the
nephridium.
• The cells lining the
nephridiostome and the
nephridial tube bear cilia in
some lengths. The lashing
movements of the cilia help in
the flow of the excretory
matter.
Process of Excretion
• Since the nephridia are richly
supplied with capillaries,
n_ _ _ _ _ _ _ _ _s wastes are
removed from the blood.
• The rhythmic beating of the cilia
of the nephridiostomes drives a
steady stream of coelomic fluid
containing metabolic waste
materials, such as u_ _a,
a_ _ _ _ _ a and remains of dead
cells, into and through the
nephridial tube.
• The excretory wastes are then
finally discharged into the gut.
Only waste matter is excreted
from the capillaries with which
they are richly supplied. Thus
water is conserved by these
nephridia.
Reference:
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