Earthworm Vocabulary for
Dissection
*copy these words in your folder and define
for homework. These are the structures
that you will need to know the function and
location for during the dissection
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sperm ducts
prostomium
setae
dorsal blood vessel
ventral blood vessel
Closed circulatory system
mouth
anus
clitellum
DORSAL side
Cerebral Ganglia
Nephridia
Ventral nerve cord
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septa
seminal vesicles
Seminal receptacles
aortic arches
Crop
Mouth
Pharynx
Intestine
Gizzard
Anus
Esophagus
Pharyngeal Muscles
External anatomy of an earthworm
External cont…..
• External Structures
of the Worm
• 1 Mouth
2 Prostomium
3 Segment
4 Spermathecal
openings
5 Female (oviduct)
opening
6 Male (vas
deferens) opening
7 Sperm groove
8 Papilla
9 Clitellum (saddle)
10 Paired setae
(ventro-lateral)
11 Anus
12 Dorsal surface
13 Ventral surface
Dissection Guidelines:
• Internal Anatomy
• 1. Place the specimen in the dissecting pan
DORSAL side up
• 2. Locate the clitellum and insert the tip of the
scissors about 3 cm posterior.
• 3. Cut carefully all the way up to the head. Try to
keep the scissors pointed up, and only cut through
the skin.
• 4. Spread the skin of the worm out, use a teasing
needle to gently tear the septa (little thread like
structures that hold the skin to organs below it)
• 5. Place pins in the skin to hold it apart,
Internal view of earthworm
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Anus
Intestine
Cerebral ganglion
Prostomium
Mouth
Nerve collar
Segmental ganglion
Pharynx
Esophagus
Segmental nerve
Crop
Gizzard
Ventral nerve cord
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Anus
Dorso-subneural vessel
Intestine
Dorsal vessel
Hearts (aortic arches)
Mouth
Ventral vessel
Subneural vessel
Reproduction in earthworms