Earthworm Dissection

External Anatomy

examine your earthworm and also determine thedorsal and also ventral sides. Situate the clitellum i m sorry is ~ above the anterior end of the worm. Locate the mouth of the worm top top the much anterior end of the worm The openings toward the anterior that theworm room the sperm ductsThe openings near the clitellum are the genital setae.

Locate the dark line the runs under thedorsal next of the worm, this is the dorsal blood vessel. The ventral blood vessel deserve to be checked out on the underside the the worm,though the is typically not as dark.

Locate the worm"s anus on the much posterior finish of the worm

note the ede of the earthworm close to its anterior side, this is the clitellum.

label the earthworm pictured:

A = _________________________________ B = _________________________________ C = _________________________________ D = _________________________________

Internal Anatomy

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1. Location the specimen in the dissecting pan DORSAL side up. 2. Situate the clitellum and insert the guideline ofthe scissors about 3 cm posterior (behind the clitellum). 3. Cut closely all the method up to the head.Try to store the scissors spicy up, and only cut through the skin. 4. Spread the skin that the worm out, usage a needle to tenderness tear the septa (little thread prefer structures thathold the skin to organs below it) 5. Ar pins in the skin to organize it apart, edge the pins out so that they room not in your way.

Reproductive System

The very first structures you most likely see room the seminal vesicles. They are cream colored and located toward the anteriorof the worm. These are supplied for creating sperm. Usage tweezers come removethese white structures from over the top of the digestive mechanism that liesunderneath it.

Circulatory device

The dorsal blood vessel (X) appears as a darkbrownish-red courage running follow me the intestine. The heart or aorticarches (Y) have the right to be uncovered over the stomach (just posterior to the pharynx). Carefully tease away the tissues to reveal the arcs of the heart, the runacross the worm.How plenty of aortic arches can girlfriend count? ______

The ventral blood vessel (Z) is the contrary thedorsal blood vessel, and also cannot it is in seen currently because the digestivesystem consist of it.

brand the diagram (use the letters next to the bold words above)


Does the earthworm have actually a closeup of the door or open up circulatorysystem? ________________

Digestive device

The digestive system starts at the mouth. Youwill map the organs all the way to the anus and identify each on the worm.

Find the mouth opening, the an initial part ~ themouth is the pharynx, friend will see stringy points attached to one of two people sideof the pharynx (pharyngeal muscles) . The esophagus leader from the pharynxbut you probably won’t be able to see it, due to the fact that it lies underneath the heart .You will uncover a two structures close to the clitellum. Very first in the orderis the crop , followed by the gizzard . The gizzard leads to the intestine which is as lengthy as the worm and also ends at the anus .

*Use her scissors to cut open the crop and also thegizzard. Which one has the harder exterior? ___________

Place in the correct order (number)

____ Anus ____ chop ____ Mouth ____ Gizzard ____ stomach ____ Intestine ____ Pharynx

Nervous System

Locate the brain at the far anterior an ar of the worm. That is really tiny and also whitish colored. If friend can"t find it, it is probably due to the fact that it was damaged when you cut the worm. You have the right to locate the ventral nerve cord by remove the intestines and also searching for a white string-like structure that operation the length of the worm and attaches to the brain. Eliminate the intestines and locate the ventral nerve cord.

Lab Analysis (Answer True of False; most of the answers have the right to be uncovered in this worksheet)

1. ____ The mind attaches come the ventral nerve cord.2. ____ The dorsal side of the worm is lighter than the ventral side..3. ____ The clitellum is situated toward the anterior end of the worm. 4. ____ The esophagus lies in ~ the pharynx5. ____ Earthworms room hermaphrodites. 6. ____ The ventral nerve cord and also the ventral blood vessel room connected. 7. ____ The pale string-like structure running the length of the ventral side of the worm is the blood vessel.8. ____ an earthworm has fourteen aortic arches. 9. ____ The dorsal blood vessel can be checked out from the worm"s exterior.10. ____ Serminal vesicles are part of the worm"s cradle system.


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Label these structures on the image: pharynx, esophagus, crop, gizzard, aortic arches, brain, dorsal blood vessel, seminal vesicles, clitellum



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