ProstomiumA fleshy lobe overhanging the mouth. It seals the mouth at rest and senses the surroundings.
SegmentsThe ring-shaped sections the body is divided into, outside and in.
ClitellumA belt-shaped glandular swelling on adult worms. It makes the egg capsules. Part of the reproductive system.
PharynxA muscular pump that sucks in food.
Aortic archesFive pairs of vessels round the gut that act as hearts. They pump blood to the ventral vessel.
CropA thin-walled swelling where food passes on its way to the gizzard.
GizzardA muscular organ that grinds food, helped by swallowed mineral particles.
IntestineWhere food is digested, running from the gizzard to the anus.
The outside: 6 3
MouthThe opening in the first segment where food goes in.
SetaeBristle-like hairs on most segments. They anchor parts of the body as the worm moves.
AnusThe opening at the rear end where waste leaves the gut.
Inside: 8 3
Cerebral gangliaIt is the earthworm's brain. A pair of pear-shaped ganglia above the front of the gut.
EsophagusThe tube carrying food back from the pharynx toward the crop.
Dorsal blood vesselThe blood vessel along the top of the gut. Its contractions move blood forward.
How this list was compiled: Read 2026-09-26. Wikipedia, Earthworm, https://en.wikipedia.org/wiki/Earthworm : a segmented body with setae on most segments, used to anchor body parts as it moves; the first segment with the mouth and the prostomium overhanging it, sealing it and sensing the surroundings; the clitellum as a belt-shaped glandular swelling toward the front, part of the reproductive system, producing egg capsules; the gut running mouth to anus: buccal cavity, pharynx (a suction pump), esophagus, crop, gizzard (grinding with ingested mineral particles) and intestine; the dorsal blood vessel moving blood forward; aortic arches in segments seven to eleven acting as hearts, pumping to the ventral vessel; the brain as a pair of pear-shaped cerebral ganglia above the gut. Licence: own work
The drawing: Drawn for this site by script, 2026-09-26. Own work, nothing traced. Licence: own work
How it works
An earthworm diagram labeled in two views: the outside with its clitellum and setae, and the worm opened along the back as in a lab dissection, from the pharynx to the intestine. Start with the 8 main parts.
Read the full guide
The outside
The body is a row of segments. At the front, the prostomium overhangs the mouth; the clitellum is the thick band near the front that makes egg capsules. Setae on the segments anchor the body as it moves, and the anus is at the rear.
The gut and hearts
Food is sucked in by the pharynx, passes down the esophagus to the crop and is ground in the muscular gizzard before the intestine digests it. Five pairs of aortic arches round the esophagus act as hearts, and the dorsal blood vessel runs along the top.
Crop stores, gizzard grinds: the thin-walled swelling comes first, the muscular one second.
Questions and answers
How many hearts does an earthworm have?
It has five pairs of aortic arches, often called hearts, around the esophagus. They pump blood to the ventral vessel.
What is the clitellum?
A thick, belt-shaped band near the front of an adult earthworm. It is part of the reproductive system and makes the capsules the eggs are laid in.
What does the gizzard do in an earthworm?
It grinds food with strong muscular contractions, helped by mineral particles swallowed with the food.