Circulatory system of an Earthworm

Earthworm Dissection-PAP Bio- 3/12/14- Xiong, Lizi

Lumbricus terrestris

Earthworms (sometimes called night crawlers) are a class of Oligochaeta. They belong to the Kingdom Animalia under the phylum Annelida. Depending on the system, they belong to the order of Opisthopora or Haplotaxida. The adult is characterized by "rings" around the body, the lack of a vertebrae, and a tube-shaped body. The folk names of an earthworm include "dew-worm", "rainworm", "night crawler", and "angleworm". "Angleworm" is most likely due to its use as fishing bait.

While earthworms are known for the ability to live after being cut into two, this is in fact, a myth. Earthworms have their entire digestive system running down the length of its body. It also has a simple, closed blood circulatory system. Earthworms have also been placed int eh suborder Lumbricina of the order Haplotaxida due to Theoretical cladistic studies. This may soon change.

Today's Objectives

Students will be learning about the external and internal structure of the earthworm. Students will focus on the organs, structures, and functions of the circulatory system. Students will also understand the ecological role of the earthworm.

Evolution of Annelids

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Earthworm Dissection

Circulatory system at a glance

The earthworm has a closed circulatory system where the blood is recirculated throughout the body.Oxygen is absorbed directly from the soil. Earthworms do not have lungs. Oxygen is entered through the dorsal blood vessel where it travels to the five aortic arches (hearts). The esophagus pumps the blood to the lower, ventral blood vessel. Blood is then sent to all segments and organs in need of oxygen. A small blood vessel sends blood back from the ventral vessel to the dorsal vessel in each segment.


Five aortic arches: pump blood

Dorsal vessels: take blood back to front

Ventral vessels: take blood front to back

Capillaries: carries blood to proper areas and helps absorb nutrients


The circulatory system is one of the seven systems of the earthworm: respiratory, muscular, digestive, excretory, nervous, reproductive.

Human Impact

Earthworms are loved by human gardeners as they create rich soil. Some humans try to keep earthworms safe and healthy for a better garden. Unfortunately, many humans try to use chemicals to kill pests that feed on crops. The chemicals also kill the earthworms.