The document summarizes the anatomy and physiology of earthworms. It describes their external anatomy, as well as major internal systems including nervous, digestive, circulatory, excretory, respiratory, reproductive, muscular and skeletal. Key points are that earthworms have a segmented tube-shaped body, a closed circulatory system with blood containing hemoglobin, a hydrostatic skeleton made of fluid-filled chambers, and specialized sensory receptors allowing them to detect touch, vibrations and light. The document also provides reasons for studying earthworm anatomy, such as for education, disease research, and environmental applications like vermicomposting.

1. Anatomy and Physiology of Earthworm
by
Balogun Wasiu Gbolahan

2. Anatomy and Physiology of Earthworm
 General overview
 External anatomy
 Nervous system
 Digestive system
 Circulatory system
 Excretory system
 Respiratory system
 Reproductive system
 Muscular system
 Skeletal system
 Special senses
 Why Study Earthworm?

3. General overview
•Phylum: Annelida
•Shape: tube-shaped
•Body structure:
metamerically segmented
•Habitat: inside the
earthworm or moist
places
•Feed: live or dead
organic matter

4. External Anatomy

5. Nervous system

6. Nervous system
• The Peripheral nervous system
a. Eight to ten nerves arise from the cerebral ganglia to
supply the prostomium, buccal chamber and pharynx.
b. Three pairs of nerves arise from the sub-pharyangeal
ganglia to supply the 2nd, 3rd and 4th segment.
c. Three pairs of nerves extend from each segmental ganglia
to supply various structures of the segment.
• The sympathetic nervous system consists of nerve plexuses
in the epidermis and alimentary canal.

7. Digestive system

8. Circulatory system
The earthworm has a
closed circulatory system.
An earthworm circulates
blood exclusively through
vessels.
Presence of haemoglobin

9. Excretory system
• The excretory system contains a pair of
nephridia in every segment, except for
the first three and the last ones.
• The three types of nephridia are:
1. The integumentary nephridia lie
attached to the inner side of the body
wall in all segments except the first two.
2. The septal nephridia are attached to
both sides of the septa behind the 15th
segment.
3. The pharyngeal nephridia are attached
to fourth, fifth and sixth segments.

10. Respiratory system
• There is no formalized respiratory system in
earthworms; exchange of oxygen and carbon
dioxide takes place through the moist cuticle.
• Respiration normally occurs in air but
earthworms can exist in water for long periods of
time (e.g. for six months) if the water is
oxygenated.

11. Reproductive system

12. Copulation and Fertilisation

13. Muscular system
Useful
•Movement
•Digestion of
food

14. Skeletal system
• They lack either an internal skeleton or
exoskeleton, but maintain their structure with
fluid-filled coelom chambers that function as a
hydrostatic skeleton.

15. Special senses
• The Epidermal Receptors: These are found all over the
epidermis but are more numerous on the lateral and
ventral surface of the body. Earthworms are very sensitive
to touch and to vibrations transmitted through solid
objects.
• Buccal Receptors: They are found in large numbers in the
epithelium of buccal cavity. These are olfactoreceptors
and gustatoreceptors. Thus the earthworms can recognize
different types of leaves that can be used as food.
• Photoreceptors: They are found in the inner parts of the
epidermis. The photoreceptors are restricted to the dorsal
surface and are more numerous on the prostomium and
first segment. The photoreceptors enable the worm to

16. Photoreceptor cells in Prostomium

17. Why Study Earthworm?
• Understanding of animals for our own education
and management purposes.
• Choose appropriate animals models to study
disease.
• Add to human cultural base.
• Studying soil pollution.
• Vermicomposting.
• Bait for fishing.

18. Links for further reading
• http://www.sas.upenn.edu/~rlenet/Earthworms.
html
• http://www.northallegheny.org/Page/19944
• http://ibis.geog.ubc.ca/biodiversity/efauna/Earth
wormsIntroduction.html
• http://cronodon.com/BioTech/Earthworm_NS.ht
ml
• http://passscience.blogspot.my/2010/09/reprod
uctive-system-of-earthworm.html

19. Thank you for
your time