The document provides notes on the external and internal anatomy of earthworms. Externally, earthworms have setae (tiny hairs) in rings along their segmented body and a clitellum (knob) near the center that secretes fluid to enclose fertilized eggs. Internally, the main organs are located between the mouth and clitellum, including the ganglia which acts as the worm's brain, and aortic arches that circulate blood and nutrients. The digestive system includes a pharynx, esophagus, crop, gizzard, and intestine for breaking down and transporting food. Reproductive organs include seminal receptacles that receive sperm for fertilization and seminal vesicles that

1. BIOLOGY
Unit 7:
Earthworm Notes

2. (1) External Parts
• Setae:
– Rings / Segments
– Contain tiny hairs to help with movement + sex.
• Clitellum:
– Knob near center-length of worm.
– Secretes fluid to enclose fertilized eggs.
• Mouth vs. Anus:
– Mouth = Closer to Clitellum
– Anus = Further away from Clitellum

3. (2) Internal Parts
*MOST INTERNAL PARTS ARE BETWEEN
THE MOUTH + CLITELLUM.*
• Ganglia:
– Fleshy bit right behind the mouth.
– “Brain” of worm.
• Aortic Arches:
– Tiny black, finger-nail looking bits.
– Circulate blood / nutrients.

4. (3) Digestive Organs
• Pharynx:
– Round Bump behind mouth + ganglia.
– Starts to break down food.
• Esophagus:
– Wrinkly tube leaving the mouth + pharynx.
– Carries food to next organs.
• Crop:
– Round lump after esophagus.
– Stores food before digestion.
• Gizzard:
– Round lump after crop.
– Contains stones to break apart food.

5. Digestive Organs (Cont’d)
• Intestine:
– Long skinny tube leaving gizzard.
– Goes rest of length of worm.

6. (4) Reproductive Organs
• Seminal Receptacles:
– Fleshy colored lumps/bits, behind the hearts.
– Receive sperm for egg fertilization.
• Seminal Vesicles:
– Small fleshy lumps/bits, behind hearts.
– Release + store sperm.

10. ---Dissection Notes---
1. Lie worm on its belly (rounded/darker side
pointed up).
2. Identify clitellum.
3. Carefully cut from MOUTH  CLITELLUM
4. Carefully peel back skin.
5. Identify organs.

11. External Dorsal:
Clitellum
Mouth
Dorsal Blood Vessel
(Dark Line) Anus

12. External Ventral:
Mouth
Clitellum Genital
Setae
Sperm
Ducts Female
Genital
Pores

13. Internal:
Intestine Gizzard
Crop
Seminal
Vessicles
Seminal
Recepticles
Aortic
Arches
Esophagus
Pharynx
Ganglia
(Brain)

14. Internal w/o Digestive…
Nerve
Cord
(Like our
Spinal
Cord)
Seminal
Receptacles