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