- The anterior end is the head, which is slightly pointed and has a mouth.
- The posterior end is the tail, which is more rounded.
- The dorsal side is the top surface of the worm.
- The ventral side is the bottom surface of the worm.
- The lateral sides are the left and right sides of the worm.
- The worm is bilaterally symmetrical.
- The coelom is the body cavity between the body wall and the digestive tract.
- The septa are the thin, membranous walls that divide the coelom into segments.
- The circulatory system is closed; blood flows through vessels.
- The ventral blood vessel is the main vessel running along the underside of the worm.
- The dorsal blood vessel is the main vessel running along the top of the worm.
- The hearts (aortic arches) pump blood from the dorsal to the ventral vessel.
- There are 5 pairs of hearts (10 total) located in segments 7–11.
- The digestive system runs from the mouth to the anus.
- The crop stores food; the gizzard grinds it.
- The intestine absorbs nutrients.
- The nephridia are excretory organs that remove waste.
- The clitellum is a thickened glandular section involved in reproduction.
- Sperm is produced in the testes and stored in seminal vesicles.
- Eggs are produced in the ovaries.
- During mating, worms exchange sperm.
- The clitellum secretes a cocoon that holds fertilized eggs.
- The cocoon is deposited in soil, where embryos develop.
Parent Tip: Review the logic above to help your child master the concept of earthworm anatomy worksheets.
