1. Phylum Annelida The Segmented Worms

2. Common name: Segmented worms
Characteristics:
Cephalization: Well-developed nervous system: nerve cord with ganglion in each segment and anterior brain
Bilaterally symmetrical
Organs within a true coelom (cavity within mesoderm)
Compartmentalization of organs / movement of parts of body
Closed circulatory system with five pairs of “aortic arches”

3. Sophisticated digestive system:
mouth – food enters
pharynx – passes through
esophagus – peristalsis
crop – storage
gizzard – grinding
intestine – more digestion
anus – waste exits

4. Intestine
Earthworm anatomy
Gizzard
Esophagus
Mouth
Crop
Pharynx

5. Appendages:
Setae: a stiff hair like or bristle like structure
Parapodium: Paired muscular bristle-bearing appendages used in locomotion, sensation, or respiration

6. Muscles
Circular muscles
Longitudinal muscles

7. remove nitrogenous wastes; wets skin No gills/lungs—use diffusion
Nephridium: A tubule open to the exterior that acts as an organ of excretion
remove nitrogenous wastes; wets skin
No gills/lungs—use diffusion
Most have red hemoglobin in blood
a red protein responsible for transporting oxygen in the blood 

8. Reproduction
Most are hermaphroditic
testes in 10th and 11th segments
ovaries in 13th segment
Clitellum stores eggs and produces “slime band” protective coat around eggs

9. Classes of Annelids
Oligochaeta: earthworms, night crawlers, (aquatic) tubifex worms
20-45 tons of soil/year/acre processed by worms on organic farms
each worm processes its own weight each day

10. Polychaeta: bristleworms, tube worms, featherdusters
marine worms with parapodia and (most) jaws

11. Hirudinea: terrestrial / aquatic leeches
some parasitic, some free-living
medicinal anticoagulant “hirudin”

12. Class Hirudinea
The medicinal leech is best known as the organism used for blood letting (people used to believe many health problems caused by "bad" blood). They are being used once again to remove blood from hematomas (areas of blood leakage) resulting from surgery (like re-attaching severed limbs, etc.).