Download Ventral

Earthworm Anatomy
Earthworm Classification
• Kingdom: Animalia
Phylum: Annelida
Class: Oligochaeta
Order: Abranchiata
Family: Lumbricidae
Genus: Lumbricus
Species: terrestris
Vocaulary
•Dorsal-top side
•Ventral-bottom side
vocabulary
• Anterior- head end
• Posterior- tail end
• If you look at my body under a magnifying glass, you will
see a lot of little rings across my entire body . . . These
rings are called segments.
• When I am all grown up, I will have 100-175 segments.
On the first segment is my mouth and on the last
segment is my anus—sort of like the beginning and the
end.
• At the very tip of my head (that's the anterior,
remember), you will see a flap of skin that hangs
over my mouth. It is called the prostomium. It
keeps stuff I don't like from getting into my
mouth.
• Right under the prostomium is my mouth. I
have a pretty big mouth for a worm. It's big
enough to grab a leaf and drag it around.
How does an earthworm move?
• Muscles expand and contract to help the earthworm move
• If you look really, really closely at each segment, you will see
something that looks like a bunch of small hairs or bristles. These
bristles are called setae (pronounced see-tee) and they help me
move. I have four pairs of these bristly hairs on each ring or
segment.
Clitellum
• Forms a cocoon into which eggs are
deposited during reproduction
Digestive System
• One way digestive system with a mouth
and an anus
• Has tubes that remove waste in each
segment
• Droppings (called castings) help to
fertilize the soil
Mouth
Pharynx - aids in swallowing food
Esophagus- carries food to the
crop
Crop – temporarily stores food; the walls of the
crop are thin and soft
•
Since I have no teeth, I cannot really chew my food like you do. I do have
something inside of me close to my mouth called a gizzard. You might have
heard this word before because birds, including chickens and turkeys, have
a gizzard almost like mine. As I eat my food some grains of sand and soil
get into my gizzard. These grains of sand and soil push against each other,
mix with moisture and grind the food into tiny pieces (kind of like my own
personal food processor).
•
When the food leaves my gizzard, it goes into my intestine. The food is
dissolved there and absorbed into my blood. Then it is carried to all parts of
my body to keep me strong, healthy and slimy.
Gizzard – grinds food with soil; gizzard is
tough, thick, and muscular
Intestines – where nutrients are absorbed
Anus- where waste passes out of
the Earthworm’s body
Reproduction
• When mating, another worm and I join together
with heads pointing in opposite directions.
Sperm is passed from one worm to the other
and stored in sacs. Then a cocoon forms on
each of us on our clitellum. As we back out of
the narrowing cocoons, eggs and sperm are
deposited in the cocoon.
• When I am a few weeks old you will notice a
light-colored band forming near my front end.
This is my clitellum. My clitellum will someday
help to form cocoons. New baby worms will
hatch from the cocoons and I will have a family.
Clitellum
Seminal Vesicles – male reproductive
organs
Ovaries - female reproductive organs
Circulatory System
• Closed circulatory system
• Blood moves within a connected network
of blood vessels, as opposed to an open
circulatory system where blood sloshes
around inside the body (like in insects)
• Closed moves blood more quickly
• Pumps blood through 5 aortic arches to
the lower part.
• I have five hearts! All of these hearts pump
blood through my blood vessels just like
your one heart.
Dorsal Blood Vessel
Aortic Arches (hearts)
Ventral blood vessel
Nervous System
• Knot of nerves in head called
ganglia make up the brain
• Parallel nerve cords that runs
the length of the body
Ventral Nerve Cord
Respiratory System
Worms do not have lungs but I breathe through my
skin. I take in oxygen through my skin and it goes right
into my bloodstream. My skin must stay wet in order for
the oxygen to pass through it, but if I am in too much
water I will drown. Just keep me damp, moist and slimy.