Kingdom Animalia:Nematoda: life cycle

Ascaris lumbricoides● Ascaris lumbricoides or roundworms

infect humans and pigs. The species

can pass between humans and pigs in

a manner similar to that of tapeworms

but with the added complication that

in humans the worm also passes

through the lungs.

Reproduction and life cycle● Adult females in the intestine produce

eggs that pass out in the feces. A typical female can produce up to

200,000 eggs every day.

● The eggs can be ingested with

contaminated food or water and form

the first stage larvae. These burrow

through the intestinal wall into the

bloodstream and pass through

the liver to the lungs. In

the blood vessels of the

lungs, they develop

into the next stage and

move into the alveoli.● The larvae in the lungs

are coughed up and

pass down into the

stomach and then to

the small intestine. It

is in the small

intestine that they

complete development to

become sexually mature

adults.

alveolusfecesintestinelarva

Key words

Roundworm life cycle

Ascaris Iumbricoides adults in human intestine

human gutAn infective larva develops within an egg.

The egg passes out in the feces.

larva

eggcapsule

humanlungs

human liver

Ascaris Iumbricoidesadults live in thehuman intestine.

The larva passesthrough the gutwall into thebloodstream.

Having passed throughthe liver and lungs, alarva is coughed upand swallowed.

An egg is eatenby a human; thelarva hatches inthe intestine.

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