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Helminths (Worms) Multicellular (metazoa) bilaterally symmetrical organisms having 3 germ layers ecto-, meso- and endo-derms (triploblastic metazoa).

Helminths (Worms)
Multicellular (metazoa) bilaterally symmetrical organisms having 3 germ layers
ecto-, meso- and endo-derms (triploblastic metazoa).
The word, helminths from Greek means "Worm"
The helminths are generally macroscopic, and they are the cause of
high morbidity and mortality of people worldwide. They cause different
diseases in humans, but few helminthic infections cause life- threatening
diseases.
adult worms vary tremendously in size from barely visible to 10 meters in
length.
The clinical sign and symptoms of helminthicinfections depend on the
location of the organisms and may be caused by adults, larva, or eggs. a-Trematodes
Liver flukes(fasciola hepatica).
Intestinal flukes(fasciolopsis buski).
Lung pulmonary flukes paragonimus westerman).
Blood flukes(schistesoma spp.).
B-Cestoda.
2-Phylum,Nemathelminthes(round worm)
Aphasmid nematodes, no chemoreceptor.
Phasmid nematodes, with chemo receptors. Phylum Platyhelminthes(Cestodes)
A- Pseudophylidia -Diphyllobothrium latum is a flat tapeworm (Fish
tape worm or board tape worm), is the longest parasite that
infects humans: adult worms can achieve a length of more
than 10 m (33 feet) in the small intestine
1-Definitive Host: Fish-eating carnivores, including dogs, bears,
humans.
2-1-First Intermediate Host: Crustaceans, including copepods.
2-2-Second Intermediate Host: Fish.
-Fish eats copepod with procercoid larvae.

• Definitive Host : eats fish with plerocercoid(sparganum). Taeniasagi nata(Beef tape worm)
  Scolex of T.sagi nataand solium
  Geographical Distribution: World wide distribution Habitat
  Adult: In small intestine of man(4-8m).
  Larvae: In muscular tissues of cattle.
  Eggs: In faeces of man or in gravid segments.
  Life cycle
  Requires two hosts to complete its life cycle. Human as a definitiv
  e host and cattle as intermediate host.
  The larval cyst of T. sagi nata—the (C ysticercus b ovis)—is a pea-
  sized, fluid-filled cyst, which develops in the muscles of the
  intermediate host. Within the cyst is a single inverted scolex,
  formed from a germinate portion of the inner cyst wall. Taeniasolium,
  (Pork Tape worm)
  Geographical Distribution:-Widely distributed
  Habitat:
  Adult: In the small intestine of man(2-4m).
  Larva: In muscular tissues of pig
  Egg: In the faeces of man and in gravid segment.
  Life Cycle:
  The life cycle of T.solium is similar to that of T. sagi nata ex
  cept pigserving as an intermediate host for the development of la
  rvae known as(C ysticercuscellulosae).
  (Tegument cells cover with absorptive hair for absorption of
  nutrient )
  Pathogenesis: Causes taeniasis Major symptoms are loss of appetite, weight
  loss, hunger, acute intestinal obstruction, eosinophilia, and
  discomfort by the crawling of segments through the anus.
  The hooked scolex of T. soliummay cause greater intestinal
  disturbance, pain, and inflammatory response than that caused
  by T.sagi nata.
  However, T. soliumlarval infection (cysticercosis) is a
  potentially dangerous systemic infection, the degree of damage
  depending on the site and number of cysticercus (cysticercus
  cellulosae) that develop. Infection most commonly occurs in the
  central nervous system (CNS)(neurocysticercosis). It is also
  frequently found in muscles and subcutaneous tissues. The globe
  of the eye is also a common site.