Mr and Mrs Smith's Life Science

WORM NOTES        Last Updated 10/19/2005

FLAT WORMS: Platyhelminthes

3 cell layers
hooks and suckers
no digestive system; absorb food

Turbellaria: The Turbellaria are free-living, freshwater flatworms commonly called planaria. They range is size from microscopic to several inches in length.

Trematoda: The Trematoda consistute the flukes. The flukes are parasitic flatworms. Flukes characteristically possess suckers, usually two or more, used to attach themselves to their host. Much of a fluke's body cavity is occupied by reproductive organs. Flukes may be either external or internal feeders, and some fluke groups have extremely complicated life histories.

Cestoda: The Cestoda are made up of the tapeworms. Tapeworms are internal parasites of vertebrates. The body is composed of a small head and neck, followed by a large number of segments (proglottids). Each segment is a reproductive sack and as it ripens it breaks off and pass to the outside of the host in its feces. Can grow to be several feet long.

     Life Cycle of the Tapeworm
     
1. A cow eats grass contaminated with tapeworm eggs.
      2. The eggs pass to the cow's intestine.
      3. Eggs hatch and develop into immature worms.
      4. The worms are carried by the cow's blood to its muscles.
      5. Cow is sent to slaughter house.
      6. Meat sent to stores.
      7. Meat is bought amd taken home.
      8. If meat is poorly cooked the worms do not die.
      9. We eat the meat.
      10. The immature worms develop into mature tapeworms and they live in your intestine.
      11. Mature worms produce eggs, which are passed out of the humans in solid waste.

Tapeworms are parasites which have no digestive system of their own, so they attach to the intestines and eat the food which we digest. The longest tapeworm ever passed by a person was 39 meters. Tapeworms attach to the wall of the intestines using their "scolex." The scolex is the head of the tapeworm which is composed of hooks for attaching, and suckers for drinking food. Tapeworms are composed of segments called "proglottides." Each proglottid grows in size and ruptures releasing eggs, each of which becomes a new tapeworm. Tapeworms are hermaphroditic (one body having both sexual parts) and they fertilize their own eggs. Humans most often get tapeworms from undercooked pork, beef or fish. Tapeworm eggs can withstand boiling water, so it is important to cook these meats well enough to destroy the eggs. Children sometimes get tapeworms by playing with the feces in the litter box of a cat, getting the eggs on their hands, and placing their hands or fingers in their mouth.

The primary symptom of tapeworms is weight loss. Tapeworm eggs have been capsuled and sold as a diet pill. When the desired amount of weight was lost, one took another pill which killed the tapeworms. Effective, but not a good idea medically.


ROUNDWORMS: Nematodes

Live on land and in water
Complete digestive system: two openings: mouth and anus
No circulatory system
No respiratory system
3000 roundworms can be in one gram of raw or undercooked pork

Hookworms: burrow through skin of feet, to intestines, where they live on blood   camera.GIF (174 bytes)PH 10-17  p.272
       Pinworms
       Ascaris
       Trichinella: lives in the muscles of pigs  camera.GIF (174 bytes)PH 10-16   p.271

Life Cycle of Trichinella
  
1. Lives in muscles of pigs.
   2. Person eats undercooked pork.
   3. Live and reproduce in your intestine.
   4. Females release hundreds of immature roundworms.
   5. Immature roundworms are carried in the bloodstream.
   6. Immature roundworms burrow into surrounding tissue and organs.
   7. Cause terriffic pain.
   8. Once in tissue and organs, worms become inactive.

The phylum Nematoda are the roundworms. Roundworms are cylindrical in shape and vary in length from being microscopic to being 20 inches long. Unlike flatworms, roundworms have a complete gut. This means that they have a gut which begins with a mouth and ends with an anus. Therefore, they are usually able to digest food. However, roundworms have no blood or heart. Nutrients are distributed by a non-blood fluid which is not pumped. Roundworms can be parasites. The roundworm trichinella, causes the disease called trichinosis. People get trichinosis from eating undercooked pork. Trichinella get into muscles and leave calcium deposits which effect muscle contraction. Trichinosis can affect the heart. Another roundworm, ascaris, parasitizes human lungs. Hookworms and pinworms are also roundworms which parasitize humans.

SEGMENTED WORMS: Annelids
  
9000 species
   Divided into segments
   Slimy outer layer
   Closed circulatory system: 10 ringed blood vessels called hearts
   Complete digestive system
   Feed on dead plant and animal matter
   No respiratory system
   Simple nervous system

Earthworms
Leeches
Sandworms  camera.GIF (174 bytes)PH 10-18  p.272