platyhelminthes overview
Platyhelminthes are flatworms, which are bilaterally symmetrical. They are composed of three fundamental cell layers. They have a cephalized nervous system. There is no circulatory or respiratory system in platyhelminthes, and these normal functions take place by absorption through the body wall. Excretion by flatworms occurs through flame cells (specialized excretory cell) found in the protonephridia. Flatworms move because of longitude, circular, and oblique layers of muscle. Other flatworms move through slime trails. Most flatworms can reproduce either asexually or sexually, and sometimes both. Reproduction may be direct (eggs hatch) or indirect (ciliated larval form). Flatworms can be parasites and very dangerous to human beings.
TAPEWORMS
Tapeworms are flat segmented worms that are usually found in the intestines of animals. You can get tapeworms when you drink contaminated water are graze in pastures. The main cause of tapeworms however, is eating uncooked meat that is not prepared well. Tapeworms can have a minor effect on its host, but it could sometimes render in life threatening situations. They include a three cycle process, with the egg, larvae, and the adult stage. It is most common to get these tapeworms from undercooked cows or pigs. You can also inherit tapeworms from people, by not washing their hands and then preparing food. Some symptoms can include nausea, weakness, diarreaha, abdominal pain, and weight loss. Most of the time, there are no symptoms to having tapeworms. Over time, there can be damaging occurrences such as liver, eye, heart, and brain damage. To treat tapeworms, you should see a doctor, and take multiple blood tests to serif you have tapeworms. As flatworms (phlum Platyhelminthes), the soft flatworm body is ribbon-shaped, flattened flattened dorso-ventrally (from top to bottom), and bilaterally symmetric. They are acoelomates that are characterized by having three germ layers (ectoderm, mesoderm, and endoderm) and lacking respiratory and circulatory systems.
Cestoda is one of four classes of flatworms, the others being Trematoda (flukes), Monogenea, and Turbellaria. While turbellarians, such as planarias, tend to be free-living, the cestodes, trematodes, and monogeneans live as parasites in or on other animals.
Cestodes are covered with a cuticle (tough but flexible, non-mineral covering), and lack a true circulatory or respiratory system; they do have a bilateral nervous system.
citation: http://www.newworldencyclopedia.org/entry/tapeworm
Cestoda is one of four classes of flatworms, the others being Trematoda (flukes), Monogenea, and Turbellaria. While turbellarians, such as planarias, tend to be free-living, the cestodes, trematodes, and monogeneans live as parasites in or on other animals.
Cestodes are covered with a cuticle (tough but flexible, non-mineral covering), and lack a true circulatory or respiratory system; they do have a bilateral nervous system.
citation: http://www.newworldencyclopedia.org/entry/tapeworm
PLANARIA
Planaria lack specialized respiratory systems. They are larger than hydra, and have a thicker body of 3 layers instead of two compared to hydra. Planaria and other flatworms are flat to be thin enough for diffusion of gases to occur accross their skin. Planaria remain moist to facilitate gaseous diffusion and have a lot of surface area that helps with a lot of diffusion. They usually have a very close association with the circulatory system in order to get the gases to all cells of the body. Planaria undergo respiration through skin, gills and internal air structures.
TURBELLARIA
The Turbellaria are one of the traditional sub-divisions of the phylum Platyhelminthes(flatworms), and include all the sub-groups that are not exclusively parasitic. There are about 4,500 species, which range from 1 mm (0.039 in) to 600 mm (24 in) in length. All the larger forms are flat with ribbon-like or leaf-like shapes, since their lack of respiratory and circulatory systems means that they have to rely on diffusion for internal transport of metabolites.
Citation: http://en.wikipedia.org/wiki/Flatworm
Turbellarians do not have a respiratory or circulatory system, they exchange gases by diffusion through all their cells. They have a muscular mouth, called a pharynx, as well as a saclike digestive cavity.
citation : http://www.encyclopedia.com/topic/Turbellarians.aspx
Citation: http://en.wikipedia.org/wiki/Flatworm
Turbellarians do not have a respiratory or circulatory system, they exchange gases by diffusion through all their cells. They have a muscular mouth, called a pharynx, as well as a saclike digestive cavity.
citation : http://www.encyclopedia.com/topic/Turbellarians.aspx