Phylum Platyhelminthes PDF

Phylum Platyhelminthes Kingdom Animalia Subkingdom Parazoa Subkingdom Metazoa Diploblastica Triploblastica Cnidaria Rest of all animals  General Characteristics They exhibit bilateral symmetry: anterio...

Phylum Platyhelminthes Kingdom Animalia Subkingdom Parazoa Subkingdom Metazoa Diploblastica Triploblastica Cnidaria Rest of all animals  General Characteristics They exhibit bilateral symmetry: anterior and posterior ends are different; so are the dorsal (top) and ventral (bottom) surfaces The platyhelminths also exhibit some degree of cephalization Commonly referred to as the 'flatworms' because their bodies are dorsoventrally flattened. They are acoelomates This phylum (and all remaining phyla) possess 3 germ layers (=triploblastic) The mesoderm (third germ layer) gives rise to muscles, various organ systems, and the parenchyma, a form of solid tissue containing cells and fibers  Outer Body Covering The body of some platyhelminthes (e.g., turbellarians) is covered by a ciliated epidermis Epidermal cells contain rod-shaped structures called rhabdites that when released into the surrounding water, expand and form a protective mucous coat around the animal The outer body covering of other platyhelminthes (e.g., parasitic forms) is a non-ciliated tegument Organ Systems of the Platyhelminthes Digestive System Some of the flatworms possess a digestive system, with a mouth, pharynx, and a branching intestine from which the nutrients are absorbed The intestine, with only one opening, is a blind system Organ Systems of the Platyhelminthes cont. Excretory System (osmoregulation) A network of water collecting tubules adjacent to flame cells or a protonephridia When cilia beat they move water into the tubules and out the body through pores called nephridiopores Organ Systems of the Platyhelminthes con’t Muscular System Below the epidermis are layers of circular and longitudinal muscle fibers; used in locomotion Nervous System Includes: anterior cerebral ganglia, longitudinal nerve cords, and some lateral nerves Most free living planarians and parasitic larval forms possess a variety of sensory organs (e.g., eye spots, statocysts, rheoreceptors) Organ Systems of the Platyhelminthes cont. Reproductive System Most are capable of some form of asexual reproduction (e.g., many turbellarians reproduce by fission) Most flatworms are hermaphroditic; however, they often pair with other individuals to exchange gametes Platyhelminthes Taxonomy Phylum: Platyhelminthes ↓↓↓ Class: Turbellaria Trematoda Cestoda ↓↓↓ Liver fluke Blood Fluke Intestinal fluke  Liver fluke Kingdom: Animalia Subkingdom: Metazoa Phylum: Platyhelminthes Class: Trematoda Genus: Fasciola Species: hepatica Ex: Fasciola hepatica Fasciola hepatica Fasciola gigantica Body wall structure Life cycle of Fasciola hepatica  Blood fluke Kingdom: Animalia Subkingdom: Metazoa Phylum: Platyhelminthes Class: Trematoda Genus: Schistosoma Ex1: Schistosoma haematobium Ex2: Schistosoma mansoni Life cycle of Schistosoma sp.  Impacts of schistosomiasis Liver granuloma Ascites