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Flatworms Phylum: Platyhelminthes 3 Germ layers Bilateral symmetry Acoelomates: No body cavity Results in thin, flat bodies Low surface area:volume ratio Gastrovascular Cavity Nutrients/Waste enter/exit same location Divided into three classes Turbellaria Majority are marine species Often called planarians Aquatic scavengers Very simple digestive system Free living, so they need to breakdown their own nutrients Few live in freshwater Must excrete excess H2O Uses excretory tubule system shown in 36-2 Trematoda Called Flukes Mainly parasitic Attach to the host by a sucker Draws body fluid of host into the fluke Tegument Outer portion of the fluke Protects against the host’s immune/defense stystem Fluke Reproduction (36-4) Complex life cycle Different host at different points in life cycle Primary Host Host that the adult lives in Consumes nutrients Reproduces Intermediate Host Larval stage of development Larva get nourishment Used to get back to the primary Host Cestoda Tapeworms Intestinal parasites Tegument similar to flukes Scolex used to attach to the host Body segments called proglottids Grows by adding segments Some may have over 2000 (over 30 ft) Completely lack digestive organs Absorb directly from host Cestoda Reproduction Complex life cycle similar to flukes Proglottid contains eggs Proglottid breaks off Carries eggs away in feces Vegitation contaminated by feces Eggs fertilized by other segment on same worm, or different worm in same host Consumed by herbivore Eggs develop into larva in intermediate host Get to muscle and form cyst Primary host consumes animal muscle Phylum: Nematoda Roundworms Long,slender, tapered at anterior and posterior ends Pseudocoelomates Complete digestive tract 2 openings Covered by a cuticle:used for protection Free living and parasitic Ascaris Intestinal parasite Enter body through contanimated food Pig, human, horse May block intestinal tract Eggs carried out in feces Egg Larva in intestine Larva Bloodstream Bloodstream Lungs/throat Lungs/Throat Outside body(cough), intestine(swallowed) Hookworm Intestinal parasite Remove blood Can cause anemia Eggs released through feces Eggs develop into larvae in soil Larvae burrow into foot Get into bloodstream Follow similar path of ascaris Trichinella Embed in intestinal walls Larvae enter bloodstream, go to muscle, form cyst Consumed in undercooked meat Mainly pork ALWAYS WELL DONE!!! Causes trichinosis Muscle pain/stiffness If in heart = death Pinworm Most common in US (16% adult, 30%children) Do not cause major illness Intestinal Eggs deposited outside anus Eggs picked up, moved to other locations Ingested eggs end up back in intestines Filarial Worms Tropical Parasites Some live in lymphatic system Transferred by mosquitoes Can completely block lymphatic vessels Mosquito is intermediate host Where the larvae develops Transfer to new host Causes elephantiasis Also what causes heartworm in dogs