Phylum Platyhelmi nthes

1. Phylum Platyhelminthes

2. I. Characteristics of Flatworms 1. Ectoderm – outer layer 2. Mesoderm – middle layer, containing organs 3. Endoderm – inner layer, lines digestive cavity. A. Three germ layers make them triploblastic B. BilateralSymmetry– with true cephalization C. Body flattened dorsoventrally, openings underneath D. Outer tegument for parasitic forms ONLY E. Primitive muscular system arising from Mesoderm F. Acoelomate – No true body cavity

3. H. Ladder Type Nervous System I. Simple sense organs – free living ones have Ocelli J. Simple excretory system – some with flame cells G. Incomplete digestive system – gastrovascular cavity K. NO respiratory, circulatory or skeletal systems. L. Most forms are monoecious (hermaphrodites)

4. II. Classification of Flatworms A. Class Turbellaria 1. Mostly free living 2. Most well known is the Planarian 3. Digestive system has a mouth, pharynx, and intestine which together forms a gastrovascular cavity. 4.Ocelliare common in Planaria. 5. Asexual Reproduction occurs by fission. 6. Sexual reproduction is by cross fertilization; Planaria are hermaphrodites, but cannot fertilize themselves. 7. They have remarkable regenerative capabilities.

5. Typical Planarian Ocelli

6. B. Class Trematoda – parasitic flukes 1. Outer body covered by protective tegument 2.Two hosts in some life cycles – the intermediate host where maturation and development of the larva takes place The other host is the definitive host, in which the sexual reproduction occurs.

7. Chlonorchis sinensis (Southeast Asia)

8. Chlonorchissinensis – human liver fluke a. eggs are deposited in water sources through human feces. b. eggs are ingested by the FIRSTintermediate host – the snail. c. The larvae hatch from the eggs and live in the snail until they develop into cercariae. d. The cercariae dig out of the snails and swim around. They burrow into a certain family of fishes, which are their SECONDintermediate host. e. Humans catch and eat the fish. f. The cercariae become adult worms in the definitive host and attack the liver and intestines, where they may live 15 – 30 years.

9. Schistosoma spp. Asia Africa Central and South America

10. Schistosoma – Human Blood Flukes (several species) a. Eggs are deposited into the water through human feces. b. The eggs hatch and larvae penetrate snails in the water. c. The larvae dig their way out of the snails. d. The free swimming larvae, known as cercariae, search for humans in the water – bathing, washing clothes, swimming, fishing, etc. e. They penetrate the humans and bore into circulatory and intestinal systems. f. They cause a disease known as schistosomiasis.

11. Beef Tapeworm Means “pregnant”

12. C. Class Cestoda – The Tapeworms 1. The head or holdfast of a tapeworm is called the scolex. 2. The individual reproductive segments are proglottids. 3. The entire chain of proglottids is called the strobila. 4. Taeniasaginata– The Beef Tapeworm a. intermediate host – cow b. definitive host – humans 5. Taeniasolium – The Pork Tapeworm a. intermediate host – pig b. definitive host - humans

14. Phylum NematodaThe Roundworms

15. I. Characteristics of Roundworms A. Pseudocoelomates - no true body cavity B. Hydrostatic Pressure for shape and structure. C. Most roundworms are less than 5 cm long, but some are over one meter in length. D. Outer protective cuticle made primarily of collagen. E. MOST nematodes are dioecious.

16. The flatworms showed us an acoelomatic arrangement. The Roundworms show us a pseudocoelomatic arrangement.

17. Flatworm arrangement

18. Roundworm Arrangement

19. Ascaris • 1. Most well known roundworms; easily studied • 2. Infection comes from eating • undercooked vegetables • 3. Infects intestines; eggs pass through fecal matter. II. Classification of Roundworms

20. B. Hookworms 1. Enter body through skin of feet 2. Eggs pass out through fecal matter 3. Heavy infestations cause anemia Mississippi leads the nation in Hookworm infestation! Don’t go barefoot!

21. C. Trichinella 1. Trichina worm found in pig muscle. 2. Contracted by eating undercooked pork. 3. Causes a disease called trichinosis. Typical Trichina larva inside pork – cook it well!

22. D. Filarial Worms – carried by insects (usually flies and mosquitoes!) • Heart Worms – Attack dogs, cats, even humans, get • into heart and clog it up, preventing free blood flow – often fatal for small animals

23. 2. Wuchereria bancroftii – filarial worm obtained from mosquito bites. They block the flow of the lymph nodes and lymphatic fluid. They cause a disease known as Elephantiasis.

24. Elephantiasis is marked by excessive growth and swelling, especially in the scrotum, legs, arms, and on occasion the vulva and breasts of human hosts.

25. Discussion Question for this Unit!!!*** Pinworms are usually ingested by children or adults after getting them on their hands from the soil. The eggs are often found under the fingernails of the person involved. The hands are then placed in the mouth, causing the eggs to hatch.

26. The larvae migrate to the intestines, where the male and female worms reproduce. The female crawls out of the host’s anus at night, laying her eggs around the anal sphincter with a glue-like substance that itches tremendously.

27. The host then scratches the anal area at night, causing the eggs to end up back under the fingernails. After placing their hands in their mouths, the process starts all over again! 30% of all toddlers in the USA get pinworms ! 16% of all adults in the USA get pinworms ! This is the most common helminth parasite in America!

28. That's all Folks! Test (B) Friday of this week and (A) Monday of next week