Exam 3 parasit

Exam 3 parasit - July 11-18 PLATYHELMINTHES II CESTODES...

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Unformatted text preview: July 11-18 PLATYHELMINTHES II CESTODES “Tapeworms” • Dorsoventrally flattened • No digestive system • No coelom—body cavity • No circulatory system • No respiratory system • Well developed muscular system • Complex nervous system • Hermaphroditic • At least 2 different hosts in life cycle • Host niche: intestinal tract in definitive host • All are parasitic • No pathology to gut mucosa in definitive host Proglottid —segment that has sets of reproductive organs of both sexes ?Genitalium —term used for each set of sex organs Strobila —long chain of proglottids Strobilization —production of proglottids Growth of strobila from anterior to posterior • Immature mature gravid • Immature mature gravid senile (uterus shed all eggs before proglottid is shed) Basic Cestode Morphology: • Scolex • Neck • Proglottids o Immature o Mature o Gravid o Senile (only in pseudophyllidians) Scolex —anterior end of worm, “head” • “Holdfast” organs o Grooves/slits o Suckers o Hooks • Rostellum Sucker-like organs on scolex: 1. Acetabulum (plural—acetabula) • muscular and Round or cup-shaped • 4 on scolex 2. Bothria “slit-like” • Shallow pits or long grooves • Usual pattern: 2 3. Rostellum • Domed shaped area on end of scolex • Protrudes from scolex • Hooks ”armed” • No hooks ”unarmed” Neck : • Between scolex and strobila • Contains stem cells • These give rise to new proglottids o Once a cestode reaches its adult number of proglottids, no longer grows in size o Number of new proglottids = number of shed proglottids Tegument: (old term—“cuticle”) • All nutrition absorbed through tegument o No GI tract • Covered in microvilli (“microtriches” (plural—microthrix)) o Increase surface area to absorb nutrients from host GI tract • Functions in absorption (all nutrition absorbed through tegument), excretion (waste products of metabolism; osmoregulation) o Things are moving across tegument—nutrients, waste, and water Glycocalyx • Outermost covering of tapeworm o Outside of tegument • Composed of carbohydrate molecules • Functions: o Protection Protects against pancreatic digestive enzymes o ?Maintenance of tegument integrity o ?Nutrition o ?Absorbs bile salts Calcareous Corpuscles • Structures in cestode tissues • Inorganic component in organic matrix o Ca2+, Mg2+, carbonates, CaPO4 • Function?? Unknown: o Protein, lipid, glycogen, RNA & DNA, mucopolysaccharides, alkaline phosphate Muscular system: • Proglottid- 2 layers of muscle o Contractile fibers: actin and myosin myofibrils—same as us • Shed proglottids “crawl” around o Not senile proglottids Nervous system: • Nerve ganglion in scolex o No central nervous system • Numerous sensory endings on surface: o Sensory: find best location in gut to obtain nutrients Tactoreception (to find best location in gut to obtain nutrients) Chemoreception (to find best location in gut to obtain nutrients)...
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Exam 3 parasit - July 11-18 PLATYHELMINTHES II CESTODES...

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