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2014-11-12 04:42:01
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  1. define parenchyma, acoelomate, tegument, syncytial, parasitic castration
    • parenchyma: connective tissue and muscle fibers that fill the space between body wall and internal organs
    • acoelomate: no true body cavity, it is filled with parenchyma
    • tegument: tough covering of trematode, synonymous with cuticle
    • syncytial: multinucleated without cell boundaries between nuclei (eg the tegument in trematodes)
    • parasitic castration: trematode larval parasites secrete chemicals to inhibit snail reproductive system
  2. Describe the anatomy of the tegument (platyhelminthes)
    • Distal cytoplasm: the outer portion of the tegument
    • covered by cell membrane and extends to basal lamina (separates proximal and distal cytoplasm)
    • spines may project out of membrane
    • glycocalyx is linked to plasma membrane, functions in attachment, protection, and uptake of vital molecules
    • Proximal cytoplasm: (AKA cyton region) the inner zone of tegument
    • connected to distal region by cytoplasmic bridges
    • circular, longitudinal, and diagonal muscles lie directly beneath the basal lamina
    • contains nuclei (note- syncytial), ER, golgi body, mitochondria, etc
    • responsible for the maintenance of the tegument
  3. Describe the functions of the tegument (platyhelminthes)
    • protection
    • nutrient absorption
    • synthesis/secretion of various nutrients
    • excretion
    • osmoregulation
    • sensory role
  4. Describe the general trematode digestive system
    • Incomplete
    • Mouth is anterior
    • Oral sucker: surrounds the mouth
    • ventral sucker: (AKA acetabulum) on ventral surface
    • alimentary tract is bifurcated to form 2 caeca
    • *NOTE- digestion is typically extracellular
  5. Describe the general trematode excretory system
    • protonephridial system (primitive kidney)
    • Flame cells w/ cilia -> terminal tubule -> collecting tubules -> excretory bladder -> excretory pore
    • *NOTE- major excretory product is ammonia
  6. Describe the general trematode reproductive system
    • Highly specialized
    • Very high capacity w/ complex life cycle
    • intermediate stages exhibit asexual reproduction
    • Monoecious: hermaphroditic
    • *NOTE- Schistosomes are dioecious
    • *NOTE- self-fertilization does not occur
    • Protandry: (AKA androgyny) male organs mature first, and produce sperm that is stored until needed
    • Protogyny: (AKA gyandry) ovary matures first (this is very rare)
  7. Describe the general male trematode reproductive system w/ pathway for sperm
    • Usually 2 testes
    • *NOTE- schisotomes have 4-9
    • vasa efferens: 
    • vas deferens: 
    • seminal vesicle: for storage
    • ejaculatory duct: 
    • cirrus: a penis
    • cirrus sac: encloses cirrus
    • testis -> vas efferens -> vas deferens -> cirrus sac -> cirrus
  8. Describe the general female trematode reproductive system w/egg
    • Singly ovary
    • Oviduct
    • seminal receptacle: sperm storage
    • 2 vitelline glands: yolk production / shell formation
    • ootype: chamber where eggs are formed
    • Mehlis' gland: lubricates uterus for egg passage
    • Laurer's canal: serve as vestigial vagina in some
    • uterus: allows shelled eggs to pass through genital pore
    • *NOTE- uterus is the largest organ in the body, and filled with 1000s of eggs
    • metraterm: muscular portion of uterus that propels eggs out
    • receives cirrus during copulation
  9. Describe general trematode eggs
    • Hard, smooth shell that contains vitelline membrane
    • contain developing miracidium
    • transparent
    • yellow/brownish
    • operculum: allows miracidium to hatch
    • *NOTE- schistosome egggs do not have operculum
    • Specific pH, light, and temperature conditions required for hatching
    • size, shoulders, spines, etc are important diagnostic tools
  10. Describe general trematode lifecycle
    • Eggs: released within lumen of host's organ and passed through feces or urine
    • Miracidium: ciliated stage released after egg reaches aquatic environment
    • finds and penetrates snail, shedding ciliated epidermis in the process
    • Sporocyst: development occurs around digestive gland, gonads, or mantle in snail
    • primary sporocysts may produce secondary sporocysts or rediae (asexually)
    • Rediae: first form to have functional gut/pharynx
    • give rise to tailed cercaria larva
    • cercaria: escape from gastropod
    • swim freely to second intermediate host OR encysts on vegetation
    • lose tail before becoming metacercaria
    • metacercaria: infective stage
    • migrates to definitive site after ingestion by definitive host
    • *NOTE- schistosomes lack metacercaria stage, as cercaria directly penetrate definite host
  11. Describe the general features of trematode Miracidium
    • small, elongated, ciliated
    • Can be mistaken for a protozoan
    • apical papilla: retractable, nonciliated apical tip with sensory organs
    • lateral glands and 1 apical gland aid in snail penetration
    • simple protonephridial system
    • internal germ cells eventually give rise to sporocysts
  12. Describe the general features of trematode Sporocyst
    • Grows near site of snail penetration
    • shape is highly variable
    • loss of all structures in miracidium, except protonephridia
    • No mouth/digestive system (nutrients absorbed)
    • Germ balls: develop into either sporocysts ("daughter generation") or differentiate into rediae
    • *NOTE- may modify snail behavior
  13. Describe the general features of trematode Redia
    • burst out of sporocyst
    • travel to snail digestive gland
    • elongated
    • blunt at posterior end
    • procursculi: (AKA ambulatory buds) stumpy appendages that aid in movement (crawling within host)
    • Functional digestive system w/ anterior mouth, muscular pharynx, and short unbranched cecum
    • Feed on host tissue as they move, causing damage
    • Germ balls differentiate into either secondary rediae (until they reach a certain population) or cercaria
    • Cercaria is released via the birth pore
  14. Describe the general features of trematode Cercaria
    • Usually specialized depending on spp / host
    • Most have tails to aid in swimming
    • Seek next host or preferred vegetation after exiting snail host
    • *NOTE - represents juvenile of adult trematode. Distribution of internal organs resembles adult.
    • Mouth, oral sucker, ventral sucker, pharynx, forked caeca, are all present (and should be IDd)
    • well developed excretory system
    • genital primordium: mass of germinal cells
    • that will form reproductive systems
    • several glands may be present that aid in various activities
  15. Describe the various glands that maybe present in a general trematode Cercaria
    • pentration gland: aids in host penetration
    • mucoid gland: aids in host penetration
    • escape gland: contents expelled during emergence from snail host
    • *NOTE - found in schisosomes
    • Preacetabular gland: contains enzymes important to penetration of host skin
    • postacetabular gland: produces mucus for adehsion/lubricaiton
    • cystogenous gland: form a cyst wall
    • *NOTE - in liver fluke cercaria (metacercaria)
  16. Describe the general features of trematode Metacercaria
    • *NOTE - this stage is absent in schistosomes
    • "Dormant" stage between cercaria and adult
    • encysted cercaria after penetrating secondary intermediate host OR finding suitable vegetation
    • further development occurs within cyst wall 
    • lives on stored nutrients
    • infective stage
    • Excysts (typically initiated by host intestinal conditions) and undergoes migration, growth, and gamete production as an adult after reaching definitive host.