lecture 4 continued Flashcards
what are the structures of the male system?
- many testes (ranging from 3 to 100’s depending on the tapeworm species)
- vasa efferentia
- vas deferens (often highly coiled)
- cirrus sac with cirrus
- common genital pore
sperm are mostly transferred between mature proglottids ___ ___ to each other
lying next
gravid proglottids ___ from parent organisms and ____ or ___ the host
detach
disintegrate
exit
eggs that pass from the host are …
embryonated
the eggs contain a …., called an ….
hexacanth larva
oncosphere
the oncosphere’s inner envelope is surrounded by another membrane structure called the ____
embryophore
the outer envelope lies between the ___ and the ___
embryophore
shell/capsule
how do cestodes take up nutrients given they lack a gut?
their external surface acts as a metabolically active layer taking up nutrients from the environment and also contains a later through which secretions and excretions must pass
the external surface of the cestode =
the tegument
what does the tegument have to do?
resist the attack of digestive enzymes and protect against the immune response of the host
what covers the entire surface of the tegument?
the glycocalyx - a lyer of carbohydrate containing macromolecules
what is the role of the glycocalyx?
- protecting the parasite from host digestive enzymes
- enhancing nutrient absorption
- maintaining the parasite’s surface membrane
what is the syntegument?
outer anucleate syncytical cytoplasmic layer containing mitochondria and secretory bodies
what is the cytotegument?
nucleated cell bodies lying beneath the tegumental muscles and connected to the syntegument
what is the role of the excretory system of all parasitic platyhelminthes?
allows the parasites to conserve water and eliminate salts and survive in the intestine or body cavities of their hosts- makes them act like osmoconformers
flame cells are …
ciliated cells located within the basal matrix of platyhelminthes. they are considered the basic units of excretory systems of invertebrates
the main excretory canals run the …
length of the strobila from the scolex to the posterior end
what are the two pairs of excretory canals?
the ventrolateral and the dorsolateral
the excretory ducts are lined with …
microvilli
whats the role of the microvilli lining the excretory ducts?
responsible for active transport of excretory waste and ionic regulation of excretory fluid
most cestodes are regarded as ____
osmoconformers
the main nerve center of a cestode is a ….
rectangular or circular nervous tissue in the scolex varying from a single ganglion to a combination of several ganglia and commissures
how is the cestode nervous system arranged?
like a ladder with paired ganglia near the anterior end, nerves running anteriorly toward sensory or holdfast organs and longitudinal nerve trunks extending posteriorly to near the end of the body
sensory structures are abundant and are arranged in …. patterns
species-specific
taenia saginata is known as the …
beef tapeworm
what is the definitive and intermediate host of the beef tapeworm?
- definitive host : always humans
- intermediate host: always cattle
in what organ of the human are adult beef tapeworms located?
the small intestine
what is the life cycle of taenia saginata?
1. Gravid proglottid ruptures on land during drying and releases eggs onto soil. 2. Grazing cow (intermediate host) must ingest the eggs. 3. Oncosphere hatches from egg in cow small intestine, penetrates intestine, and enters circulation. 4. Oncosphere reaches skeletal muscle and becomes a cysticercus. 5. Human eats raw or poorly cooked beef containing cysticerci. 6. Scolex evaginates, attaches to wall of ileum, and begins strobilization. 7. Adult reaches maturity and maximal length in 3 months
the released eggs of the Taenia spp are …..
morphologically indistinguishable
the taenia eggs are …
spherical with a thick radially striated brown embryophore
inside each taenia egg is an oncosphere that has ….
6 hooklets
cysticercus
the larvae of Taenia
what does Taenia saginata do in the tissue of the intermediate host?
the small scolex is invaginated into the cysticercus
what happens with Taenia saginata in the definitive host?
the scolex evaginates from the cysticercus
what is the scolex morphology of Taenia saginata?
scolex contains four suckers and no hooks
is taenia saginata hermaphroditic or dioecious?
hermaphroditic
taenia: gravid proglottids are identified by …
the presence of 15 or more side branches on either side of the uterus
taenia gravid proglottid is shed in …
feces
taenia solium is known as the …
pork tapeworm of humans
what is the definitive and intermediate host of taenia solium?
definitive: always humans
intermediate: pigs
why is taenia solium more dangerous than the beef tapeworm?
humans can also serve as accidental intermediate hosts
T. solium eggs are … to T. saginata eggs
identical - the small scolex is also invaginated into the cysticercus (in the tissue of the intermediate host) and evaginated from the scolex in the definitive host
what is the adult scolex morphology of T. solium?
scolex has 4 suckers and 2 circles of hooks
T. solium; gravid proglottids contain up to …
14 side branches on either side of the uterus - diagnostic stage in human feces
what is the life cycle of Taenia solium?
- Adult tapeworm is found in the human small intestine.
- Gravid proglottid is shed in feces.
- Gravid proglottid ruptures on land, releasing fertilized eggs onto soil.
- Pig (intermediate host) ingests embryonated eggs.
- In the pig, the oncosphere hatches from the egg and enters circulation.
- Oncosphere reaches skeletal muscle and becomes a cysticercus.
- Human eats raw or poorly cooked pork containing cysticerci (larvae).
- Cysticerci are released from the muscle in the stomach.
- Adult tapeworm develops in the small intestine (up to 2 ‐ 7 m in length and
produce approx. 1000 proglottids, each with ~ 50,000 eggs) and reside in the small intestine for years
T. solium cannot … if humans are the accidental intermediate host
develop into adult worms
what is the effect of humans being the accidental intermediate host?
causes cysticerosis - the resulting disease of being the accidental host
cysticerosis …
an infection of both humans and pigs with the larval stages of Taenia solium. this infection is caused by ingestion of eggs shed in feces of a human tapeworm carrier. pigs and humans become infected by ingesting eggs or gravid proglottids
what is autoinfection of Taenia solium?
human infected ingesting eggs produced by that tapeworm, either through fecal contamination or from proglottids carried into the stomach by reverse persistalsis (muscle contractions in the digestive tract)
what happens once eggs of T. solium are ingested?
oncospheres hatch in the intestine invade the intestinal wall, and migrate to striated muscles, as well as the brain, liver, and other tissues, where they develop into cysticerci
how is cysticercosis diagnosed?
by demonstrating the cysticercus in the tissue involved
how is cysticercosis treated?
- treated with anti-parasitic drugs in combination with anti-inflammatory drugs
- surgery, usually in the case of infected eyes or brain edemas
how is taeniasis treated?
praziquantel
what does praziquantel do?
increases the permeability of the worm’s membranes towards calcium ions
