Other Aschelminths Flashcards
Organisms considered “Eutelyosts” share what trait?
Have a fixed number of somatic cells their whole life cycle, which only grow bigger throughout life.
The Aschelminths are generally considered to have what basic traits?
Live in water, usually “worm shaped”, no blood-vascular system or true coelom, digestive tract is a complete tube, and they usually have some form of ashesive organs.
Nematode bodies are completely encased in a non-living _____. Describe this.
Cuticle. Composed of many sub-layers of polymers of chitin. It is bendable and resilient but it cannot stretch outwards
Where do nematodes most often live?
Must live in water. Typically live in soil (along plant roots), water, or host animals. Found basically all over the entire world.
What does the drug Pyrantel pamoate do to susceptible nematodes?
Induces a state of tetanus (constant muscle contraction)
Briefly describe the general physical characteristics of nematodes
Round in cross section, often round and thin, usually only a few mms long but can be as much as a meter long. Have a thick cuticle that must be molted/shed periodicially. Have a tubular gut with anterior mouth surrounded by lips and sensory structures. Buccal cavity is sometimes armed with teeth or rasping structures.
TRUE OR FALSE: All nematodes hatch out of eggs outside of the mother
FALSE, some hatch inside the mother and are birthed live
How many juvenile stages are there in nematodes? What happens during each transition? Which stage is usually infective?
4 stages, with a cuticle molt at each stage. Usually the third is infective.
What is the purpose of the lateral, dorsal, and ventral ducts in nematodes?
Lateral ducts likely used for excretory functions.
Dorsal and ventral hold the dorsal and ventral nerve cords.
Describe the structure of the gut in most nematodes
Usually have a muscular pharynx which can bypass the high pressure of the body cavity by rhythmically contracting and opening and closing a flap below the pharynx (connecting pharynx and esophagus)
What is unique about the body fluid in nematodes?
Under extremely high pressure, actually compresses the gut when it is not full
What kind of muscles exist in nematodes?
Lateral (only longitudinal, no circular) muscles all along the body with long extensions of the muscles reaching out to the dorsal and ventral nerve cords
Why don’t nematodes have circular muscles?
They can’t contract the body because of the cuticle anyway, so they would not be useful
How is nematode sperm unique among metazoans?
Sperm have no flagella, and are in fact amoeboid
Briefly describe nematode gonads
Very simple with the gametogenic organism at one end and the gonopore at the other end. Ex. ovary at one end which becomes uterus which becomes the vagina.
Describe the external physical differences between male and female nematode.
Males typically have a hooked tail for grabbing female during reproduction.
Hookworm males have a ______ used to wrap around the female during copulation. Describe this.
Some other nematodes have something similar called a _____
Bursa - a large flat disk used to attach to female
Pseudobursa - like little legs for wrapping around the female
_____ can be inserted by nematodes into the vagina to open the vagina. Why is this necessary?
Spicules. This is needed because the body is under such high hydraulic pressure that the vagina is naturally shut
The Order Trichurida is also referred to as ____. Why is this?
whipworms. They look like whips, with an enlarged posterior end and a very thin anterior half
A whipworm infection is referred to as _____ and is a result of infection with ____
Trichuriasis. Trichurus trichiura
Describe the lifecycle of T. trichiura
Direct life cycle.
Egg comes out in feces, starts at 1 cell stage, moves into 1 cell stage, and develops through more advances cleavage into embryonated egg. Fecal-oral contamination results in ingestion of embryonated egg, which becomes a larva, penetrates host mucosa, and becomes an adult.
____ is localized inflammation and increased blood flow that causes a red colour
Erythema
What kind of symptoms does T. trichiura infection in the large intestine produce?
Usually nothing, but when someone has more than 100 worms, diarrhea, inflammation, bloody diarrhea, abdominal pain, rectal prolapse can occur.
How is T. trichiura distributed across the world
Tropical areas (eggs cannot survive above frost line), areas with poor sanitation practices or pooping in places other than bathrooms. Also present in southern US
How is T. trichiura diagnosed?
By finding whipworm eggs in feces (microscope). Sometimes concentration is necessary. Also possible to examine rectal mucosa by proctoscopy
What is the drug of choice for nematodes? What does it do?
Mebendazole. Causes worm death be selectively and irreversibly blocking glucose/nutrient uptake in adult intestine where helminths dwell.
What is the absolute best way to mitigate T. trichiura risk?
EDUCATION
What is the basic egg morphology of T. trichiura?
idk
How was Trichinella spiralis discovered?
Mortician found that cutting through people’s muscles was dulling his scalpel. IT was found that within the muscle cells of of some people there were tubercles made of collagen containing small worms. A network of tiny “venules” called a “Rete” was found to form around the worm, creating a tiny little incubator (just based on hormone signals). Sometimes the tubercles become calcified, which was what caused the dulling of the scalpel.
What is the transmission cycle of Trichonella spiralis?
IT develops completely in one host, but can be transferred by carnivory. Only animals that eat flesh can be infected.
