Nematode Anatomy and Reproductive Structures

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Questions and Answers

What is the primary function of the stylet in certain organisms?

To penetrate plant cell walls (correct)

To facilitate respiration

To store nutrients

To aid in locomotion

Which of the following characteristics is unique to the rhabditiform esophagus?

Presence of three esophageal glands

Club-shaped anterior portion

Thickly lined with cuticle

Pear-shaped posterior bulb (correct)

What type of reproductive system does a male possess?

Two uteri and two ovaries

Single testis and vas deferens (correct)

Multiple seminal vesicles

Gubernaculum and two spicules

In the context of reproduction, what does oviviparous mean?

Development occurs inside the mother with live birth Signup and view all the answers

What is the primary mode of transmission (MOT) for species with active, free-living larvae?

Ingestion through food and water Signup and view all the answers

What does the esophagus variation indicate in these organisms?

The classification of species Signup and view all the answers

What is the function of genital papillae in males?

Supporting the caudal alae or copulatory bursae Signup and view all the answers

In species that require an intermediate host, how do larvae enter the definitive host?

By ingestion of the intermediate host Signup and view all the answers

What defines the relationship between a parasite and its host?

Parasitism Signup and view all the answers

Which of the following is a mechanism of host tissue destruction by parasites?

Excessive proliferation of host epithelium Signup and view all the answers

What is the typical shape of many parasites as described?

Cylindrical and elongate Signup and view all the answers

Which structure on a nematode is associated with chemoreception?

Phasmids Signup and view all the answers

What physiological effect can parasites cause related to food utilization?

Decreased appetite Signup and view all the answers

What feature indicates that a parasite may be dioecious?

Existence of distinct male and female forms Signup and view all the answers

What does a thicker cuticle in parasites typically indicate?

Resistance to host immune response Signup and view all the answers

Where are amphids located on a nematode?

On each side of the head Signup and view all the answers

What is the primary method of transmission for Ascaris suum?

Ingestion of eggs with food or water Signup and view all the answers

Which of the following describes the eggs of Ascaris suum?

Oval-shaped with thick shells and projections Signup and view all the answers

What is a characteristic of male Toxocara canis?

Tail with a terminal narrow appendage Signup and view all the answers

Which of the following organisms primarily infects equines?

Parascaris equorum Signup and view all the answers

What kind of life cycle does Toxascaris leonina have?

Direct life cycle with limited larval migration Signup and view all the answers

What is a possible clinical sign of heavy infection by Parascaris equorum?

Flatulence and pot-bellied appearance Signup and view all the answers

What aspect of Ascaris suum's life cycle allows for the eggs to appear in feces?

Eggs are laid in the digestive tract after migration Signup and view all the answers

Which of the following is a treatment option for Toxocara canis?

Piperazine Signup and view all the answers

What structural feature is unique to nematodes discussed?

Absence of a buccal capsule Signup and view all the answers

Which type of pathology occurs due to Ascaris suum infection?

Development of fibrotic lesions in the liver Signup and view all the answers

In the life cycle of Toxocara canis, which type of transmission can occur?

Transuterine and lactogenic transmission Signup and view all the answers

What is a significant effect of heavy infections of Ascaris suum?

Malnutrition and intestinal blockage Signup and view all the answers

What is the size range for female Parascaris equorum?

25-50 cm Signup and view all the answers

What is the primary route for Toxocara canis migration to the lungs?

Tracheal route Signup and view all the answers

Which of the following is NOT associated with the clinical signs of Toxocara canis infection?

Coughing and sneezing Signup and view all the answers

What is unique about the mode of transmission of Strongyloides stercoralis?

Direct skin penetration by larvae Signup and view all the answers

What life stage of Toxocara cati is typically passed to puppies through colostrum?

L3 Signup and view all the answers

What clinical signs are indicative of a severe Strongyloides stercoralis infection in dogs?

Erosion of the intestinal mucosa and microbleeding Signup and view all the answers

What is the mode of transmission for Anisakis spp. to humans?

Ingestion of raw or semi-raw fish Signup and view all the answers

Which characteristic helps distinguish Oxyuris equi from other nematodes?

Presence of anal pruritus Signup and view all the answers

Which treatment is commonly recommended for Strongyloides stercoralis in dogs?

Fenbendazole Signup and view all the answers

What is the primary site of infection for Stephanurus dentatus?

Kidney and perirenal tissues Signup and view all the answers

How are Oxyuris equi eggs primarily transmitted?

Ingestion of infective eggs on bedding Signup and view all the answers

What is a significant clinical sign that indicates the presence of Enterobius vermicularis?

Anal pruritus Signup and view all the answers

Which of the following is NOT a clinical sign associated with Stephanurus dentatus infection?

Coughing Signup and view all the answers

What anatomical feature is characteristic of Anisakis spp.?

Three inconspicuous lips Signup and view all the answers

What type of eggs do Strongyloides stercoralis females produce?

Thin-shelled transparent eggs Signup and view all the answers

What is a common treatment for defeating Stephanurus dentatus?

Levamisole Signup and view all the answers

What type of migration is primarily associated with L2 larvae of Toxocara canis?

Somatic migration Signup and view all the answers

In which host does Oxyuris equi primarily reside?

Equines Signup and view all the answers

How do gravid female parasites of the pinworm migrate?

Toward the perianal region Signup and view all the answers

What form of infection does the Strongyloides stercoralis life cycle exhibit?

Homogonic cycle Signup and view all the answers

Which of the following is a notable symptom of infection with Strongyloides stercoralis in dogs?

Moderate anemia Signup and view all the answers

What is the significant clinical feature associated with the necrosis of intestinal mucosa due to Strongyloides stercoralis?

Bloody diarrhea Signup and view all the answers

Which anatomical feature is characteristic of Stephanurus dentatus?

Spicules for reproduction Signup and view all the answers

What type of eggs does Stephanurus dentatus produce?

Thin-shelled ellipsoidal eggs Signup and view all the answers

Study Notes

Chemosensory Organs and Esophagus Structure

Amphids and phasmids are specialized chemosensory organs in nematodes.
The stylet is a hollow, protrusible structure for puncturing plant cell walls.
The esophagus aids in species classification, displaying variations:
- Triradiate lumen with a thick cuticle.
- Contains three esophageal glands.
- Features an esophageal bulb located posteriorly.

Types of Esophagus

Rhabditiform esophagus:
- Club-shaped anterior and narrow neck connecting to a pear-shaped posterior bulb.
Filariform esophagus:
- Club-shaped, lacking a posterior bulb.

Reproductive Structures

Male nematodes have a unique reproductive system with:
- Single testis and vas deferens, sometimes a seminal vesicle and muscular ejaculatory duct.
- One or two spicules within sheaths, along with gubernaculum and telamon.
Female nematodes possess:
- Posterior vulva, two uteri, and two ovaries.
- Can be oviparous, ovoviviparous, or viviparous.

Larval Life Cycle

Active third stage larvae are non-parasitic and enter hosts through the mouth.
Passive infective eggs contain the second or third stage larvae, which require an intermediate host for development.
Without an intermediate host:
- Eggs hatch externally, and larvae are free-living.
- Modes of transmission (MOT): food, water, or skin penetration.
With an intermediate host:
- Eggs can hatch or the worms can be viviparous, with larvae developing inside.

Key Nematode Genera

Ascaris, Parascaris, Toxascaris, and Toxocara are medically significant genera.
Nematodes often have specific body features:
- Three large lips and no buccal capsule.
- Female tails are blunt, while males have coiled tails with spicules.

Ascaris Suum

Common in pigs, size ranges from 15-41 cm.
Previously linked to A. lumbricoides in humans.
Eggs are thick-shelled, oval, with distinct surface projections.
Life cycle involves:
- Eggs developing to infectious stages within 10 days.
- Larvae migrate through the liver, heart, and lungs, following a tracheal route back to the intestines.

Pathogenesis and Clinical Signs

Causes tissue destruction and hemorrhages, particularly in the liver and lungs.
Heavy infections can lead to death from lung damage or malnutrition due to nutrient absorption interference.
Clinical signs include pneumonia, stunted growth, and diarrhea.

Diagnosis and Treatment

Diagnosis via sputum and fecal examinations to detect larvae and eggs.
Treatment options include anthelmintics such as imidazole and various benzimidazoles.

Other Key Nematodes

Parascaris equorum: Affects equines, similar life cycle to A. suum, can cause enteritis and peritonitis.
Toxocara canis: Involves complex life cycles with potential prenatal transmission in dogs, with multiple routes of infection and significant clinical signs.
Enterobius vermicularis: Affects humans, characterized by perianal itching due to egg deposition.

Strongyloides Stercoralis

Females reproduce parthenogenetically; larvae penetrate host skin.
Life cycle includes free-living and parasitic forms.
Causes gastrointestinal erosions, weight loss, and diarrhea.

Stephanurus Dentatus

A kidney-worm of swine causing various pathologies including liver abscesses and skin nodules.
Diagnosis made via the identification of eggs in urine.

General Parasitology Concepts

Parasitism signifies a relationship benefiting the parasite at the host's expense.
Host-parasite compatibility is crucial for effective parasitism.
Pathological effects include nutrient competition, tissue damage, and diverse clinical presentations based on parasite species and host responses.

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Description

Explore the intricate anatomy of nematodes, including their chemosensory organs and esophagus structures. Learn about the unique reproductive systems of both male and female nematodes, highlighting key differences and adaptations. This quiz will enhance your understanding of nematode biology and classification.