Nematodes: General Characteristics
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Questions and Answers

What is the characteristic of nematodes regarding their sexes?

  • They can be either male or female, or both.
  • They have separate sexes, and can only be male or female. (correct)
  • They have separate sexes, but can change from one to another.
  • They are hermaphrodites, having both male and female reproductive organs.
  • What is the function of spicules in nematodes?

  • They are used for sensing the environment.
  • They are used for movement and locomotion.
  • They are used for reproduction. (correct)
  • They are used for digestion.
  • Which of the following nematodes lays immature/nonembryonated eggs?

  • E. vermicularis
  • S. stercoralis
  • T. spiralis
  • A. lumbricoides (correct)
  • Which classification of nematodes is characterized by the presence of caudal chemoreceptors?

    <p>Phasmids</p> Signup and view all the answers

    Which of the following nematodes is found in the small intestine?

    <p>C. philippinensis</p> Signup and view all the answers

    What is the term for nematodes that do not lay eggs, but instead produce larvae?

    <p>Viviparous/Larviparous</p> Signup and view all the answers

    What is the life cycle stage that is considered the most infective for many species?

    <p>L3</p> Signup and view all the answers

    Which stage does the larva molt to become after L2?

    <p>L3</p> Signup and view all the answers

    Which nematode lays the most eggs per day?

    <p>Ascaris lumbricoides</p> Signup and view all the answers

    Which layer of the Ascaris egg shell is described as lecithin membran?

    <p>Inner Vitelline Membrane</p> Signup and view all the answers

    Which nematode is known as the largest intestinal nematode?

    <p>Ascaris lumbricoides</p> Signup and view all the answers

    What is the pathology caused by Ascaris lumbricoides known as?

    <p>Ascariasis</p> Signup and view all the answers

    Study Notes

    Trichiura Mnemonic: C.A.S.H. & T

    • Trichiura: Extraintestinal Nematodes that affect Muscle, Lymph Nodes, Subcutaneous Tissues, Eyes, and Meninges
    • Trichiura life cycle: L1 and L2 (Rhabditiform larva), L3 (Filariform larva)

    Filarial Worms

    • Lifecycle: Larval stage has three stages: L1 and L2 (Rhabditiform larva), L3 (Filariform larva)
    • Developmental cycle: Molting (outgrowing and casting off old cuticle), Synthesis (creating new cuticle), Exsheathment (casting off old cuticle)

    A. Cantonensis

    • Life cycle: Eggs, L1, L2, L3, L4, Adult
    • Infective stage: L3 stage
    • Not all parasites have an L4 stage; medically important nematodes stop at L3

    Intestinal Nematodes

    Ascaris Lumbricoides

    • Most common intestinal parasite in humans in the Philippines
    • Largest intestinal nematode
    • Adults lay 200,000 eggs per day
    • Eggs become infective 2-6 weeks after deposition
    • Egg characteristics: 85-95 micrometers length, 38-45 micrometers width, with layers (Vitelline membrane, glycogen, and mammillation)
    • Stages: Unfertilized, Fertilized Corticated, Fertilized Decorticated, Embryonated
    • Adult worm: Anterior head has trilobate lips, Pointed posterior tail in females, Curved posterior tail in males
    • Pathology: Ascariasis, Member of the 'Unholy Three', Loeffler's pneumonia

    Nematodes

    • Characteristics: Elongated, cylindrical, bilaterally symmetrical, Unsegmented, Complete digestive system, No circulatory system, Dioecious
    • Reproduction: Oviparous (lays immature eggs), Oviviparous (lays mature eggs), Viviparous/Larviparous (lays larva)
    • Chemoreceptors: Amphids (cephalic), Phasmids (caudal)
    • Classification: Phasmids (Subclass Secernentia), Aphasmids (Class Adenophorea)
    • Habitat: Small intestine (C. philippinensis, A. lumbricoides, Hookworms), Large intestine (T. spiralis adult, E. vermicularis)

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    Description

    Learn about the general characteristics of nematodes, also known as roundworms. Understand their elongated, cylindrical body, complete digestive system, and dioecious nature. Explore the distinctions between male and female nematodes and their reproductive strategies.

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