Ch.2 Nematoda - Class 1 Roundworms Flashcards

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Questions and Answers

Nematodes comprise the group of organisms containing the largest number of what?

helminth parasites of humans

What are some characteristics of roundworms?

They are unsegmented, bilaterally symmetrical, and exhibit great variation in their life cycles.

Nematodes are referred to as roundworms because they are round when viewed in?

cross-section

The male nematode is usually ________________ than the female nematode.

smaller Signup and view all the answers

What does the male nematode look like?

The male often has a curved or coiled posterior end with copulatory spicules and may have oral hooks, teeth, or plates in the buccal capsule. Signup and view all the answers

Generally how long do roundworms live?

1-30+ years Signup and view all the answers

Nematodes have which two stages in their life cycle?

Both free-living and parasitic stages Signup and view all the answers

How long can a roundworm be?

some can be quite large, reaching significant lengths Signup and view all the answers

How do male worms typically appear?

Frequently have a curved or coiled posterior end with copulatory spicules. Signup and view all the answers

The adult anterior end may have what for attachment?

Hooks, teeth, or cutting plates in the buccal cavity. Signup and view all the answers

The outer body surface of a roundworm is a ___, their is underneath that.

cuticle, muscle layers Signup and view all the answers

What organs do male roundworms possess?

Testes, vas deferens, seminal vesicle, and an ejaculatory duct. Signup and view all the answers

What organs do female roundworms possess?

Ovaries, oviduct, seminal receptacle, uterus, and vagina. Signup and view all the answers

Both roundworm sexes have what?

A complex nerve cord, a well-developed digestive system, and complete reproductive organs. Signup and view all the answers

Who are the definitive hosts for roundworms?

Humans Signup and view all the answers

What can potentially be the intermediate hosts/vectors for roundworms?

Arthropods may serve as intermediate hosts and/or vectors. Signup and view all the answers

What do adult female roundworms produce?

Fertilized eggs or larvae which may be infective to new hosts. Signup and view all the answers

Eggs may be ___ after ingestion by humans.

immediately infective Signup and view all the answers

Eggs or larvae require a period of development in the environment to become?

infective Signup and view all the answers

How are eggs or larvae transmitted to a new host?

By an insect. Signup and view all the answers

Developing larvae go through a series of 4 molts with the third stage, the filariform larva, most often being the?

infective stage. Signup and view all the answers

Infections with roundworms can occur by ingestion of infective eggs or larvae, by?

Larval penetration of skin, or by transmission of larvae through insect bite. Signup and view all the answers

About one-half of the nematodes parasitic for man are intestinal; the others are found in?

various tissues. Signup and view all the answers

What may be the pathogenicity of intestinal nematodes due to?

<ol> <li>Larval migration through tissue, 2) Piercing of intestinal wall, 3) Blood loss, or 4) Allergic reactions to secretions of adults or larvae.</li> </ol> Signup and view all the answers

What are filariform larvae?

The 3rd or infective stage; long, thread-like; designed for penetration. Signup and view all the answers

What are rhabditiform larvae characterized by?

The presence of a muscular esophagus and bulbular pharynx. Signup and view all the answers

What is the general life cycle of intestinal nematodes?

Humans ingest infective eggs. Larvae hatch in intestine. Male and female adults develop in the intestine. Signup and view all the answers

Study Notes

Nematodes Overview

Nematodes are the largest group of helminth parasites affecting humans.
Roundworms are unsegmented, bilaterally symmetrical, and exhibit diverse life cycles.

Morphology and Anatomy

Roundworms have a circular cross-section, giving them their name.
Male nematodes are typically smaller than females.
Males have a coiled posterior end featuring copulatory spicules and sometimes a bursa.
Adult nematodes may possess oral hooks, teeth, or plates for attachment in the buccal cavity.
The outer body is covered by a cuticle, with muscle layers beneath.

Reproductive Structures

Male roundworms contain testes, vas deferens, seminal vesicle, and ejaculatory duct.
Female roundworms possess ovaries, oviducts, seminal receptacle, uterus, and vagina.
Both sexes have a complex nerve cord and a developed digestive system.

Hosts and Lifecycle

Humans serve as the definitive host for roundworms.
Arthropods can act as intermediate hosts or vectors; however, many nematodes do not require an intermediate host.
Female roundworms produce fertilized eggs or larvae that can be infective to new hosts.

Infectivity and Development

Eggs can be immediately infective upon ingestion by humans.
Some eggs or larvae require environmental development to become infective.
Transmission to new hosts occurs primarily through insects.

Infection Dynamics

Developing larvae undergo four molts, with the third stage (filariform larva) being the infective form.
Infections can arise from ingestion of infective eggs or larvae, larval skin penetration, or larvae transmitted via insect bites.
Approximately half of the nematodes parasitizing humans are intestinal; the remainder inhabit various tissues.

Pathogenicity

The pathogenicity of intestinal nematodes may be linked to:
- Larval migration through tissues.
- Piercing of the intestinal wall.
- Blood loss.
- Allergic reactions to adult or larval secretions.

Larval Types

Filariform larvae are long and thread-like, specialized for penetration.
Rhabditiform larvae have a muscular esophagus and bulbular pharynx, emerging from the egg.

Life Cycle of Intestinal Nematodes

Adult nematodes develop in the intestine after humans ingest infective eggs.
Exceptions like hookworms and Strongyloides stercoralis involve skin penetration by filariform larvae.
After hatching in the intestine, adults mature and contribute to a heart-lung cycle before returning to the intestine to mature.

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Description

Test your knowledge on Nematodes, the roundworms that are known for being significant helminth parasites of humans. This quiz includes key characteristics and facts about their fascinating life cycles. Perfect for students learning about this diverse and essential group of organisms.