Platyhelminthes: Class Cestoda Overview

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Questions and Answers

What is the primary characteristic of cestodes mentioned in the content?

They utilize a single host for their entire life cycle.

They have a segmented body.

They are exclusively found in aquatic environments.

They bear a linear series of reproductive units called proglottids. (correct)

Which of the following is true about the reproductive traits of most cestodes?

They are hermaphroditic and often require multiple hosts. (correct)

They require only one host for reproduction.

They are dioecious organisms.

They reproduce asexually without the need for a host.

What is an example of a cestode mentioned in the content?

Ascaris lumbricoides

Schistosoma mansoni

Echinococcus granulosus

Taenia saginata (correct)

Where does Taenia saginata primarily live as an adult?

In the human intestine Signup and view all the answers

What structure is composed of a linear series of reproductive units in cestodes?

Proglottids Signup and view all the answers

What is the function of the vasa efferentia in the male reproductive system?

To connect the testes to the vas deferens Signup and view all the answers

Which component directly connects multiple testes to the vas deferens?

Vasa efferentia Signup and view all the answers

Which statement best describes the organization of the male reproductive system's testes?

They are numerous and scattered Signup and view all the answers

What does the vas deferens primarily do in the male reproductive system?

Transport sperm to the ejaculatory duct Signup and view all the answers

How are the testes connected to each other in the male reproductive system?

By the vasa efferentia Signup and view all the answers

What components make up the excretory system described?

Flame cells and canals Signup and view all the answers

What structure continues from the excretory canals in the scolex?

A pair of dorsolateral excretory canals Signup and view all the answers

Which pair of excretory canals is mentioned as part of the system?

Dorsolateral and ventrolateral Signup and view all the answers

What is the primary function of flame cells in the excretory system?

Excretion of waste Signup and view all the answers

Where are the excretory canals located relative to the body form?

Along the length of the body Signup and view all the answers

What role does the intermediate host play in the life cycle described?

It develops the larval stages. Signup and view all the answers

In which part of the reproductive system does fertilization occur?

In the lower part of the oviduct. Signup and view all the answers

What is the outcome of the life cycle involving the essential host?

Sexual reproduction. Signup and view all the answers

How many hosts are involved in the life cycle as described?

Two hosts, one for larval development and one for reproduction. Signup and view all the answers

Which statement best describes the movement of sperm during fertilization?

Sperms move from the vagina to the lower part of the oviduct. Signup and view all the answers

How long does it take for a mature tapeworm to develop in a human host?

2-3 weeks Signup and view all the answers

What happens to proglottids when a person is infected with a tapeworm?

They are expelled from the intestine Signup and view all the answers

What is the primary consequence of being infected with one of these tapeworms?

Regular expulsion of proglottids Signup and view all the answers

Which of the following accurately describes the lifecycle of a tapeworm in humans?

It forms a mature worm, and then begins releasing proglottids Signup and view all the answers

What is the significance of proglottids for a tapeworm’s reproduction?

They contain eggs for reproduction Signup and view all the answers

What happens to the egg shells after the cattle swallows the eggs or proglottides?

They are dissolved in the intestine. Signup and view all the answers

Where do the hexacanth embryos burrow after the cattle swallows the eggs?

Through the intestinal wall into blood or lymph vessels. Signup and view all the answers

Which of the following best describes hexacanth embryos?

They are the initial stage after egg shell dissolution. Signup and view all the answers

Which process initiates after cattle consume the eggs or proglottides?

Dissolution of egg shells in the intestine. Signup and view all the answers

What role do blood or lymph vessels play in the life cycle of the hexacanth embryos?

They facilitate movement to other tissues. Signup and view all the answers

Study Notes

Platyhelminthes Subkingdom Metazoa

Subkingdom: Metazoa
Phylum: Platyhelminthes
Classes: Turbellaria, Trematoda, Cestoda

Class Turbellaria

Example: Planaria
1-Class

Class Trematoda

Example: Fasciola
2-Class

Class Cestoda

Example: Taenia
3-Class

Characteristics of Class Cestoda

Endoparasites: Lack an alimentary canal
Absorb nutrients through body surface
Long flat worms: Composed of linear proglottids (reproductive units)
Most are hermaphrodites: Require at least two hosts (e.g., Taenia saginata lives as adult in human intestines)
Mature adult can reach 10-12 meters in length
Can have 1000-2000 proglottids

Cestoda Body Regions

Scolex: Bears hooks, suckers, or other attachment organs
Neck: Narrow, unsegmented region followed by a linear series of proglottids (immature, mature, and gravid).

Life Cycle

Complicated, involving one intermediate host and one essential host
Intermediate host harbors larval stages
Essential host harbors mature stages (sexual reproduction)
Humans are an essential host for some tapeworm species

Excretory System

Composed of flame cells attached to small canals leading to excretory canals
Excretory canals in scolex continue along body
Paired dorsolateral and ventrolateral excretory canals connected by transverse canals near posterior end of each proglottid

Reproductive System

Hermaphrodites: Each proglottid has both male and female genital systems
Male reproductive system: Numerous small testes connected to vasa efferentia, forming a single vas deferens that leads into a seminal vesicle and opens through a papilla-like penis.
Female reproductive system: A large bilobed ovary connected to the oviduct, which unites with the vitelline duct to form an ootype. The uterus is branched in gravid proglottids, and filled with fertilized eggs.

Taenia Saginata

A type of tapeworm
Has a uterus (branched), testes, ova, and other relevant structures for reproduction
Mentioned in life cycle descriptions

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Description

Explore the fascinating characteristics and life cycle of Class Cestoda, a group of flatworms under the subkingdom Metazoa. Learn about their structures, such as the scolex and proglottids, and their unique reproductive strategies. This quiz will test your knowledge on these endoparasitic organisms and their biological significance.