Ch. 6: Cestodes and Tapeworms

Questions and Answers

Which of the following are general characteristics of adult tapeworms? (Select all that apply)

Heteroxenous (correct)

Found in the intestinal tract (correct)

Are polyzoic

Have a digestive system

What are the body forms of adult tapeworms?

Scolex, Neck, Strobila

What is a scolex?

The anterior end of a tapeworm, bearing suckers and hooks for host attachment.

What is the neck of a tapeworm?

Area of strobilation where new proglottids form. Signup and view all the answers

What is strobila?

Sequential sections of proglottids. Signup and view all the answers

What is a proglottid?

Each segment in the strobila of a tapeworm, containing a complete sexually mature reproductive system. Signup and view all the answers

All tapeworms of medical importance are polyzoic.

True Signup and view all the answers

What is polyzoic?

A strobila consisting of more than one proglottid. Signup and view all the answers

What is monozoic?

A tapeworm whose strobila consists of a single proglottid. Signup and view all the answers

Proglottids are segmentations on the worm.

False Signup and view all the answers

What is strobilation?

New proglottids form near the neck region. Signup and view all the answers

What are the three ways of copulation after sexual maturity?

Selfing, crossing with other proglottids, crossing with other worms. Signup and view all the answers

What are the fates of proglottids?

Apolysis, pseudoapolysis, hyperapolysis. Signup and view all the answers

What is apolysis?

Proglottid detaches and passes intact or disintegrates to release eggs. Signup and view all the answers

What is pseudoapolysis?

Proglottids release eggs from proglottid through uterine pore. Signup and view all the answers

What is hyperapolysis?

Detachment of a proglottid while still immature, before eggs are formed. Signup and view all the answers

What is pseudoscolex?

Folds of strobila. Signup and view all the answers

What are the three types of sucker-like organs on or by the scolex?

Acetabula, bothridia, bothria. Signup and view all the answers

What are acetabula?

Muscular cup-shaped suckers, typically in groups of 4. Signup and view all the answers

What are bothridia?

Suckers usually in groups of 4 with highly mobile, leaf-like margins. Signup and view all the answers

What are bothria?

Shallow sucking grooves on some cestodes. Signup and view all the answers

Bothridia have the most complex nervous system.

True Signup and view all the answers

What are the characteristics of Cestode tegument?

Microtriches, syncytial layer, glycocalyx. Signup and view all the answers

What functions does the glycocalyx serve?

Enhances amylase activities, absorbs bile salts, inhibits host enzymes. Signup and view all the answers

What are calcareous corpuscles?

Acts as a buffer from organic acids, looks like sand. Signup and view all the answers

What are the characteristics of the nervous system of tapeworms?

Simplest worms have bothria; more complex ones have acetabula. Signup and view all the answers

What is a flame cell?

Specialized cell that filters and removes excess water. Signup and view all the answers

What are the reproductive characteristics of tapeworms?

Most are monoecious, some are dioecious. Signup and view all the answers

What is protandry?

A form of sequential hermaphroditism where an individual matures first as a male. Signup and view all the answers

What is protogyny?

Born a female (female organs). Signup and view all the answers

Study Notes

General Characteristics of Adult Tapeworms

Exclusively inhabit the intestinal tract of their hosts.
Possess no digestive system, relying on absorption through their skin.
Exhibit heteroxenous life cycles, often involving multiple hosts.

Body Structure of Adult Tapeworms

Comprised of three main parts: scolex (head), neck, and strobila (body).
Scolex includes structures for attachment to the host, while the strobila is formed of proglottids.

Scolex

The anterior end of the tapeworm, equipped with suckers and hooks for secure attachment to the host's intestinal wall.

Neck

The region responsible for the formation of new proglottids, with older proglottids located towards the posterior end.

Strobila

A series of segments (proglottids) that makes up the main body of the tapeworm.
Each proglottid is hermaphroditic, containing both male and female reproductive organs.

Proglottid

Represents an individual segment within the strobila that houses a complete and sexually mature reproductive system.

Polyzoic vs. Monozoic

All medically significant tapeworms are polyzoic, possessing multiple proglottids.
Monozoic tapeworms consist of a singular proglottid.

Strobilation

The process where new proglottids emerge from the neck region, promoting growth and development.

Copulation Methods

Can self-fertilize, cross-fertilize with other proglottids from the same worm, or mate with other worms by intertwining their bodies.

Fate of Proglottids

Proglottids can detach through apolysis, pseudoapolysis, or hyperapolysis, affecting egg release.

Apolysis

Involves proglottids detaching completely and either passing through the host intact or disintegrating to release eggs.

Pseudoapolysis

Eggs are released from proglottids through the uterine pore while the worm remains in the host's intestines.

Hyperapolysis

Early detachment of a proglottid before the formation of eggs occurs.

Pseudoscolex

Refers to folds of the strobila contributing to the worm's structural integrity.

Sucker-like Organs on Scolex

Includes acetabula (muscular and cup-shaped), bothridia (leaf-like, mobile margins), and bothria (shallow sucking grooves).

Acetabula

Typically arranged in groups of four; common in many tapeworm species.

Bothridia

Usually organized in fours; feature adaptable, mobile margins for effective adherence.

Bothria

Comprised of 2 to 6 shallow grooves; most commonly consist of two.

Nervous System Complexity

Bothridia are associated with the most intricate nervous system, featuring ganglia and sensory organs.

Cestode Tegument Characteristics

Microtriches enhance surface area for nutrient absorption.
Syncytial structure presents a contiguous layer of cytoplasm, devoid of separating cell membranes.
Glycocalyx, a carbohydrate layer, covers microtriches and aids in nutrient absorption.

Functions of Glycocalyx

Enhances enzymatic activities of amylase in the host.
Aids in nutrient absorption, particularly bile salts.
Inhibits digestive enzymes like trypsin and lipase, protecting the worm's tissues.

Calcareous Corpuscles

Scattered throughout larval stages, these structures act as buffers against organic acids from metabolic waste.

Nervous System Features

Simplistic worms possess bothria with one pair of cerebral ganglia.
More complex species have acetabula with multiple pairs of longitudinal nerves.

Flame Cells

Specialized cells for filtering excess water, operating through excretory canals running along the strobila.

Reproductive Characteristics

Most tapeworms are monoecious with some dioecious; each proglottid contains reproductive organs.

Protandry

A type of sequential hermaphroditism where an organism first matures as a male and later transitions to female.

Protogyny

Involves organisms born as females, possessing female reproductive organs from the outset.

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Test your knowledge on the form, function, and classification of tapeworms with these flashcards. This quiz covers key characteristics, body structure, and the anatomy of adult cestodes. Enhance your understanding of these important parasitic organisms.