NEM 10V Lecture Notes - Lecture 29: Nematology, Gastrovascular Cavity, Taenia Solium
Nematology
Part 3 Platyhelminthes (Flat worms):
• Flatworm is the common name for invertebrates in the Phylum Platyhelminthes. They are
divided into three different groups.
• One group is the free-living Turbellaria.
• The other two groups contain parasites that can have devastating effects on the health of
domestic animals and humans.
• Platyhelminthes are the first group we have studied to have bilateral symmetry, having
right and left halves that are mirror images.
• They have distinguishable head and tail regions (known as cephalization), and are also
the first group to have 3 distinct tissue layers, an outer ectoderm, a middle layer of
mesoderm, and an inner layer of endoderm.
• Note that they do not have a body cavity (coelom), and that tissue called mesenchyme
fills the area between the muscle layer and the digestive tract.
• They digest their food inside a highly branched saclike gut called a gastrovascular cavity.
Food enters this cavity through the same opening that expels wastes, and the cavity also
functions in gas exchange.
• The Cestoda are commonly known at tapeworms. There are many different species of
tapeworm that commonly infest the digestive tract of their hosts. Adults consist of a head
that is used for attachment, followed by a neck and a chain of continuously forming
segments called proglottids.
• Each proglottid is an independent unit containing both male and female reproductive
organs (hermaphroditic). When mature, each proglottid contains hundreds of eggs.
Proglottids are shed in the host’s feces.
• An intermediate host becomes infested from eating the feces. Examples of intermediate
hosts are a flea for the dog tapeworm, and a pig for the pork tapeworm. The intermediate
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Document Summary
Part 3 platyhelminthes (flat worms): flatworm is the common name for invertebrates in the phylum platyhelminthes. They are divided into three different groups: one group is the free-living turbellaria. Food enters this cavity through the same opening that expels wastes, and the cavity also functions in gas exchange: the cestoda are commonly known at tapeworms. There are many different species of tapeworm that commonly infest the digestive tract of their hosts. Adults consist of a head that is used for attachment, followed by a neck and a chain of continuously forming segments called proglottids: each proglottid is an independent unit containing both male and female reproductive organs (hermaphroditic). When mature, each proglottid contains hundreds of eggs. An intermediate host becomes infested from eating the feces. Examples of intermediate hosts are a flea for the dog tapeworm, and a pig for the pork tapeworm. The intermediate host then passes the juvenile stage of the tapeworm to the final host.
