Dissecting starfish is fun but often frustrating, especially when working with preserved specimens.  The following pictures are of a typical, CHEAP, preserved starfish: the kind my students usually end up dissecting.

Here's a dorsal view showing the madreporite (sieve plate).

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This is a closer view of the madreporite and the anal area.

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The pedicellariae are very tiny clawlike structures that help keep this echinoderm's skin clean.

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Here's a ventral view showing the mouth area and the ambulacral groove where the tube feet are found.

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This is a closeup of the mouth area showing the ends of the tube feet.

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Here's what the end of a cut-off arm looks like.  It's pretty difficult to distinguish the structures in a preserved specimen like this one.

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With the top removed, you can see the stomach and digestive glands.

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Remove the stomach and glands to see the ring and radial canals of the water vascular system.

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A closeup of the opened arm shows the ampullae that are the top ends of the tube foot structures.

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