Don't compare them to the simple rubber suction cups on kids' toy dart guns; these have their own elaborate muscular regulatory mechanisms. This diagram illustrates the internal structure of a single octopus sucker.

There are two main regions, an infundibulum (IN) on the attachment face of the sucker, and a deeper chamber called the acetabulum (A) (if you don't recall any Latin, "infundibulum" just means "funnel", while "acetabulum" is "vinegar cup"â anatomy is littered with funnels and cup-shaped structures, so these are actually very generic names).