resonator
A resonator.
A resonator.
the morula develops into a hollow, fluid-filled ball of cells called a blastocyst.
ear
Question?
Most are not. Some may have hollow parts, but most are filled with lead.
cochlear duct
Gold plate is a layer of gold thinner than paper. Gold filled is made of gold, but hollow, and the hollow is filled with another metal. Gold filled has much more gold.
Hollow tubes is an redundant expression. Tubes must be hollow, by definition. However tubes can be filled with something so they are not "empty" (they still will be hollow).
epiphysis
solid.
Yes, and filled with air.