ClipArt ETC
In this simple sponge, water enters minute holes in the sides and passes out of the opening at the top of the tube.

Sponge

In this simple sponge, water enters minute holes in the sides and passes out of the opening at the top…

In this simple sponge, part of the outer wall is cut away to show the inside.

Sponge

In this simple sponge, part of the outer wall is cut away to show the inside.

A cross-section of a simple tubular sponge.

Sponge

A cross-section of a simple tubular sponge.

A diagram of a commercial sponge.

Sponge

A diagram of a commercial sponge.