Porta

For the Forerunner artifact, see Portal. A Porta is a sphincter-like orifice embedded into the floors and walls of Flood Hives that acts as the Flood analog to doorways. Portas were sighted in the Flood-infested High Charity and in the Halo 3 multiplayer map, Isolation.

Trivia

 * Portas have at least two 7 references in them, one being that Portas are made up of seven segments, and the other being the fact that there are seven Portas on the level, Cortana.
 * The name "porta" probably comes from the Greek word porta (πόρτα), which means "door".
 * On the Halo 3 multiplayer map Isolation there is one Porta. Sliding down a hole on the top part of the map will lead you to slide down a tube. A Porta will open, letting you into the Flood-infested cave.
 * Portas make an appearance in Halo Wars, on the Flood Barracks.
 * There is a running joke among gamers that the Portas are the Gravemind's intestinal openings, due to their sphincter-like appearance.