....opening?
A fissure is an opening or crack in the Earth's crust, typically where tectonic plates meet. It is not a projection or depression, but rather a narrow, long fracture in the ground.
A meatus is an opening; therefor, it's a depression, not a projection.
projection
projection
projection
projection
is a depression
A sulcus is a depression or fissure in the surface of the brain.
"A crest is a projection or ridge, especially of bone; cresta"source: chacha.com
projection. The bumps of bone around your knees and elbows are almost all called condyles.
A long crack from which lava flows through is called a fissure. These fissures can be found along volcanic zones and can release lava during volcanic eruptions.
A fissure is a crack-like sore.Fissure.