My book states this - The cells produce mucus that traps particles of dirt and bacteria in the air breathed in. The cilia on these cells move this debris up the trachea and into the stomach. Isn't the stomach below the trachea? Wouldn't it move the dirt and debris up the throat so it can be removed via the mouth? My book does also state that the debris is pushed up the throat as well so does it do both?
There are two pipes from your throat, downwards. A foodpipe and a windpipe. One, called the trachea, feeds air into the lungs, i.e. connects your head with your lungs. Another pipe, called the esophagus, leads to the stomach.
Both pipes meet and share the same passageway in your throat and oral/nasal cavities. Let's call this the common pipe.
The lining of the trachea, made up of ciliated cells and mucus-producing cells, does indeed move debris UP and OUT of the trachea, away from the lungs. Once this debris is at the common pipe, it can go to the stomach or into the mouth or into your nose for clearance.