air, water, and plant roots.
tunnels
an earthworm makes tunnels in the ground and keeps it moist.So it wont dry out.
It has just over 151.34 miles (243.56 km) of mapped passageways.
because when dig tunnels soil gets air water etc
It is because the house was a stop in the moving of slaves. The passageways helped keep the slaves safe from the slave catchers or bounty hunters who wanted to return them to their slave owner
Spinal Nerves
deep mining
provide passageways for spinal nerves that proceed between joining vertebrae and connect to the spinal cord.
Tunnels are long underground passageways that carry highways, railroads, and pipelines under mountains, seas, and rivers.The tunnel was drilled right through the mountains so cars and trucks could pass through. Tunnels can be built underground to carry people. Tunnels are also built to carry waste water away from the city.
They provide passageways for blood vessels to enter the bone.
Both bridges and tunnels are man-made to provide a way to get to a point that would otherwise be difficult or impossible to get to.
Caves! As simple as that. And the passageways are just "passages", believe it or not - though that is a generic term for different passage types have their own technical names (apart from any lyrical names for individual ones).