In humans each lung is encased in a thin membranous sac called the pleura, and each is connected with the trachea (windpipe) by its main bronchus (large air passageway) and with the heart by the pulmonary arteries.
Belize's forest-clad highlands sit atop Central America's most extensive cave system, containing some of the largest subterranean passageways and chamber rooms in the western hemisphere.
Authorities say El Chapo escaped through a narrow tunnel cut into his shower stall, which led to a large, elaborate passageway more than a mile long with ventilation, lighting, and a motorcycle built onto rails.
Scaffolding poles can be used to prop up the ceiling, but this approach should not be trusted to secure larger rooms, only passageways.
It's a massive three-story concrete-and-glass structure, with large rooms and outdoor passageways.
"You know, the secret passageways, the large towers, the drawbridges," DeClements says.
Larger pillars mean smaller passageways, said Stephen Dmytriw, a civil engineer in the safety and health program at the Colorado School of Mines.
Compared with the internal circuitry, this passageway requires relatively large amounts of power.
The permanent PATH terminal and its surrounding network of passageways carries the largest price tag of any of these projects: up to $2 billion, financed with $1.7 billion from the Federal Transit Administration and $300 million in insurance proceeds.
The courtyard provides much of the natural light, as numerous large windows, doors and glass-enclosed passageways on both levels open up to it.
