What is the medical name for the voice box?

The larynx, which sits at the top of the windpipe and does two jobs, only one of which is speech. Its original and more important function is a valve: it seals the airway when you swallow, so food goes to the stomach rather than the lungs, and it seals when you lift something heavy so your chest can be pressurised.

Sound is made by air forcing the vocal folds apart and elastic recoil snapping them shut, hundreds of times a second - not by vibrating like strings but by opening and closing. Pitch depends on their length and tension, which is why male voices drop at puberty as the larynx grows, and why the change is permanent and abrupt rather than gradual.

The nerve that controls it is one of the standard examples of evolution being a bodger rather than a designer. The recurrent laryngeal nerve runs from the brain down into the chest, loops under an artery, and comes back up to the larynx - a detour of no purpose, inherited from fish ancestors where the route was direct. It is a minor absurdity in a human and a spectacular one in a giraffe, where the same nerve travels several metres down the neck and back up to reach a destination a few centimetres from where it started.