Most of the time, while you’re just breathing and not swallowing, the larynx (voice box) blocks the entrance to the esophagus. When a mouthful of food or drink is ready to be swallowed, the larynx has to rise out of the way, both to allow access to the esophagus and to close off the windpipe and prevent the food from “going down the wrong way.”

To allow this to happen, the bolus is held momentarily at the back of the tongue, a sort of anatomical metering light. If, as a result of dysphagia, the larynx doesn’t move quickly enough, the food can head down the windpipe instead. This is, obviously, a choking hazard. More sinisterly, inhaled food and drink can deliver a troublesome load of bacteria. Infection can set in and progress to pneumonia.

A less lethal and more entertaining swallowing misstep is nasal regurgitation. Here the soft palate — home turf of the uvula, that queer little oral stalactite — fails to seal the opening to the nasal cavity. This leaves milk, say, or chewed peas in peril of being horked out the nostrils. Nasal regurgitation is more common with children, because they are often laughing while eating and because their swallowing mechanism isn’t fully developed.

“Immature swallowing coordination” is the reason 90 percent of food-related choking deaths befall children under 5. Also contributing: immature dentition. Children grow incisors before they have molars; for a brief span of time they can bite off pieces of food but cannot chew them.

Round foods are particularly treacherous because they match the shape of the trachea. If a grape goes down the wrong way, it blocks the tube so completely that no breath can be drawn around it. Hot dogs, grapes and round candies take the top three slots in a list of killer foods published in the July 2008 issue of The International Journal of Pediatric Otorhinolaryngology (itself a calamitous mouthful). A candy called Lychee Mini Fruity Gels has killed enough times for the Food and Drug Administration to have banned its import.

The safest foods, of course, are those that arrive on the plate pre-moistened and machine-masticated, leaving little for your own built-in processor to do. They are also, generally speaking, the least popular. Mushy food is a form of sensory deprivation. In the same way that a dark, silent room will eventually drive you to hallucinate, the mind rebels against bland, single-texture foods, edibles that do not engage the oral device.

Those who can chew want to chew. We especially enjoy crunch. A colleague of Dr. Van der Bilt, Ton van Vliet, has spent the past seven years figuring out just how crunch works.