Richard Dawkins Demonstrates Laryngeal Nerve of the Giraffe

blindwatcher
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Richard Dawkins demonstrates laryngeal nerve of the giraffe as proof of natural selection.

75 comments

if the recurrent laryngeal nerve innervates the trachea and esophagus, then what's wrong with it branching off at the aorta from the vagus to innervate the entire stretch of neck? Ultimately, it WILL have to extend long enough to innervate the entire neck, regardless of at which point it branches off from the vagus nerve.

If, however, only the larynx is being innervated, then yes, i would agree that the U-turn doesn't make sense...
By 180SQN 3 years ago
Actually, just to clarify: isn't it the vagus nerve that travels from the neck down toward the heart, and then the recurrent laryngeal nerve branches off from the vagus just below the aorta?
By 180SQN 3 years ago
No, it doesn't. It would make sense to send a branch off to innervate the larynx on the way down. Not go down to the heart, make a U-turn and then head back up. I really hope you're not an engineer or in anyway involved with the next shuttle mission...
By scudmuncher 3 years ago
If the recurrent laryngeal nerve also innervates the cardiac plexus, esophagus and trachea, then it makes sense for the nerve to travel down an entire stretch of neck.

sources:
1. http://en.wikipedia.org/wiki/Recurrent_laryngeal_nerve
2. http://en.wikipedia.org/wiki/Parasympathetic_nervous_system
By 180SQN 3 years ago
As the recurrent nerve hooks around the subclavian artery or aorta, it gives off several cardiac filaments to the deep part of the cardiac plexus. As it ascends in the neck it gives off branches, more numerous on the left than on the right side, to the mucous membrane and muscular coat of the oesophagus; branches to the mucous membrane and muscular fibers of the trachea; and some pharyngeal filaments to the superior pharyngeal constrictor muscle.From the left vagus nerve the recurrent laryngeal nerve hooks around the aorta to travel back up to the larynx and proximal esophagus while, from the right vagus nerve, the recurrent laryngeal nerve hooks around the right subclavian artery to travel back up to the same location as its counterpart. These different paths are a direct result of embryological development of the circulatory system. Each recurrent laryngeal nerve supplies the trachea and the esophagus with parasympathetic secretomotor innervation for glands associated with them
By 180SQN 3 years ago