recurrent laryngeal nerve

Evidence against “intelligent design” Example 1: The Recurrent Laryngeal Nerves.

The Recurrent Laryngeal Nerve (RLN) is a pair of nerves that decent from the brain, down the neck, and loop around the major aorta of the heart before making their way up to the larynx. If you were an all-knowing creator, would you “wire” your creations in such a needlessly complicated way? Why not just go right from the brain to the larynx?
But of course, there is no all-knowing creator, and the trail traveled by the RLN is the result of fish. “But Austin, what do fish have to do with anything?” You may be asking yourself. Well, all tetrapods are evolutionarily descended from fish, and in the anatomy of fish the route of the RLN makes sense. Fish don’t have much in the way of a neck, you see, so the RLN only must make a short jot around the aorta to get to the larynx. But over time, the proto-tetrapods began to gain a neck, and the RLN found itself “stuck” on the wrong side of the aorta as the head moved further from the torso. Now evolution had only one option available to it, since the RLN and aorta could not be “untied”, the RLN would have to be made longer.

So now, even in species as neck-y as Giraffes and Sauropods, the RLN must go all the way down to the aorta before heading back up to the larynx. If there was an all-knowing creator, surly he would have foreseen the complications of this sort of “wiring”. But evolution does not have the benefit of foresight, and the RLN shows that.

Why is left recurrent laryngeal nerve more prone to paralysis?

Anatomy of recurrent laryngeal nerve (RLN).

They are called recurrent because they follow a recurrent course, moving in the opposite direction to the nerve they branch from, a fact from which they gain their name.

Both originate from the vagus nerve of their respective sides

The right RLN leaves the right vagus nerve as it crosses the right subclavian artery and loops posteriorly under the artery. The right RLN initially traverses at an angle towards the tracheoesophageal groove and then runs parallel to it.

The left RLN originates from the left vagus nerve as it crosses the aortic arch. It then passes posteriorly under the arch and the ligamentum arteriosum. The left RNL travels in a course that is parallel and close to the tracheoesophageal groove.

The lower origin and consequently, a longer course of the left RLN makes it more vulnerable to injury than the right RLN.

dailymotion

I found this video while studying anatomy of the mediastinum.  Regardless of whether or not people believe in a God, I just can’t fathom how people don’t see evolution as the primary theory to explain our form.  Maybe that is just the scientist in me.

(I am going to bang my head against the wall later for all the debate this causes) 

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Evolution of the Recurrent laryngeal Nerve - proof of common descent (via LithodidMan)

Following on from the previous post, this video shows the evolution of the Laryngeal nerve in fish.