When a person receives a limb donation, how do surgeons “wire up” the nerves so that the recipient can use the limb and feel sensation from it?
In: Biology
A subject I have personal experience with!
I broke my humerus playing roller derby a few years back and the fracture severed my radial nerve, meaning I lost the ability to lift my wrist and extend my fingers.
As other posters have noted your nerves are protected by a myelin sheath, which is basically a tube around the actual nerve. If you think about your cell phone charging cable the nerve is like the metal wire inside that carries the electrical current and the myelin sheath is like the materials covering and insulating it.
When a nerve is damaged the entire portion of the nerve from the point of damage to the termination (or “end”) dies as well. As long as the myelin sheath remains intact or heals properly the nerve will begin to regrow from the point of damage to the termination point.
So when performing a transplant or reconstructive surgery all the surgeons can do is connect these tubes and wait for the nerve to regenerate within.
Nerves grow very slowly, about 1 inch per month. The radial nerve which I severed in my accident invenerates the hand muscles at the top of your forearm. There was approximately six inches between this point and the damage site so it took about six months to fully regain control of my hand functions.
As far as I know this only applies to nerves branching off the spinal column. The spinal nerve itself will not regenerate or heal itself in most circumstances, which is why spinal injuries usually result in permanent disabilities.
But long story short, we can’t directly correct the nervous system through surgery or other intervention, we can only manipulate the tubes in which the nerves reside and wait for the nerves to repair themselves.
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