FIGURE 2.4. The recurrent laryngeal nerve branches from the spinal cord and sends nerve impulses to the
vocal cords, as well as to other parts of the esophagus (digestive tube) and trachea (breathing tube). During
embryology, it is associated with the front part of the gills in a fish, so it loops over the aorta, the artery that
supplies most of the blood to be pumped by your heart. But fish don’t have necks, so this pathway is short. In
fish, it travels from the brain past the heart to the gills. For humans, this same nerve must loop from the spinal
column at the base of the head, down through the neck and to the heart, where it still loops around the aorta,
then back up through the neck to reach the throat, where it controls your voice box. In a giraffe, the nerve
branches out from the spinal column just below the head. It then must travel more than 7 feet down the neck,
where it can loop around the aorta, and then 7 more feet back up the neck to reach the throat region and control
the vocal cords and other parts of the esophagus and trachea. That’s a total of 15 feet of unnecessary length!
elliott
(Elliott)
#1