We describe a rare case of the right-sided aortic arch, the unusual origin of the main arterial vessels and the unusual courses of bilateral recurrent laryngeal nerves in a Japanese cadaver. Chiefly, the right-sided aortic arch turned to the left side from the dorsal part of the trachea and esophagus, and Kommerell's diverticulum was found at the end of the arch. The right common carotid artery arose from the end part of the ascending aorta, but the left common carotid artery arose from the proximal portion of the ascending aorta. The right subclavian artery arose from the upper edge of the aortic arch, but the left one arose from the front wall at the upper side of the ligamentum arteriosum. The right recurrent laryngeal nerve hooked around the aortic arch (but not the right subclavian artery) dorsoventrally, and the left recurrent laryngeal nerve hooked around the ligamentum arteriosum and arose from the ventral side (but not dorsal) of the aortic arch. These variations are very rare, and understanding them is useful and important for clinical research.
Summary: This paper discusses muscle phylogeny based on muscle innervation and defends a new concept of nervemuscle specificity. Some researchers argued strongly against this concept in the first half of this century. However, we think their arguments were partially based on insufficiently examined findings of the ramification manner of the radial nerve. We have dissected 140 limbs of 25 species in mammals and reptiles to examine the manners of ramification of nerves supplying the forearm extensors. The pattern of the radial nerve has been revealed to consist of consistent and inconsistent elements. The branches to the forearm extensors except for the supinator follow quite consistent patterns, while the branch(es) to the muscle is much less consistent. Comparing the ramification patterns of the nerves between mammals and lizards, it can be concluded that the radial nerve in mammals is formed by the phylogenetic path alteration of its partial nerve fibers from the pathway along the flexor side in lizards to the route in the extensor side.
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