STUDIES ON THE NERVE INNEVATION OF THE LARYNX

Part I The Peripheral Distribution of Laryngeal Nerve of the Dog

Abstract

Content;
The peripheral distribution of the superior and inferior laryngeal nerves of 47 grown-up dogs were dissected and examined by means of an oto-micro- scope. The findings are as following;
1. The internal branch of the superior laryn- geal nerve of a dog consists chiefly of sensory fibers. It divides itself into two superior and inferior branches outside of the larynx, and afte- rwards the superior banch divides itself farther into two branches.
One of these branches spreads among the muco- us membrane of epiglottis and the other divides chiefly among arytenoide mucous membrane. The inferior twig of the internal branch ramifies in the mucous membrane of larynx and makes an anasto- mosis with posterior branch of the recurrent lary- ngeal nerve. This is the so-called Galen's anasto- mosis.
2. The external branch of the superior laryn- geal nerve contains for the most part motor nerve fibers. They divide themselve into two terminal twigs and is distributed among the cricothyroid muscle, (pars recta and pars obliqua).
3. The recurrent nerve divides itself into ant- erior and posterior branch at the level of the lower margin of cricoid cartilage outside of the larynx. The anterior branch, which is considered chiefly as motor nerve divides immediately after ramifica- tion. This middle twig distributes in the posterior crico-arytenoid muscle. The anterior branch, then, penetrates into the laryx, and gives a twig for transversal arytenoid muscle and lateral crico- arytenoid muscle. Lastly the branch distributes itself among the vocal cord, (the thyroarytenoid muscle).
The location of nerve penetration into the vocal cord is nearly the spot, 2/3 length of the vocal cord distent from the anterior commissure, that is, 1/3 length of the vocal cord from the posterior commissure. The ramification of nerve fibers in the thyro-arytenoid musclesis so complicated, that internal and external thyro-arytenoid muscle couldnot be distinguished by means of nerve supply. The posterior branch of the recurrent nerve, which is regarded chiefly as sensory, makes a so-called Galen's anastomosis combined with the interior twig of the internal branch of the superior laryn- geal nerve.
4. Each Galen's anastomosis ramifies on it's way, with 5 or 6 branches for the mucous membr- ane of the entrance for esophagus. One of these branches, (second twig from below) of the both sides makes an anastomoses in the anterior wall of esophagus at the level between arytenoid cartilage and cricoid cartilage.
5. Para-recurrent nerve spreads, on its way, into 12 to 16 branches for tracheal and esophageal mucous membrane, and also makes anastomoses with recurrent nerve. Some of these branches pen- etrate into larynx, but they all terminate in the mucous membrane, and are probably sensory bran- ches.