Observations on the physiology of the larynx / by John Wyllie, M.D.

  • Wyllie, John.
Date:
1866
Catalogue details

Licence: Public Domain Mark

Credit: Observations on the physiology of the larynx / by John Wyllie, M.D. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    upon the corresponding saddle-shaped surface of the cricoid. This joint is so oblique, that when the arytenoids are rotated upon it, they naturally approach each other in the middle line, so that their internal edges and vocal processes are brought into apposition. Owing to the articular surface being situated on the inferior aspect of the projecting posterior angle, the whole body of the cartilage extends forwards and assists in covering the opening of the larynx. The concave posterior surfaces being anterior to the articulations, it necessarily follows that the arytenoid muscle, to which they give attachment, must of itself be sufficient to pull the cartilages with their processus vocales together in the middle line. The mechanism by which the true cords are approximated is thus comparatively simple. Three muscles are said to take part in the action. The arytenoid pulls the cartilages together, bringing their internal edges in contact, so as to close the so-called respiratory portion of the glottis; the thyro- and crico-arytenoids, whilst they assist the other, act more particularly by rotating the cartilages inwards, so as to bring their anterior processes into still closer apposition, and also to lower them in the cavity of the larynx. This last action must especially be accomplished by the fibres of the thyro-arytenoid, which, as already mentioned, are attached along the outer edge, almost as high as the apex of each cartilage. It is not so easy to determine by wdiat means the false cords are brought together. We have already seen that the point to which most of their fibres are attached posteriorly, is a pit about the middle of the anterior convex surface of each arytenoid cartilage, and, therefore, to the outer side of, and superior to, the insertion of the true ligaments. But this is not their only posterior connexion ; another strong band of their fibres becomes attached to the apex of the cartilage of Wrisberg, a body which is too much overlooked by anatomists. Anteriorly, besides their tliyroid attachments, they send upwards and forwards several processes to the edge of the lower thickened portion of the epiglottis. There is also to be observed, stretching between the margin of that valve and the superior border of each false ligament, in its whole length, a thin layer of muscular fibre connected with the aryteno-epiglottic muscle. The cartilages of Wrisberg are contained within the aryteno- epiglottic folds of the mucous membrane, lying immediately in front of, and parallel to the inner edge of the arytenoid cartilage on each side. They are very slender, except at their upper end, where they form in the free edge of the aryteno-epiglottic fold, a rounded eminence, which is often mistaken for the apex of the arytenoid cartilage. It, says Ecker, is surrounded by mucous glands, from it along the false cords a horizontal process runs forwards, which one sees radiate between the elastic fibres of these cords. In front of the inner edge of each arytenoid, the position of this cartilage is marked by a slightly prominent line on the mucous ^ Ecker's Icones Physiologicse.