| FIG. 8. |
| Laryngeal Image during Phonation. |
| FIG. 9. |
| Laryngoscopic Diagram showing the vocal cords widely drawn apart, and the position of the various parts above and below the glottis during quiet breathing. g. e. Glosso-epiglottic fold. s. u. Upper surface of epiglottis. l. Lip or arch of epiglottis. c. Protuberance of epiglottis. v. Ventricle of the larynx. a. e. Ary-epiglottic fold. c. W. Cartilage of Wrisberg. c. S. Cartilage of Santorini. com. Arytenoid commissure. v. c. Vocal cord. v. b. Ventricular band. p. v. Processus vocalis. c. r. Cricoid cartilage. t. Rings of trachea. (From Mackenzie.) |
| FIG. 10. |
| Laryngoscopic Diagram showing the approximation of the vocal cords and arytenoid cartilages, and the position of the various parts during vocalization. f. i. Fossa innominata. h. f. Hyoid fossa. c. h. Cornu of hyoid bone. c. W. Cartilage of Wrisberg. c. S. Cartilage of Santorini. a. Arytenoid cartilages. com. Arytenoid commissure. p. v. Processus vocalis and cartilages of Seiler. (From Mackenzie.) |
The first detail to attract the eye is the epiglottis, which appears as a yellowish-red arch reaching from side to side across the image. It is thicker in the middle than at either end, and a protuberance is usually seen in the centre pointing forward. This arch is the upper margin of the epiglottis, and the protuberance is the tubercle, situated near the insertion of the epiglottis into the thyroid cartilage. The shape as well as the color of the epiglottis is very variable in different individuals, being sometimes rounded as in the drawings, sometimes rolled up like a dried leaf, sometimes notched in the centre, and sometimes presenting a point at this place. However, all these variations in shape have nothing to do with any pathological process, and may therefore be termed normal. The color of the organ also varies from a bluish-yellow to a pink-red, and these variations are also normal, being due to a greater or less thickness of the tissue covering the cartilage, which by shining through imparts its bluish color to the tissue. The superficial blood-vessels also are more prominent in some individuals than in others, and may not be noticeable in some cases.
Immediately behind the epiglottis we see two pit-like depressions, separated from each other in the middle by a fold of mucous membrane and bounded on either side by similar folds less prominent. These folds are the glosso-epiglottic ligaments, and serve to connect the tongue with the epiglottis, while the depressions are the glosso-epiglottic grooves, in which we usually find the foreign bodies which have accidentally been swallowed.
The ends of the epiglottic arch are lost in folds of mucous membrane, which run forward and inward to meet in the median line some distance in front of the epiglottis. Along their course several nodules of different size are noticed, which are symmetrically situated on either side. The one nearest to the epiglottis is the cartilage of Wrisberg, a small cartilaginous nodule imbedded in the tissue. The larger one, situated at the end of the fold of mucous membrane, is the arytenoid cartilage, and a third small nodule is noticed close to the arytenoid cartilage between it and the cartilage of Wrisberg, which is called the capitulum Santorini. The folds of mucous membrane are termed the aryteno-epiglottidean or ary-epiglottic folds. Their color is normally of a pinkish-red, and does not vary much in different individuals.
The arytenoid cartilages forming the ends of the ary-epiglottic folds are movable, approaching and separating alternately during the act of respiration, while during phonation they are pressed against each other, thus obliterating the space between them which is seen when they are separated. This space is the inter-arytenoid space or commissure, and is formed by the lateral walls of the arytenoid cartilages and the upper margin of the posterior portion of the cricoid cartilage. The mucous membrane in this commissure is very loosely attached to the deeper structures, and is thrown into folds by the approximation of the arytenoid cartilages. Its color is much lighter than that of the ary-epiglottic folds, due to the shining through of the cricoid cartilage. Outside of the ary-epiglottic folds and the inter-arytenoid commissure is the tissue forming the posterior and lateral walls of the oesophagus (not shown in the diagrams), and near the epiglottis a space called the pyriform sinus is noticed between the ary-epiglottic folds and the wall of the oesophagus.
Running from the epiglottis to the ary-epiglottic folds are two broad bands, one on either side, covered with mucous membrane and of a pinkish-red color, which are lost on either side in the tissue forming the walls of the laryngeal cavity, while toward the middle of the image they present concave and tolerably sharp edges. These are the ventricular bands, which were formerly termed the false vocal cords, and which form the lip to the opening of the ventricle of the larynx. Between the ventricular bands filling up the central portion of the image are seen the vocal cords, two bands of a pearl-white color which are attached to a cartilaginous process of the arytenoid cartilages, and run from these parallel with each other to the angle of the thyroid cartilage immediately below the tubercle of the epiglottis. These present sharp edges toward each other, and follow the motions of the arytenoid cartilages to which they are attached, so that when in inspiration the cartilages are separated the edges of the vocal cords are also some distance apart, forming, together with the inter-arytenoid commissure, a triangular opening called the glottis. That portion of the opening which is bounded on either side by the edges of the vocal cords alone is called the membranous portion, while the base of the triangle is termed the cartilaginous portion, being bounded on either side by the vocal processes of the arytenoid cartilages. This portion is readily distinguished from the membranous portion by its slightly yellow color, and by the fact that a very obtuse angle is formed at the junction of the two portions when the glottis is wide open during respiration. Through the open glottis the lower edge of the cricoid cartilage and several of the rings of the trachea can usually be seen, and there are a few cases in which even the bifurcation of the trachea can be dimly illuminated, showing in the laryngeal image the openings of the bronchi. The distance is, however, too great for bright illumination, and nothing can be seen distinctly, so that it is of little value in a diagnostic point of view. During phonation the glottis is narrowed to a slit by the approximation of the arytenoid cartilages and inner edges of the vocal cords, and, as has already been stated, the inter-arytenoid space becomes obliterated. In the higher notes of the female voice, the so-called head tones, the cartilaginous portion of the glottis remains closed entirely, while the membranous portion appears as an elliptical opening which is diminished in its longitudinal diameter with each rise in pitch. This becomes possible because of the presence in the vocal cords of a slender rod-like cartilage attached to the end of the vocal process, which can readily be seen in the female larynx, but which is only rudimentary in the male.