THE LARYNX1
The Larynx is the organ of voice, placed at the upper part of the air passage. It is situated between the trachea and base of the tongue, at the upper and fore part of the neck, where it forms a considerable projection in the middle line. On either side of it lie the great vessels of the neck; behind, it forms part of the boundary of the pharynx, and is covered by the mucous membrane lining this cavity.
The larynx is narrow and cylindrical below, but broad above, where it presents the form of a triangular box, being flattened behind and at the sides, whilst in front it is bounded by a prominent vertical ridge. It is composed of cartilages, connected together by ligaments, moved by numerous muscles, lined by mucous membrane, and supplied with vessels and nerves.
The cartilages of the larynx are nine in number, three single and three pairs:
The Thyroid is the largest cartilage of the larynx. It consists of two lateral lamellae or alae, united at an acute angle in tront, terming a vertical projection in the middle line, which is prominent above, and called the
pomum Adami. This projection is subcutaneous, more distinct in the male than in the female, and occasionally separated from the integument by a bursa mucosa.
Each lamella is quadrilateral in form. Its outer surface presents an oblique ridge, which passes downwards and forwards from a tubercle, situated near the root of the superior cornu. This ridge gives attachment to the Sterno-thyroid and Thyro-hyoid muscles; the portion of cartilage included between it and the posterior border, to part of the Inferior constrictor muscle.
The inner surface of each ala is smooth, concave, and covered by mucous membrane above and behind; but in front, in the receding angle formed by their junction, is attached the epiglottis, the true and false chorda; vocales, the Thyro-arytenoid, and Thyro-epiglottidean muscles.
The upper border of the thyroid cartilage is deeply notched in the middle line, immediately above the pomum Adami, whilst, on either side it is slightly concave. This border gives attachment throughout its whole extent to the thyro-hyoid membrane.
The lower border is connected to the cricoid cartilage, in the median line by the crico-thyroid membrane, and on each side by the Crico-thyroid muscle.
The posterior borders, thick and rounded, terminate above in the superior cornua, and below in the inferior cornua. The two superior cornua are long and narrow, directed backwards, upwards, and inwards, and terminate in a conical extremity, which gives attachment to the thyro-hyoid ligament. The two inferior cornua are shorter and thicker; they pass forwards and inwards, and present, on their inner surfaces, a small oval articular facet for articulation with the side of the cricoid cartilage. The posterior border receives the insertion of the Stylo-pharyngeus and Palato-pharyngeus muscles on each side.
The Cricoid Cartilage is so called from its resemblance to a signet ring . It is smaller but thicker and stronger than the thyroid cartilage, and forms the lower and back part of the cavity of the larynx.
Its anterior half is narrow, convex, affording attachment in front and at the sides to the Crico-thyroid muscles, and behind those to part of the Inferior constrictor.
Its posterior half is very broad, both from side to side and from above downwards; it presents in the middle line a vertical ridge for the attachment of the longitudinal fibres of the oesophagus; and on either side of this is a broad depression for the Crico-arytenoideus posticus muscle.
