THE TRACHEA 523 
ordinary breathing the rima is somewhat lanceolate in form (Fig. 465); when dilated, 
it is diamond-shaped, the widest part being between the vocal processes. The 
narrow part of the glottis between the vocal cords is termed the glottis vocalis (Pars 
intermembranacea), while the wider part between the arytenoid cartilages is the 
glottis respiratoria (Pars intercartilaginea). 
In the revised nomenclature the terms “true’’ and “‘false’’ vocal cords have been replaced 
by “labium vocale” and “‘plica ventricularis.”” The labium vocale consists of the plica vocalis, 
lig. vocale, and m. vocalis; the last forms the bulk of the projection. 
The posterior compartment of the laryngeal cavity is directly continuous with 
the trachea. It is enclosed by the cricoid cartilage and the crico-thyroid membrane. 
It is clearly marked off laterally by the vocal cord and the projection caused by the 
posterior border of the arytenoid cartilage. It is oval in form, the transverse 
diameter being an inch and a half to two inches (ca. 4 to 5 em.), and the dorso- 
ventral diameter two to two and a half inches (ca. 5 to 6 cm.). 
The mucous membrane of the larynx (Tunica mucosa laryngis) is reflected 
around the margin of the aditus to become continuous with that of the pharynx, 
and is continuous behind with that which lines the trachea. It is closely attached 
to the epiglottis, except at the base, but elsewhere in the aditus and vestibule it is 
loosely attached by submucous tissue which contains many elastic fibers. It is 
thin and very closely adherent over the vocal cords and the medial surfaces of the 
arytenoid cartilages. The epithelium is of the stratified squamous type from the 
aditus to the glottis, beyond which it is columnar ciliated in character. There are 
numerous mucous laryngeal glands (Glandule laryngex), except in the glottis and 
the pharyngeal surface of the epiglottis, in which situations they are scanty. Lymph 
nodules (Noduli lymphatici laryngei) are also present, especially at the lateral 
ventricle. 
Vessels and Nerves.—The arteries are derived from the laryngeal and ascend- 
ing pharyngeal arteries. The veins correspond to the arteries. The lymph- 
vessels go to the anterior cervical and pharyngeal lymph glands. The nerves 
come from the vagus. The recurrent or posterior laryngeal is the motor nerve to 
the muscles with the exception of the crico-thyroideus. The anterior laryngeal 
is the sensory nerve; it commonly supplies the nerve to the crico-thyroideus. 
THE TRACHEA 
The trachea extends from the larynx to the roots of the lungs, where it divides 
into the right and left bronchi. It is kept permanently open by a series of fifty to 
sixty incomplete cartilaginous rings embedded in its wall. It occupies a median 
position, except near its termination, where it is pushed a little to the right by the 
arch of the aorta. It is approximately cylindrical, but its cervical part is for the 
most part depressed dorso-ventrally by contact with the longus colli muscle, so 
that the dorsal surface is flattened. Its average length is about 30 to 32 inches (ca. 
75 to80em.). The average caliber is about two to two and one-half inches (ea. 5 to 
6 cm.), but in the greater part of the neck the transverse diameter is greater and the 
dorso-ventral smaller.! It is enclosed by a fascia propria. 
In its cervical part (Pars cervicalis) the trachea is related dorsally to the 
csophagus for a short distance, but chiefly to the longus colli muscles. It is related 
laterally to the lateral lobes of the thyroid gland, the carotid artery, the jugular 
vein, the vagus, sympathetic, and recurrent laryngeal nerves, and the tracheal 
1 At its origin the trachea is almost circular in cross-section and the average diameter is 
about two and a quarter inches (ca. 5.5 cm.). It soon becomes flattened dorso-ventrally, so that 
the transverse diameter may be nearly three inches (ca. 7 cm.) and the dorso-ventral about two 
inches (ca. 5 cm.). In the thorax the diameters become more nearly equal, and sometimes the 
dorso-ventral diameter is the greater; this is the case where the aorta crosses the trachea. 
