1084 SPLANCHNOLOGY 



it is closely adherent, and forms the aryepiglottic folds which bound the entrance of the larynx. 

 It lines the whole of the cavity of the larynx; forms, by its reduplication, the chief part of the 

 ventricular fold, and, from the ventricle, is continued into the ventricular appendix. It is then 

 reflected over the vocal ligament, where it is thin, and very intimately adherent; covers the 

 inner surface of the conus elasticus and cricoid cartilage; and is ultimately continuous with the 

 lining membrane of the trachea. The anterior surface and the upper half of the posterior surface 

 of the epiglottis, the upper part of the aryepiglottic folds and the vocal folds are covered by 

 stratified squamous epithelium; all the rest of the laryngeal mucous membrane is covered by 

 columnar ciliated cells, but patches of stratified squamous epithelium are found in the mucous 

 membrane above the glottis. 



Glands. The mucous membrane of the larynx is furnished with numerous mucous secreting 

 glands, the orifices of which are found in nearly every part; they are very plentiful upon the 

 epiglottis, being lodged in little pits in its substance; they are also found in large numbers along 

 the margin of the aryepiglottic fold, in front of the arytenoid cartilages, where they are termed 

 the arytenoid glands. They exist also in large numbers in the ventricular appendages. None 

 are found on the free edges of the vocal folds. 



Vessels and Nerves. The chief arteries of the larynx are the laryngeal branches derived 

 from the superior and inferior thyroid. The veins accompany the arteries; those accompanying 

 the superior laryngeal artery join the superior thyroid vein which opens into the internal jugular 

 vein; while those accompanying the inferior laryngeal artery join the inferior thyroid vein 

 which opens into the innominate vein. The lymphatic vessels consist of two sets, superior 

 and inferior. The former accompany the superior laryngeal artery and pierce the hyothyroid 

 membrane, to end in the glands situated near the bifurcation of the common carotid artery. Of 

 the latter, some pass through the middle cricothyroid ligament and open into a gland lying in 

 front of that ligament or in front of the upper part of the trachea, while others pass to the deep 

 cervical glands and to the glands accompanying the inferior thyroid artery. The nerves are 

 derived from the internal and external branches of the superior laryngeal nerve, from the 

 recurrent nerve, and from the sympathetic. The internal laryngeal branch is almost entirely 

 sensory, but some motor filaments are said to be carried by it to the Arytaenoideus. It enters 

 the larynx by piercing the posterior part of the hyothyroid membrane above the superior 

 laryngeal vessels, and divides into a branch which is distributed to both surfaces of the epi- 

 glottis, a second to the aryepiglottic fold, and a third, the largest, which supplies the mucous 

 membrane over the back of the larynx and communicates with the recurrent nerve. The external 

 laryngeal branch supplies the Cricothyreoideus. The recurrent nerve passes upward beneath 

 the lower border of the Constrictor pharyngis inferior immediately behind the cricothyroid joint. 

 It supplies all the muscles of the larynx except the Cricothyreoideus, and perhaps a part of the 

 Arytsenoideus. The sensory branches of the laryngeal nerves form subepithelial plexuses, from 

 which fibers pass to end between the cells covering the mucous membrane. 



Over the posterior surface of the epiglottis, in the aryepiglottic folds, and less regularly in 

 some other parts, taste-buds, similar to those in the tongue, are found. 



THE TRACHEA AND BRONCHI (Fig. 961). 



The trachea or windpipe is a cartilaginous and membranous tube, extending 

 from the lower part of the larynx, on a level with the sixth cervical vertebra, to the 

 upper border of the fifth thoracic vertebra, where it divides into the two bronchi, 

 one for each lung. The trachea is nearly but not quite cylindrical, being flattened 

 posteriorly; it measures about 11 cm. in length; its diameter, from side to side, 

 is from 2 to 2.5 cm., being always greater in the male than in the female. In 

 the child the trachea is smaller, more deeply placed, and more movable than 

 in the adult. 



Relations. The anterior surface of the trachea is convex, and covered, in the neck, from 

 above downward, by the isthmus of the thyroid gland, the inferior thyroid veins, the arteria 

 thyroidea ima (when that vessel exists), the Sternothyreoideus and Stern ohyoideus muscles, 

 the cervical fascia, and, more superficially, by the anastomosing branches between the anterior 

 jugular veins; in the thorax, it is covered from before backward by the manubrium sterni, 

 the remains of the thymus, the left innominate vein, the aortic arch, the innominate and left 

 common carotid arteries, and the deep cardiac plexus. Posteriorly it is in contact with the 

 esophagus. Laterally, in the neck, it is in relation with the common carotid arteries, the right 

 and left lobes of the thyroid gland, the inferior thyroid arteries, and the recurrent nerves; in 

 the thorax, it lies in the superior mediastinum, and is in relation on the right side with the 

 pleura and right vagus, and near the root of the neck with the innominate artery; on its left side 

 are the left recurrent nerve, the aortic arch, and the left common carotid and subclavian arteries. 



