298 HISTOLOGY 



LARYNX. 



The mucous membrane of the larynx is a continuation of that of the 

 pharynx, and accordingly consists of epithelium and tunica propria. A 

 submucosa connects it with the underlying parts. In most places the 

 epithelium appears to be stratified and columnar, but it is said to be 

 pseudo-stratified, with nuclei at several levels (Fig. 38, p. 49). It is 

 difficult to determine whether or not all the cells are in contact with the 

 basement membrane. This type of epithelium, which occurs also in the 

 trachea, is ciliated. The stroke of the cilia is toward the pharynx. A 

 stratified epithelium with squamous, non-ciliated outer cells is found on 

 the vocal folds (true vocal cords) , on the anterior surface of the arytaenoid 

 cartilages and on the laryngeal surface of the epiglottis. The distribution 

 of the two sorts of epithelium above the vocal folds is subject to individual 

 variation. The squamous epithelium often occurs in islands. The tunica 

 propria is composed of fibrous connective tissue with many elastic fibers, 

 and beneath the epithelium it forms a basement membrane (membrana 

 propria). It includes reticular tissue containing a variable number of 

 lymphocytes, which are gathered in solitary nodules in the wall of the 

 laryngeal ventricle (sinus of Morgagni). Connective tissue papillae are 

 found chiefly beneath the squamous epithelium. At the free border of the 

 vocal folds and on their under surface, the papillae unite to form longitud- 

 inal ridges. On the laryngeal surface of the epiglottis there are only 

 isolated papillae, against which rest the short taste buds. 



The submucosa contains mixed, branched, tubulo-alveolar glands, 

 measuring from 0.2 to i.o mm.; they are abundant in the ventricular 

 folds but are absent from the middle part of the vocal folds. The 

 ventricular folds (false vocal cords) consist of a loose vascular fatty tissue, 

 often containing small bits of elastic cartilage about i mm. long, and 

 similar cartilages measuring 2-3.5 mm. are sometimes found in the anterior 

 ends of the vocal folds. 



The cartilages of the larynx are mostly of the hyaline variety, resem- 

 bling those of the ribs. To this class belong the thyreoid, cricoid, the 

 greater part of the arytaenoid, and often the small triticeous cartilages. 

 Elastic cartilage is found in the epiglottis, the cuneiform and corniculate 

 cartilages, the apex and vocal process of the arytaenoids, and generally the 

 median part of the thyreoid. In women this portion is not involved in 

 the ossification (chiefly endochondral) which begins hi the thyreoid and 

 cricoid cartilages between the twentieth and thirtieth years. The tri- 

 ticeous cartilages (nodules in the lateral hyothyreoid ligaments, named 

 from their resemblance to grains of wheat) are sometimes composed of 

 fibro-cartilage. 

 The blood vessels form two or three networks parallel with the surface. 



