HISTOLOGY 



127 



secretion (Fig. 59). They are separated from the surrounding tissue by thin 

 membranes. The cells of the islands are round, cuboidal or polyhedral in 

 shape and form irregular cords. The round nuclei stain faintly. By special 

 staining methods the presence of cytoplasmic granules can be demonstrated 

 in the cells, showing differences in their staining reaction. Between the 

 cords of cells, capillaries provide an intimate blood supply. 



Pancreatic acinus 



Blood vessel 



Duct 



Pancreatic island 



Fig. 59. — Pancreas with pancreatic island. 



Respiratory System 



(X200.) 



The larynx. — The larynx connects the pharynx with the trachea. Its 

 walls contain cartilages covered by mucous membrane. The cartilages of 

 the larynx are mostly hyaline; only in the epiglottis and in the vocal process 

 of the arythenoid are elastic fibers present in the hyaHne ground substance. 

 The entrance of the larynx is guarded by the epiglottis which is attached 

 by a stalk antero-ventrally to the thyroid cartilage. The lingual and the 

 upper part of the laryngeal surface of the epiglottis and the aryo-epiglottic 

 folds of the larynx are covered by stratified squamous epithelium. At the 

 base of the epiglottis the epithelium changes from a stratified squamous type 

 into a pseudostratified ciliated columnar type which extends over the entire 

 surface of the larv'nx, except the true vocal cords. 



The lamina propria of the epiglottis is continuous with and firmly 

 attached to the perichondrium. The mucous membrane is rich in glands. 



