THE EPITHELIAL TISSUES. 2 / 



Simple squamous epithelium occurs in but few places : 



Partially lining the tympanic cavity, including the mastoid 

 cells ; parts of the membranous labyrinth ; the infun- 

 dibula and alveoli of the lungs ; the posterior surface of 

 the anterior capsule of the crystalline lens; parts of 

 ducts of glands ; the capsule of the Malpighian body and 

 the descending limb of Henle's loop in the kidney; choroid 

 plexuses and parts of brain-ventricles. 



Stratified squamous epithelium occurs widely distributed, cover- 

 ing 



The_skin and its extensions, as the external auditory canal, 

 a5njtnrctival sac, and cornea ; the mouth, lower part of 

 pharynx, and oesophagus ; the epiglottis and upper part 

 of larynx, together with the false and true vocal cords ; 

 the pelvis of kidney, ureter, bladder, beginning and end 

 of male and entire female urethra; the vagina. 



Simple columnar epithelium occurs: 



a. Non-ciliated, in 



The digestive tract, from the cesophageal opening of stomach 

 to anus, as well as in the larger ducts of the glands com- 

 municating with this tube ; ducts of mammary glands ; 

 seminal vesicles and ejaculatory ducts ; membranous and 

 penile portions of urethra. 



b. Ciliated, in 



Oviduct, uterus, and part of canal of cervix ; greater part 

 of brain-ventricles and canal of spinal cord. 



Stratified columnar epithelium occurs : 



a. Non-ciliated, in- 



Terminal part of the vas deferens ; olfactory part of nasal 

 fossae. 



b. Ciliated, in 



The Eustachian tube and parts of tympanic cavity ; lachry- 

 mal passages ; respiratory part of nasal fossae, with com- 

 municating sinuses ; ventricle of larynx, trachea, and 

 bronchiae ; epididymis and first part of vas deferens. 



Squamous Epithelium. When occurring as a simple layer, 

 the flattened, polyhedral, nucleated plates form a regular mosaic ; 

 such epithelium is found but seldom in the human body, the lining of 

 the air-sacs of the lung, the posterior surface of the anterior capsule 

 of the crystalline lens, the membranous labyrinth, and a few other 

 localities being its principal seats. 



