80 THE TISSUES 



Cilia are confined to the surface cells of simple columnar and 

 stratified columnar epithelium. 



Simple columnar ciliated epithelium occurs in the smaller bronchi, 

 uterus, Fallopian tubes and central canal of the spinal cord. 



Stratified columnar ciliated epithelium occurs in large bronchi, 

 trachea, larynx, nose, Eustachian tube, vas deferens and epididymis. 



(b) Pigmented epithelmm consists of cells the cytoplasm of which 

 contains brown or black pigment (Fig. 27). It is usually present in 

 the form of spherical or rod-like granules. Examples of it are seen 



in the pigmented epithelium of the 



^zb^ -<-, ■>'^'?^% i-«^ ^ retina and in the pigmented cells 

 !^!.^^;;^;..^?L>^:^'??f«^i^ ^f ^-^^ ^^^p^^ l^^^^g of ^.^g epi- 

 dermis in colored races. 



(c) Glandular Epithelium. — 

 This forms the essential or secret- 

 ing element of glands and is mostly 

 of the simple cylindrical variety, 

 frequently modified to conical to 

 conform to their concentric ar- 



Fig 2 7.-Pigmented Epithelial Cells ^angement with reference to the 



Irom the Human Retina (X350), show- » 



ing different degrees of pigmentation. gland lumen. The general fea- 



The clear spots in the centres of the cells , ^ , , , • . i 1 • 



represent the unstained nuclei. tures of glandular epithelium are 



described on p. 217. The dift"erent 



kinds of glands and their epithelia are described among the organs. 



(d) N euro-epithelium. — This is a highly specialized form of epithe- 



Hum which occurs in connection with the end organs of nerves, under 



which heading it will be described. 



Mesothelium and Endothelitim 



While recognizing the present tendency toward considering those 

 tissues formerly classified as endothelium, as simple squamous epithe- 

 lium, the correctness of the newer classification still remains sub 

 iudice and, so long as this is the case, we prefer to retain the certainly 

 much more convenient classification of Minot, which coincides with 

 his subdivision of the mesoblast. According to this classification for 

 those tissues which resemble epithelium in structure and which are 

 derived from the sublayer of the mesoderm which he designates the 

 mesenchyme, the term endothelium is retained. The term mesothe- 

 lium is used for those tissues which resemble epithelium but are de- 



