CILIATED EPITHELIUM. 201 



Hum* cells are met with in their most characteristic form lining the mucous membrane 

 of the intestines. 



Some columnar epithelium-cells are very long, others very short, so as to look 

 cubical when seen in profile. They vary in form, moreover, according to the shape 

 of the surface which they cover, thus they may be larger at the base than at the 

 free end, as when they line a tube or duct, and in a section of this they then 

 appear wedge- shaped. 



Some epithelium cells, which must be reckoned in with this variety, have a peculiar 

 striated aspect in the basal or fixed half of the cell. This is the case with the cells 

 which line the smaller ducts of the salivary glands and some of the tubules of the 

 kidney (fig. 234 and fig. 235, d). 



In the human subject, columnar epithelium is chiefly, but by no means exclu- 

 sively, derived from the hypoblast. 



Glandular epithelium. This variety of epithelium is chiefly characteristic 

 of the terminal recesses or alveoli of secreting glands. In form the cells are 

 columnar, cubical, polyhedral or spheroidal, and are usually set round a tubular or 

 saccular cavity, into which the secretion is poured (fig. 235, a). The protoplasm 

 of the cells is generally occupied by the materials which the 

 gland secretes. This epithelium will be more fully described 

 in the chapter on secreting glands. 



Ciliated epithelium. In this form of epithelium, the 

 cells, which are generally columnar, bear at their free 



Fig. 236. COLUMNAR CILIATED EPITHELIUM CELLS FROM THE HUMAN 

 NASAL MEMBRANE; MAGNIFIED 300 DIAMETERS. (Sharpey. ) 



extremities little hair-like processes, which are agitated in- 

 cessantly during life, and for some time after systemic death, 

 with a lashing or vibrating motion. These minute and delicate moving organs 

 are named cilia. They exist very extensively throughout the animal kingdom ; 

 and the movements which they produce are subservient to very varied purposes in 

 the animal economy. 



Distribution and use. In the human body ciliated epithelium occurs in the 

 following parts, viz : 1. On the mucous membrane of the air-passages and its pro- 

 longations. It commences at a little distance within the nostrils, covers the mem- 

 brane of the nose (except the proper olfactory part) and of the adjoining bony sinuses, 

 and extends up into the nasal duct and lachrymal sac. From the nose it spreads 

 backwards a certain way on the upper surface of the soft palate, and over the upper 

 or nasal region of the pharynx ; thence along the Eustachian tube and lining 

 membrane of the tympanum, of which it covers the greater part. The lower part 

 of the pharynx is covered by scaly epithelium ; but the ciliated epithelium begins 

 again in the larynx a little above the glottis, and continues throughout the trachea 

 and the bronchial tubes in the lungs to their smallest ramifications. Over the vocal 

 cords, however, the epithelium is of the stratified scaly variety. 2. On the mucous 

 lining and in the glands of the body of the uterus and extending along the Fallopian 

 tubes, even to the peritoneal surface of the latter at their fimbriated extremities. 

 3. In the testicle lining the vasa efferentia, coni vasculosi, and first part of the tube 

 of the epididymis. 4. Lining the ventricles of the brain, except the fifth ventricle, 

 and throughout the central canal of the spinal cord. 5. In the excretory ducts of 

 certain small racemose glands of various parts (tongue, pharynx, &c.) 6. In the 

 embryo, lining the oesophagus and parts of the stomach and extending also over the 

 whole of the pharynx. 1 



1 Cilia have also been described in some mammals at the commencement of the tubules of the kidney 

 (Klein), a situation where in lower vertebrates they have long been known to exist. 



