60 



STUDENTS HISTOLOGY 



FIG. 35. GLANDULAK EPITHELIUM. 



A. A. Polyhedral cells from human liver. 



B. Double nuclei. 



C. Cells from same showing connection with a capillary. 



D. Same cells infiltrated with globules of fat. 



E. Cells from liver of pig showing intracellular network (X 400). 



pigment -granules and the fat -globules in the body of the cells. 

 Masses of these cells resemble somewhat pavement epithelium ; they 

 are not flat, but polyhedral. 



ENDOTHELIUM 



Endothelium resembles simple squamous epithelium in appear- 

 ance, and it is called epithelium by some histologists. 



Endothelium forms the superficial covering of the pleural, peri- 

 cardial, and peritoneal cavities, the tunica vaginalis, and the joints. 

 It covers the membranes of the brain and spinal cord, the inner 

 surfaces of the heart, and the blood- and lymphatic vessels. 

 Therefore endothelium lines the cavities that do not communicate 

 with the external world. * 



It consists of a single layer of thin, flat cells, held together by a 

 small amount of intercellular substance. It is demonstrated best 

 on fresh tissues, hence the human subject is seldom available. 



The mesentery of the frog affords a good example of endothelial 



*Remember that the peritoneum may be said to have an opening by way of the Fallopian 

 tube, and that the central canal of the spinal cord and brain is lined by epithelium but has no 

 opening that connects it with the external world. 



