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VETEEINAEY PHYSIOLOGY 



modified cells, chalice cells, are always found. They are 

 larger than the columnar cells, and somewhat pear-shaped, 

 being attached by their small extremity. Their protoplasm 

 is collected at their point of attachment, while the body of 

 the cell is filled with mucin, a clear, transparent material. 



3. Secreting Epithelium. A number of cells, having for 

 their function the production of some material which is to be 

 excreted from the cell, are arranged as the lining of depres- 

 sions, the glands. 



The simplest form of gland is the simple tubular a test- 

 tube-like depression, lined by secreting cells. Instead of 

 being simple, the tube may be branched, when the gland is 

 said to be racemose. .In many glands the secreting epi- 



FIG. 5. (a) Columnar Epithelium from the small intestine ; (b) Ciliated 

 Epithelium from the trachea. 



thelium is confined to the deeper part of the tube, the 

 alveolus or acinus (fig. 6), while the more superficial part 

 is lined by cells which do not secrete, forming the duct. 



In many situations several simple glands are grouped 

 together, their ducts opening into one common duct, and 

 a compound gland results. 



Secreting epithelium varies according to the material it 

 produces. 



(A) Muein-seereting Epithelium. Many glands have for 

 their function the production of mucus, a slimy substance 

 of use in lubricating the mouth, stomach, intestine, etc. 

 The acini containing such cells are usually large. The cells 

 themselves are large, and are placed on a delicate basement 

 membrane, a condensation of the subjacent fibrous tissue, 

 which bounds the acinus. The nuclei are situated near 



