CHAPTER VIII 



SPECIAL MEMBRANES AND GLANDS 

 MEMBRANE 



The word " membrane " in its widest sense is used to designate 

 any thin expansion of tissue. Thus we speak of the periosteum 

 as a fibrous membrane ; and the layer of cells beneath the epi- 

 thelium of free surfaces is called a basement membrane. In a 

 restricted, although the commonest sense, the word " membrane " 

 is used to denote an enveloping or a lining tissue of the body. 



Classification of membranes. — The chief membranes of the 

 body are classified as follows : — 



1. Serous. 



2. Synovial. 



3. Mucous. 



4. Cutaneous. 



SEROUS MEMBRANES 



Serous membranes are thin, transparent, tolerably strong, and 

 elastic. The surfaces are moistened by a fluid resembling serum, 

 from which the membranes obtain their name of serous mem- 

 branes. They consist of two layers only: (1) endothelium, 

 (2) corium. 



(1) Endothelium is the name given to a variety of epithelium 

 found lining {i.e. lying within) certain parts of the body. It 

 consists of a single layer of flattened transparent cells joined 

 edge to edge so as to form a smooth membrane. 



(2) The corium consists of a thin layer of fibrous tissue, and con- 

 tains blood-vessels, lymph-vessels, and lymphoid tissue. 



Serous membranes are attached to the underlying parts by 

 areolar tissue, called " subserous " tissue. They are found lining 

 closed cavities and passages that do not communicate with the 

 exterior. They may be divided into three classes : — 



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