CHAPTER XI 

 THE PITUITARY BODY (HYPOPHYSIS CEREBRI) 



The next of the endocrine glands to claim our attention is the pituitary 

 body. The study of this organ has sprung into prominence within quite 

 recent years. Although somewhat vaguely connected with growth pheno- 

 mena, and shown (1887) to be related to certain forms of abnormal de- 

 velopment of the body, and especially of the skeleton, it was not until 1895 

 that it was suspected of having an active function : by most it was 

 regarded as a rudimentary structure having some morphological interest 

 but little or no physiological importance. Now, on the contrary, it is 

 known that from one part of the gland autacoid principles can be extracted 

 which exert an active influence upon some of the most essential organs of 

 the body ; whilst from another part it seems probable that principles are 

 furnished to the blood which serve as chemical regulators of nutrition and 

 growth. Moreover, by most of those who have worked at its functions 

 it is thought to be essential to life. Like most of the other special 

 endocrine organs it is found, with very few exceptions, throughout 

 the whole series of Vertebrata, and these exceptions may ultimately prove 

 only apparent. 



Structure of the Pituitary 



The pituitary body is in man a small organ about the size of a hazel- 

 nut without the shell, weighing a little more than half a gramme. It lies 

 at the base of the brain in the sella turcica of the sphenoid bone. It is 

 connected with the floor of the third ventricle by a short, hollow, funnel- 

 shaped stalk — the infundibulum. This stalk is composed of nervous 

 tissue, and expands in the interior of the gland into what is known as 

 the nervous portion — pars nervosa — which when examined by appropriate 

 methods is found to be mainly composed of neuroglia fibres and cells 

 (Herring). In some animals the cavity of the infundibulum with its lining 

 of ependyma is prolonged in the form of a blind canal far into the pars 

 nervosa, but in man this canal has become obliterated, although it existed 

 in the early embryo. 



In front of and partly surrounding the pars nervosa the organ is formed 

 of a mass of epithelium cells, granular in appearance. This constitutes the 

 pars anterior seu glandularis. It is highly vascular. In the middle of 

 the organ the pars anterior is separated from the pars nervosa by a cleft 

 lined by columnar, cubical, or flattened epithelial cells and filled with glairy 



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