PITUITARY liODV 413 



The Pituitary Body 



The PitiiiUiiy Eod} or Hypophysis Cerebri consists of two main 

 lobes which are totally different both in structure and in origin. 

 They are separated by a cleft, the interglandular cleft, and a narrow 

 strip of the posterior lobe bordering the cleft presents a different struc- 

 ture from other parts of the gland. This has been designated the 

 pars intermedia (Fig. 292). 



The Anterior Lobe {pars anterior). — This is the larger of the two 

 lobes and is distinctly glandular in character. It is of ectodermic 

 origin, developing as a diverticulum from the primitive oral cavity. 

 Its mode of development is that of a compound tubular gland, the 

 single primary diverticulum undergoing repeated division to form 

 the terminal tubules. The original diverticulum ultimately atrophies 

 and disappears, leaving the gland entirely unconnected with the sur- 

 face. The gland is enclosed in a connective-tissue capsule from 

 which trabeculae pass into the organ forming its framework. The 

 gland cells are arranged in slightly convoluted tubules and rest upon a 

 basement membrane. Between the tubules is a vascular connective 

 tissue. Some of the gland cells are small cuboidal cells with nuclei at 

 their bases and a clear or finely granular cytoplasm {chief cells). 

 Others, somewhat less numerous than the preceding, are larger and 

 polygonal with centrally placed nuclei, and cytoplasm containing 

 coarse basophile granules {chromophile cells). Cells with distinctly 

 eosinophile granules may also be present. There has been much 

 controversy as to whether these cells are fundamentally different or 

 merely represent different secretory conditions or stages. The large 

 variation in relative number of the different forms, and the occurrence 

 of cells which apparently represent intermediate stages, render it 

 probable that all should be considered as merely different functional 

 conditions of the one type of cell. 



As in all ductless glands, the blood supply is rich, the vessels being 

 sinusoidal in character, and the relations of capillaries to gland cells 

 is extremely intimate, dense networks of capillaries surrounding the 

 alveoli on all sides. In some places the cells are so placed around a 

 capillary as to resemble the relation of gland cells to the lumen. 



The Posterior Lobe {pars posterior, pars nervosa). — This like the 

 anterior lobe is surrounded by a connective- tissue capsule which 

 sends trabeculae into its substance. In the human adult the lobe 

 consists mainly of neuroglia with a few scattered" cells, which probably 



