. The endocrine organs; an introduction to the study of internal secretion . n the form of a blind canal far into the parsnervosa, but in man this canal has become obliterated, although it existedin the early embryo. In front of and partly surrounding the pars nervosa the organ is formedof a mass of epithelium cells, granular in appearance. This constitutes thepars anterior seu glandularis. It is highly vascular. In the middle ofthe organ the pars anterior is separated from the pars nervosa by a cleftlined by columnar, cubical, or flattened epithelial cells and filled with glairy 74 Structure
. The endocrine organs; an introduction to the study of internal secretion . n the form of a blind canal far into the parsnervosa, but in man this canal has become obliterated, although it existedin the early embryo. In front of and partly surrounding the pars nervosa the organ is formedof a mass of epithelium cells, granular in appearance. This constitutes thepars anterior seu glandularis. It is highly vascular. In the middle ofthe organ the pars anterior is separated from the pars nervosa by a cleftlined by columnar, cubical, or flattened epithelial cells and filled with glairy 74 Structure of the Pituitary 75 fluid. In the adult human subject the cleft is generally found to beobliterated or broken up into isolated cysts containing a colloid-likematerial. The cleft is all that remains of the original tubular structureof the pars glandularis, which in the early embryo was formed by a pouch-like outgrowth of the buccal ectoderm (Rathkes pouch) communicating atfirst with the cavity of the mouth, although ultimately the communicationhas become obliterated. c d h. FIG. 45. — Mesial sagittal section through the pituitary body of an adult monkey (semi-diagrammatic). (Herring.) a, optic ehiasma; b, third ventricle (infundibulum); c, d, extension of pars intermedia round neck of pituitary ;e, pars anterior seu glandularis ; /, intraglandular cleft; g, pars intermedia ; h, pars nervosa. Traces of the original connexion with the buccal ectoderm may persist inexceptional cases even in the adult, as the so-called pharyngeal vestigial structure—the paraliypopliysis—has been described asoccurring in the dura mater lining of the sella turcica, and other smallaccessory bodies similar in structure to the anterior lobe have also beendescribed. It is possible that these may undergo hypertrophy after extirpa-tion of the main gland and partly supply its function. But the pars nervosa does not actually abut against the intraglandular 76 The Endocrine Organs
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