HYPOPHYSEAL MORPHOLOGY 



163 



It should be noted that Etkin's results do 

 not show that contact with neural tissue is 

 unnecessary for the initiation of the differ- 

 entiation of the adenohypophysis from its 

 epithelial anlage, because the buccal ecto- 

 derm is in contact with neural tissue before 

 the development of either Rathke's pouch 

 or the infundibulum. They do show, how- 

 ever, that the development of the adenohy- 

 pophysis can proceed without continued 

 contact with the neural element. 



According to Eakin and Bush (1957), the 

 pars nervosa develops without any consist- 

 ent departure from normality in frogs 

 (Hyla regilla) adenohypophysectomized at 

 the limb-bud stage. Regeneration of a pars 

 anterior often occurred giving albino tad- 

 poles which metamorphosed normally. In 

 one case a black nonmetamorphosing tad- 

 pole was found to have an adenohypophys- 

 eal fragment composed exclusively of cells 

 similar to those of the normal pars inter- 

 media. 



The first appearance of granulated cells 

 in the developing adenohypophysis presents 

 some features of endocrinologic interest. 

 Jost and Danysz (1952) found glycoprotein 

 granules in basophil cells in the rabbit fetus 

 after 20 days gestation. In the rat (Jost and 

 Tavernier, 1956) glycoprotein granules ap- 

 pear in the ventral portion of the pars an- 

 terior after 15 days and in the central por- 

 tion after 17 days gestation. In both species 

 the granules appear when the first evidence 

 for gonadotrophin and thyrotrophin is ob- 

 served. 



In the human fetus basophil cell granules 

 appear in the developing hypophysis much 

 earlier than acidophil cell granules. Baso- 

 phil cell granules are seen after 8 weeks ges- 

 tation, whereas the first definite acidophil 

 cell granules appear only at the 19- to 20- 

 week stage (Pearse, 1953; Romeis, 1940). 

 Romeis identified these early-appearing 

 basophil cells as /3-cells (purple ^-cells) in 

 the specific sense in which he uses this term. 

 Inasmuch as intermedin appears in the hu- 

 man fetal hypophysis about the same time 

 as these basophil cells (Keene and Hewer, 

 1924) , it is possible that the ^-cells of Ro- 

 meis in the human hypophysis are inter- 

 medin-secreting cells and correspond to the 

 cells of the pars intermedia of other mam- 

 mals. More convincing evidence in support 



of this hypothesis is presented in the section 

 on the human hypophysis. 



III. Anatomic Subdivisions of the 

 Hypophysis. Definition of Terms 



The hypophysis is very variable in form 

 in different vertebrates. Even among the 

 mammals there is considerable variation. 

 The comparative anatomy of the hypophy- 

 sis has been reviewed by Romeis (1940), 

 Green (1951), and Herlant (1954a). The 

 nomenclature is in a state of considerable 

 confusion and ill adapted to the needs of 

 the comparative morphologist. Confusion 

 arises from the great numbers of synonyms 

 in use, the use as synonyms of terms that 

 are not strictly synonymous, and the use of 

 the same term for structures that are not 

 strictly homologous. 



Because of the importance of a rigid and 

 consistent system of nomenclature, it seems 

 advisable for the purpose of this chapter to 

 adoi^t such a system and to use a single term 

 for each structure, avoiding all use of syn- 

 onyms except where it is necessary to quote 

 from, or to refer in specific terms to, the 

 publications of other authors. I shall make 

 no attempt to list the various synonyms or 

 near synonyms in use, or to eciuate my usage 

 with the varying usages which appear in 

 past and current literature. 



A. ANATOMIC DIVISIONS AND COMPONENTS 



The mammalian hypophysis (and that of 

 most terrestrial vertebrates) may be di- 

 vided into three parts (Fig. 3.1). (1) The 

 median eminence, forming the floor of the 

 third ventricle of the brain and contiguous 

 with the hypothalamus. (2) The hypophys- 

 eal stalk, an attenuated connection between 

 the other two divisions. (3) The lobular hy- 

 pophysis, an expanded structure enclosed in 

 the pituitary fossa, the latter being a cavity 

 or sac formed by dura and bone. 



Each division consists of an adenohypo- 

 physeal component derived by way of 

 Rathke's pouch from the buccal ectoderm 

 and a neurohypophyseal component derived 

 from the neural tissue in the floor of the 

 third ventricle. These components will be 

 named by the addition of prefixes to tlif 

 names characterizing the three division-, 

 thus: 



