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Comparative Cytology of the Neuro‐Intermediate Lobe of the Reptilian Pituitary
Author(s) -
Weatherhead Brian
Publication year - 1978
Publication title -
anatomia, histologia, embryologia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.34
H-Index - 35
eISSN - 1439-0264
pISSN - 0340-2096
DOI - 10.1111/j.1439-0264.1978.tb00661.x
Subject(s) - pars intermedia , median eminence , biology , anatomy , nerve cells , neuroscience , lobe , hypothalamus , cytology , pituitary gland , microbiology and biotechnology , endocrinology , genetics , hormone
Summary In many reptiles the pars nervosa bears a striking resemblance to the mammalian median eminence. The structure of the ependymal cells lining the infundibular recess and the fact that many of them are in synaptic contact with nerve fibres suggests that they subserve more than a mere structural role and that they may be involed in secretory or transport functions forming functional units with neuronal elements of the hypothalamus. All species possess large numbers of typical peptidergic fibres although some have in addition a second, rarer type; aminergic fibres are also present but their numbers vary in different species. The pars intermedia contains nerve fibres only in snakes and Caiman but even in these species the innervation is sparse. This observation coupled with the organisation of the pars nervosa leads to the conclusion that the latter may act, in part at least, as the “median eminence” of the pars intermedia. A more extensive survey, particularly amongst the families of lizards thought to be related to the ancestors of snakes, might throw further light upon the course of evolution of control mechanisms within the pars intermedia of reptiles.