ABSTRACT
While it is recognized that the full gestation period of the mouse is substantially shorter than that of the human, the early development of the mouse has probably been studied in considerably greater detail than comparable events in the latter species. This is principally because of the wider accessibility of both pre-and early post-implantation stages of mouse embryonic development and the relative ease to which it has been possible to undertake experimental studies using both intact embryos and more recently genetically manipulated cell lines that are derived from them. While it was formerly technically possible to observe the development of the pre-and early post-implantation stages of mouse development only in tissue culture, this is now no longer the case. The availability of pluripotent cell lines established from the inner cell mass region of blastocysts and, more recently, from primordial germ cells, has allowed the development in tissue culture of a very wide range of cell types. These pluripotent cell lines have provided an essential step toward development of technologies allowing specific modification of mouse genes and led to the 2007 Nobel Prize in Physiology or Medicine. These approaches led to rapid progress in creation of genetically engineered mouse (GEM) models that now allow for the analysis of normal and an increasingly wide range of diseases. Despite the enormous advances in this area, it is still essential to understand the early events that are associated with the normal development of the various endocrine glands in the mouse. During the early stages of their development, all of the endocrine organs appear to form without any obvious common features. It is only later, once a reasonable state of differentiation has been achieved, that it is possible to recognize that they, in fact, appear to share certain common features. All appear to be associated with a well-developed vascular system, and this is later seen to be of critical importance in facilitating their homeostatic role in the adult. With regard to the pineal gland, in particular, this possesses complex neural connections with the retina and, some authorities believe, additionally to a wide range of other structures.
