Pituitary gland (Latin)

The adenohypophysis is derived from an outpouching of the paries superior cavitas oris and is comprised of three parts: the pars distalis, pars tuberalis, and pars intermedia. The pars distalis is the largest part and is responsible for most of the secretory activity. The pars tuberalis is a posterior extension of the lobus anterior that surrounds the truncus infundibularis, while the pars intermedia is located between the pars distalis of the adenohypophysis and the neurohypophysis. A small cleft is generally apparent between the pars distalis and intermedia. The neurohypophysis is a diencephalic structure and is essentially an extension of the hypothalamus. It can be divided into two main parts. The superior portion is continuous with the eminentia mediana hypothalami and is known as the truncus infundibularis. It is comprised of thousands of unmyelinated hypothalamohypophyseal axons. The lower, larger portion of the neurohypophysis belongs to the pars nervosa; it mainly consists of the terminal endings of hypothalamohypophyseal neurons.