Pituitary Anatomy and Development

Abstract

Although descriptions of the pituitary gland can be traced to the second century A.D., major advances continue to be made with respect to elucidating the organization and functional anatomy of this organ system. On the surface, the pituitary gland would appear to be a rather simple structure, containing two lobes (anterior and posterior) that are well visualized by MRI imaging, and gives rise to secreted hormones involved in the regulation of peripheral, target organs. However, the development, organization, and inner workings of the pituitary are vastly complicated. The anterior pituitary is comprised of three subdivisions including the pars distalis, pars intermedia, and pars tuberalis, all derived from Rathke’s pouch, but only the function of the pars distalis is well understood in man. Included among the complexity of pituitary anatomy is an expanding list of factors involved in the development of the anterior pituitary, a somewhat distinct topography for most the classic cell types in the pars distalis, morphological and physiological evidence for heterogeneity among these cells, evidence for cell clustering that may be involved in amplifying signals from the hypothalamus, local regulatory control mechanisms mediated by paracrine and autocrine secretion and modulation by glial-derived cell types, and the presence of stem cells that may be involved in postnatal plasticity of the anterior pituitary.