Surgical Anatomy

The adrenal glands were first described in 1552 by the Italian anatomist Bartolomeo Eustachi in his Opuscula Anatomica as ‘‘glandulae renis incumbentes’’ (glands lying on the kidney) [1], but their function remained controversial for the next 300 years [2]. The adrenal have a dual origin (Fig. 2.1a, b), i.e. the cortex arises from mesoderm whereas the medulla has a neuroectodermal origin [2]. The cortex develops during the second month of gestation as a proliferation of coelomic mesothelium into the underlying mesenchyme between the root of the dorsal mesogastrium (the root of the mesentery) and the urogenital ridge (the mesonephros and the developing gonad). Here, these cellular proliferations differentiate into large acidophilic organs that form the fetal or primitive cortex of the adrenal gland [3]. The proliferating tissue extends from the level of the sixth to the 12th thoracic segments and becomes larger than the kidney at midgestation [4]. Shortly afterward, a second wave of cells from the mesothelium penetrates the mesenchyme and surrounds the original acidophilic cell mass; these cells, smaller than those of the first wave, later form the definitive cortex of the gland. The fetal cortex undergoes rapid degeneration during the first 2 weeks after birth, accounts for only one quarter of the cortical at age of 2 months, and has vanished by 1 year. When the proliferation of the coelomic epithelium ceases, the cortex becomes enveloped by a mesodermal capsule, probably derived from the mesonephros.