Pituitary gland. Coloured Scanning Electron Micro- graph (SEM) of the pars intermedia region of the pituitary gland. The pituitary gland (hypophysis) is the master endocrine gland, located at the base of the skull. At centre is the pars intermedia or middle region of the gland which is lobular in structure, with rounded hormone-secreting cells and small hollow vessels. Melanocyte-stimulating hormone (MSH) is secreted here. At top left is the anterior region (adenohypophysis) of the gland; at lower right is the posterior region (neurohypophy- sis). Regions of the pituitary secrete different hormones. Magnification: x550 at 6x7cm size. x715 at 4x5"~LANDSCAPE"