TABLE Staining Characteristics of Cells Found in the Anterior Lobe of the Pituitary Gland 21.2 Cell Type Percentage of Total Cells General Staining Specific Staining Product Somatotrope (GH cell) 50 Acidophil Orange G (PAS ) Growth hormone (GH) Lactotrope (PRL cell) 15–20 Acidophil Orange G (PAS ) Herlant’s erythrosin Brooke’s carmosine Prolactin (PRL) Corticotrope (ACTH cell) 15–20 Basophil Lead hematoxylin (PAS  ) Proopiomelanocortin (POMC), which is cleaved in human into adrenocorticotropic hormone (ACTH) and -lipotrophic hormone (-LPH) Gonadotrope (FSH and LH cells) 10 Basophil Aldehyde-fuchsin Aldehyde-thionine (PAS  ) Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) Thyrotrope (TSH cell) 5 Basophil Aldehyde-fuchsin Aldehyde-thionine (PAS  ) Thyrotropic hormone (TSH)
Pars Tuberalis. The pars tuberalis is an extension of the anterior lobe along the stalklike infundibulum. It is a highly vascular region containing veins of the hypothalamohypophyseal system. The parenchymal cells are arranged in small clusters or cords in association with the blood vessels. Nests of squamous cells and small follicles lined with cuboidal cells are scattered in this region. These cells often show immunoreactivity for ACTH, FSH, and LH.
Posterior Lobe of the Pituitary Gland (Neurohypophysis)
The posterior lobe of the pituitary gland is an extension of the central nervous system (CNS) that stores and releases secretory products from the hypothalamus.
The posterior lobe of the pituitary gland, also known as the neurohypophysis, consists of the pars nervosa and the infundibulum that connects it to the hypothalamus.
TABLE Electron Microscopic Characteristics of Cells Found in the Anterior Lobe of the Pituitary Gland21.3 Cell Type Size/Shape Nucleus/Location Secretory Vesicle Size/ Characteristics Other Cytoplasmic Characteristics Somatotrope Medium/oval Round/central, with prominent nucleoli Dense: 350 nm, closely packed None Lactotrope Large/polygonal Oval/central Inactive: 200 nm, sparse Active: dense, pleomorphic, 600 nm, sparse Lysosomes increase after lactation Corticotrope Medium/polygonal Round/eccentric 100–300 nm Lipid droplets, large lysosomes, perinu-clear bundles of intermediate filaments Gonadotrope Small/oval Round/eccentric Dense: 200–250 nm Prominent Golgi apparatus, distended rER cisternae Thyrotrope Large/polygonal Round/eccentric Dense: 150 nm Prominent Golgi apparatus with numerous vesicles
FIGURE 21.8 • Photomicrograph of the pars intermedia of an adult human pituitary gland. This photomicrograph of a toluidine blue–stained specimen shows the pars intermedia located between the pars distalis (on the left) and pars nervosa (on the right). In humans, this portion of the gland is somewhat rudimentary. However, a characteristic feature of the pars intermedia is the presence of different-sized follicles filled with colloid (CF ) and small groups of cells consisting of chromophobes and basophils. 120.