The pituitary gland, or hypophysis is a small gland which lies below the brain in a small cavity on the sella turcica.

The pituitary actually consists of two glands —the posterior neurohypophysis and the anterior adenohypophysis which are united anatomically. 

“Adeno” means “related to glands” and the adenohypophysis consists primarily of glandular epithelial tissue.

In comparison, the neurohypophysis consists mainly of neural secretory tissue, since the neurohypophysis arises from a bud of nervous tissue that grows down from the hypothalamus.

In between the anterior pituitary and posterior pituitary, is a thin strip of cystic tissue, called the pars intermedia, which is part of the anterior pituitary because the cysts are actually remnants of Rathke’s pouch, which is the embryological structure that eventually develops into the anterior pituitary.

Let’s move anteriorly and take a closer look at the adenohypophysis.
There are two main groups of cells that are named based on how well they stain. They are chromophils and chromophobes.

The chromophils have cytoplasm that stains strongly and as a result, appears darker; and chromophobes have cytoplasm that stains weakly and appear lighter in the image.

Chromophils are secretory cells in which hormone is stored in cytoplasmic granules. They are also called basophils and acidophils, based on their affinities for basic and acidic dyes, respectively. 

Acidophlis stain orange to red with acidic dyes. And acidophils consist of somatotrophs and lactotrophs. Somatotrophs secrete somatotropin or growth hormone thus, they are stimulated by growth hormone releasing hormone, and they are inhibited by somatostatin. 

Lactotrophs , the other variety of acidophils, produce and release prolactin which promotes mammary gland development during pregnancy as well as lactation after birth. 

The basophilic cells are the corticotrophs, gonadotrophs, and thyrotrophs. Basophils stain blue with basic dyes. And they secrete the remaining hormones associated with the anterior pituitary, including: Adrenocorticotrophic hormone or ACTH, Luteinising hormone or LH, Follicle stimulating hormone or FSH, and Thyroid stimulating hormone or TSH.

Let’s move onto the posterior pituitary, posterior pituitary contains non myelinated axons which are the neurosecretory cells. The cell bodies of these cells are located in the hypothalamus.

The secretory neurons have all the characteristics of typical neurons, including the ability to conduct an action potential, but have larger-diameter axons and well-developed synthetic components related to the production of antidiuretic hormone or (ADH) and oxytocin. Transported axonally, these hormones accumulate in axonal dilations called neurosecretory bodies or Herring bodies. The herring bodies release either oxytocin or ADH, which is carried away by nearby capillaries.

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Pituitary Gland Histology