The pituitary gland (hypophysis) is considered to be a master gland because of the hormonal control it exerts on many other glands. Study the diagram of the pituitary gland noting the relationships between the anterior and posterior lobes, the vascular supply, and the hypothalamus of the brain. The hypothalamus-hypophyseal portal system has a central role in pituitary function because it carries regulatory hormones from the median eminence of the hypothalamus to the endocrine cells of the anterior pituitary. Review the tables below summarizing the hormones of the hypothalamus and anterior pituitary and their actions.

• Examine the image at the right and these two sections of pituitary gland (sample 1, sample 2). Identify the anterior pituitary, the posterior pituitary, and the intervening pars intermedia with cysts (arrows) representing remnants of Rathke's pouch. Note the abundance of large capillaries among the clusters of glandular epithelial cells in the anterior pituitary. The pars intermedia, as seen in this specimen, is poorly developed in humans.

This slide of pituitary shows a section of the gland prepared with a special trichrome stain that demonstrates the different staining properties of the secretory cells in the anterior pituitary. Identify acidophils (A), basophils (B), chromophobes (C), and sinusoids (S) in this specimen and in the images below.

Finally, examine the ultrastructural features of the endocrine cells in the anterior pituitary. The TEM images below show lactotrophs forming and releasing their secretory granules containing prolactin.

Posterior pituitary is next.