Slide DMS158 [Human; pituitary gland, H&E]. Recall that this gland has a dual embryonic origin: oral cavity ectoderm (Rathke's pouch) and neuroectoderm (hypothalamic infundibular process). The former gives rise to the adenohypophysis (anterior lobe), the latter to the neurohypophysis (posterior lobe). The secretions of the two are remarkably different in origin and function.

Begin by identifying the capsule (dura mater), pars distalis, pars intermedia, pars nervosa. The pars tuberalis may be seen in the H&P slide along with a portion of the infundibular stalk with its cavity (continuous with 3rd ventricle of brain) lined with ciliated ependymal cells. Note the colloid-filled cysts in the pars intermedia. Now study the pars distalis at higher magnification, identifying blood sinusoids, and the characteristic secretory cells: acidophils, basophils, and chromophobes. In both slides the acidophils stain distinctly red, basophils blue, and chromophobes, as the name implies,weakly stained. Which hormones are produced by each of the cell types? What names are given to the functional types of acidophils and basophils?

Next, study the pars nervosa in detail. Note the strikingly different appearance from the pars distalis. Refresh your memory as to the significance of the hypothalamo-hypophysial tracts. Stored neurosecretory substance (Herring bodies) are not visible unless special staining techniques are used. Most of the nuclei seen in this region are those of specialized glial cells ("pituicytes").

Schematic of Pituitary Gland: 1. Anterior Lobe (adenohypophysis); 2. Posterior Lobe (neurohypophysis); 3. Pars Intermedia; 4. Hypothalamus