THE HYPOPHYSIS

The hypophysis (pituitary gland; Figure 8-52) sus­pended below the hypothalamus by the infundibulum, consists of two parts. One, the neurohypophysis (poste­rior lobe), is an outgrowth of the brain itself; the other, the adenohypophysis, is developed from oral ectoderm (p. 217) and comprises anterior and intermediate lobes. Interspecific differences in the topographical interrela­tionship of the lobes are not of present concern (see Figure 6-2).

The three lobes produce or store several hormones (p. 217). The posterior lobe hormones (vasopressin and oxytocin) are produced by neurosecretory cells within the supraoptic and paraventricular nuclei of the hypo­thalamus and are conveyed along the axons for direct release into the neurohypophysial capillary bed (see Figure 6-3).