The Pituitary Gland

The pituitary gland is a small endocrine organ located in the sphenoid bone beneath the hypothalamus. This strategic positioning allows it to maintain close anatomical and functional connections with the hypothalamus, enabling coordinated control of hormone secretion throughout the body.

The adult pituitary has two distinct anatomical and functional regions: the anterior lobe and the posterior lobe. The anterior lobe comprises the pars distalis and pars tuberalis, which contain glandular epithelial tissue that produces various hormones. The posterior lobe consists of the infundibulum and pars nervosa.

The hypothalamus controls the anterior pituitary through the hypophyseal portal system, a vascular connection between the two structures. Hypothalamic hormones secreted by ventral hypothalamus cells travel through this portal system and regulate hormone secretion by anterior lobe cells, enabling integrated endocrine control.

The hypothalamic-hypophyseal tract is a neural pathway that passes through the infundibulum, a funnel-shaped stalk connecting the hypothalamus to the posterior pituitary. This tract carries axons from the supra-optic and paraventricular nuclei, delivering ready-made hormones from hypothalamic neurosecretory cells for storage and release by the posterior pituitary.

The posterior pituitary maintains a neural connection with the hypothalamus via the hypothalamic-hypophyseal tract, whereas the anterior pituitary has a vascular connection through the hypophyseal portal system. The posterior lobe stores hormones produced by hypothalamic neurons, while the anterior lobe produces its own hormones in response to hypothalamic signals.

During fetal development, a third pituitary region called the pars intermedia atrophies and disappears in most individuals. However, some of its cells migrate and persist adjacent to the anterior pituitary in adults, though they no longer form a distinct functional lobe in the mature gland.

The anterior pituitary lobe comprises glandular epithelial tissue organized into the pars distalis and pars tuberalis. This specialized tissue produces and secretes various hormones in response to signals from the hypothalamus, making it an active endocrine organ rather than a storage site for hormones.