21.8:
The Pituitary Gland
The pituitary gland is a small endocrine organ located in the sphenoid bone under the hypothalamus.
Primarily, the pituitary in adults has two distinct anatomical and functional regions— the anterior and posterior lobes.
The two parts of the anterior lobe— pars distalis and pars tuberalis, comprise glandular epithelial tissue, which produces various hormones.
The anterior lobe has a vascular connection with the hypothalamus via the hypophyseal portal system.
The hypothalamic hormones secreted by cells of the ventral hypothalamus travel through this portal system and control the hormone secretion by cells of the anterior lobe.
The posterior pituitary lobe also has two parts, infundibulum—a funnel-shaped stalk and pars nervosa.
The infundibulum allows the passage of the supra-optic and paraventricular nuclei axons of the hypothalamic-hypophyseal tract, maintaining a neural connection with the hypothalamus.
This tract delivers the ready-made hormones secreted by these hypothalamic neurosecretory cells into the posterior pituitary lobe, where they are stored until release.
21.8:
The Pituitary Gland
The pituitary is a small endocrine organ in the sphenoid bone under the hypothalamus. Primarily, the pituitary in adults has two distinct anatomical and functional regions— the anterior and posterior lobes. During human fetal development, a third pituitary gland region called the pars intermedia atrophies and disappears. However, some of its cells migrate and exist adjacent to the anterior pituitary in adults.
- The anterior lobe comprises the pars distalis and the pars tuberalis. These areas consist of glandular epithelial tissue that produces various hormones. The anterior lobe is linked to the hypothalamus through the hypophyseal portal system. The hormones secreted by the ventral hypothalamus cells travel through this portal system and regulate hormone-secreting cells of the anterior lobe.
The posterior pituitary lobe has two parts: the infundibulum, a funnel-shaped stalk, and the pars nervosa. The infundibulum allows the passage of the supra-optic and paraventricular nuclei axons of the hypothalamic-hypophyseal tract, maintaining a neural connection with the hypothalamus. The hypothalamic-hypophyseal tract delivers hormones secreted by hypothalamic neurosecretory cells into the posterior pituitary lobe for storage and release.