The Anatomy of Pituitory Gland

The Correct options are Answer: a, b



The anterior pituitary gland is the adenohypophysis which constitutes 80% of the gland. The posterior pituitary, the neurohypophysis, constitutes the remainder and should be considered virtually an extension of the hypothalamus of the brain. The pituitary resides within bony confines of the sella turcica (Turkish saddle) and is bordered laterally by the cavernous sinuses (venous), inferiorly and anteriorly by the sphenoid sinus (air), posteriorly by the dorsum sella and superiorly by the membranous diaphragma sella. The cavernous sinuses each contain the siphon region of the internal carotid artery and portions of the cranial nerves III, IV, V and VI all within the venous plexus. The optic chiasm lies immediately above the diaphragma sella. Directly below the anterior and inferior portions of the sella is the aerated sphenoid sinus. This is sufficiently large in 97% of the patients to allow a transnasal, transsphenoidal surgical approach to the pituitary.

The adenohypophysis is regulated by a portal venous system between the median eminence of the hypothalamus and the adenohypophysis itself. This system involves a transport of (1) thyrotropin-releasing hormone (TRH), to stimulate the secretion of the thyroid-stimulating hormone (TSH); (2) corticotropin-releasing hormone, to stimulate adrenocorticotropic hormone (ACTH); (3) growth hormone-releasing hormone, to stimulate secretion of growth hormone (GH); (4) gonadotropin-releasing hormone, to stimulate luteinizing hormone (LH) and follicle-stimulating hormone (FSH); and (5) prolactin-inhibitory factor (dopamine), to inhibit prolactin. The neurohypophysis is regulated by means of direct transport of hormones through nerve fibers from the supraoptic and paraventricular nuclei in the hypothalamus. The neurohypophysis is a virtual extension of the hypothalamus. Products of the neurohypophysis are antidiuretic hormone (ADH; vasopressin) and oxytocin. The pituitary gland is not known to release serotonin.

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