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The hypophyseal portal system also plays an important role in several diseases involving the pituitary and central nervous system. In several cases of hypophyseal and pituitary metastatic tumors, the portal system acts as the pathway for metastasis from the hypothalamus to the pituitary. That is, cancerous cells from the hypothalamus multiply ...
Many of its neurons project to the posterior pituitary where they secrete oxytocin, and a smaller amount of vasopressin. Other secretions are corticotropin-releasing hormone (CRH) and thyrotropin-releasing hormone (TRH). [1] CRH and TRH are secreted into the hypophyseal portal system, and target different neurons in the anterior pituitary.
The posterior pituitary consists mainly of neuronal projections of magnocellular neurosecretory cells extending from the supraoptic and paraventricular nuclei of the hypothalamus. These axons store and release neurohypophysial hormones oxytocin and vasopressin into the neurohypophyseal capillaries, from there they get into the systemic ...
HPG regulation in males, with the inhibin/activin system playing a similar role on GnRH-producing cells. The hypothalamus is located in the brain and secretes GnRH. [1] GnRH travels down the anterior portion of the pituitary via the hypophyseal portal system and binds to receptors on the secretory cells of the adenohypophysis. [2]
Anterior pituitary. In the hypothalamic–adenohypophyseal axis, releasing hormones, also known as hypophysiotropic or hypothalamic hormones, are released from the median eminence, a prolongation of the hypothalamus, into the hypophyseal portal system, which carries them to the anterior pituitary where they exert their regulatory functions on ...
Endocrine cells of the anterior pituitary are controlled by regulatory hormones released by parvocellular neurosecretory cells in the hypothalamic capillaries leading to infundibular blood vessels, which in turn lead to a second capillary bed in the anterior pituitary. This vascular relationship constitutes the hypophyseal portal system.
The median eminence is a part of the hypothalamus from which regulatory hormones are released. [2] [7] It is integral to the hypophyseal portal system, which connects the hypothalamus with the pituitary gland. The pars nervosa (part of the posterior pituitary gland) is continuous with the median eminence via the infundibular stalk.
The hypothalamus produces the hormones oxytocin and vasopressin in its endocrine cells (left). These are released at nerve endings in the posterior pituitary gland and then secreted into the systemic circulation. The hypothalamus releases tropic hormones into the hypophyseal portal system to the anterior pituitary (right).