Hypophyseal Portal System: Hypothalamic hormones reach the anterior pituitary through a portal system. In this system, blood flows from capillaries in the hypothalamus into portal veins that carry blood to capillaries of the anterior pituitary. Neurosecretory Cells : synthesize the hypothalamic releasing and inhibiting hormones in their cell bodies and package the hormones inside vesicles to undergo exocytosis. The hormones then diffuse into the primary plexus of the hypophyseal portal system. Hypothalamic hormones then flow with the blood through the portal veins into the secondary plexus. The hypothalamic hormones than act on Pituitary Cells which secrete their hormones into the secondary plexus capillaries draining into the anterior hypophyseal veins. From there the hormones flow out into general circulation and to target tissues throughout the body.
Anterior Pituitary aka Adenohypophysis
This part of the pituitary secretes hormones that regulate a wide variety of bodily activities.
The adenohypophysis consists of the pars tuberalis & the pars distalis, which are epithelial up- growths of the oral cavity.
Control is regulated in 2 ways :
Neurosecretory Cells in the Hypothalamus secrete 5 releasing hormones which stimulate the release of hormones from the anterior pituitary and 2 inhibitory hormones which suppress secretion from the anterior pituitary. Negative Feedback in the form of hormones released by target cells decreases secretions of 3 types of anterior pituitary cells: thyrotrophs, gonadotrophs, corticotrophs. These levels decrease as blood levels of their target gland hormones increase. They do not have inhibiting hormones.
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