Anatomy and Physiology



Hypothalamic hormones that release or inhibit anterior pituitary hormones reach the anterior pituitary via a portal system

In the hypophyseal portal system, blood flows from capillaries in the hypothalamus into portal veins that carry blood to capillaries of the anterior pituitary

The superior hypophyseal arteries (branches of the internal carotid arteries) bring blood into the hypothalamus and the infundibulum

These arteries divide into a capillary network called the primary plexus of the hypophyseal portal system

From the primary plexus, blood drains into the hypophyseal portal veins that pass down the outside of the infundibulum

In the anterior pituitary, the hypophyseal portal veins divide again and form another capillary network called the secondary plexus of the hypophyseal portal system

Above the optic chiasm, neurosecretory cells synthesize the hypothalamic releasing and inhibiting hormones in their cell bodies and package the hormones inside vesicles

Which reach the axon terminals and nerve impulses stimulate the vesicles to undergo exocytosis

The hormones then diffuse into the primary plexus of the hypophyseal portal system then, the hypothalamic hormones flow with the blood through the portal veins and into the secondary plexus

Hormones secreted by anterior pituitary cells pass into the secondary plexus capillaries, which drain into the anterior hypophyseal veins and out into the general circulation

Anterior pituitary hormones then travel to target tissues throughout the body

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