Releasing hormones from the hypothalamus travel to the pituitary through what vascular system?

• A. Lymphatic vessels
• B. Direct arterial supply
• C. Hypothalamic-pituitary portal blood vessels
• D. Venous drainage only

Answer: (C)

The releasing hormones from the hypothalamus travel to the pituitary through a specialized vascular system called the hypothalamic-pituitary portal system. Hypothalamic neurons release these hormones into a capillary network in the median eminence, forming the primary capillary plexus. They are then carried by portal veins directly to the anterior pituitary, where they encounter a second capillary plexus and exert their effects on pituitary cells. This arrangement concentrates the hormones where they’re needed, allowing precise regulation of pituitary secretion with minimal dilution in the general circulation. Other pathways like lymphatic vessels, direct arteries, or venous drainage alone wouldn’t provide this targeted, efficient delivery.