Does regulating hormones from the hypothalamus travel by arteries to pituitary?

No, the regulating hormones from the hypothalamus do not travel by arteries to the pituitary. Instead, they are transported via the hypothalamic-pituitary portal system, a specialized network of blood vessels that connects the hypothalamus and the anterior pituitary gland.

Here's how the hypothalamic-pituitary portal system works:

Hypothalamic Releasing Hormones: The hypothalamus produces releasing hormones (RHs) and releasing inhibitory hormones (RIHs) that control the secretion of hormones from the anterior pituitary.

Portal Blood Vessels: The hypothalamus has specialized capillaries called fenestrated capillaries, which allow substances to pass through more easily than ordinary capillaries. These capillaries form a dense network of blood vessels known as the primary capillary plexus.

Hypothalamo-Hypophyseal Veins: The primary capillary plexus converges into small veins called hypothalamo-hypophyseal veins, which carry the releasing hormones and inhibitory hormones towards the anterior pituitary.

Secondary Capillary Plexus: The hypothalamo-hypophyseal veins drain into a secondary capillary plexus within the anterior pituitary. These capillaries are also fenestrated, allowing the hormones to diffuse out of the bloodstream and reach the pituitary cells.

Target Pituitary Cells: The releasing hormones and inhibitory hormones bind to specific receptors on the target cells in the anterior pituitary, stimulating or inhibiting the release of pituitary hormones.

By using the hypothalamic-pituitary portal system, the hypothalamus can directly regulate the secretion of pituitary hormones without the need for arterial blood flow. This specialized system allows for precise control and rapid communication between the hypothalamus and the anterior pituitary.