**Core Concept:** Posterior pituitary hormone secretion is a crucial aspect of the hypothalamic-pituitary-neurohypophyseal system, which involves the release of oxytocin and vasopressin from the posterior pituitary gland in response to specific stimuli. These hormones play vital roles in regulating fluid balance, parturition, and lactation.

**Why the Correct Answer is Right:** Vasopressin (also known as antidiuretic hormone, ADH) and oxytocin are neurohypophyseal hormones synthesized in the hypothalamus, a region of the brain responsible for regulating various endocrine and autonomic functions. The hormones are then transported through the neurohypophyseal tracts (also known as neurohypophyseal fibers or neurohypophyseal tracts) and released into the anterior pituitary lobe, where they act on specific receptors on the capillaries surrounding the pituitary stalk. This process ensures that the hormones are directed to the target organs and not diffusely released into the bloodstream.

**Why Each Wrong Option is Incorrect:**

A. False: Posterior pituitary hormone secretion occurs through the neurohypophyseal tracts, not the hypothalamus.
B. False: The posterior pituitary, not the hypothalamus, is responsible for oxytocin secretion.
C. False: The hypothalamus synthesizes and releases the hormones; the posterior pituitary receives and releases them.
D. False: The hypothalamus is the primary site of oxytocin and vasopressin synthesis, not the posterior pituitary gland.

**Clinical Pearl:** Understanding the anatomy and physiology of the hypothalamic-pituitary-neurohypophyseal system is crucial for understanding the regulation of water and electrolyte balance, labor progression, and breast milk secretion. Mistakes in this system can lead to serious medical conditions like diabetes insipidus and pituitary gland dysfunction.

✓ Correct Answer: C. The hypothalamo-hypophyseal tract originating from magnocellular neurons in the supraoptic and paraventricular nuclei