Final answer:
The posterior pituitary, part of the diencephalon, is a neural extension of the hypothalamus connected by the infundibulum that stores and releases hormones produced by the hypothalamus.
Step-by-step explanation:
The posterior pituitary is an extension of the hypothalamus, classified under the diencephalon (option D) region of the brain. It is connected to the hypothalamus by the infundibulum, and it stores and secretes hypothalamic hormones. It differs from the anterior pituitary, which is glandular and develops from a different embryonic origin. The posterior pituitary, or neurohypophysis, contains axons descending from the hypothalamus, releasing hormones like oxytocin and antidiuretic hormone (ADH) into the bloodstream.
Highlighting its connection to the hypothalamus, the cell bodies of neurons in the paraventricular and supraoptic nuclei of the hypothalamus pass through the posterior pituitary via their axons. These neurons are crucial for hormone regulation in the body. The posterior pituitary itself does not produce the hormones but instead serves as a site for hormone release, orchestrated by neurosecretory cells within the hypothalamus.