How is the pituitary gland connected to the hypothalamus?

The correct choice highlights that the pituitary gland is connected to the hypothalamus via the infundibulum, which is a slender stalk-like structure. This connection is crucial for the regulation of various bodily functions, as the hypothalamus sends signals to the pituitary gland to release hormones that control important processes such as growth, metabolism, and stress response. The infundibulum acts as the physical conduit for neurohormones produced in the hypothalamus to be delivered to the pituitary gland, demonstrating the key role this connection plays in the endocrine system.

The other mentioned structures do not serve this specific function. The corpus callosum is involved in communication between the left and right hemispheres of the brain but is not directly related to the connection between the hypothalamus and pituitary. The vagus nerve primarily carries signals to and from the brain to the viscera, not connecting the pituitary. The fornix is associated with the limbic system and is not involved in the hormonal connections between the hypothalamus and the pituitary gland.