What is the name of the thin, delicate middle layer of the meninges?

The thin, delicate middle layer of the meninges is known as the arachnoid membrane. This layer lies between the outer dura mater and the inner pia mater, providing a cushioning effect for the brain and spinal cord. The arachnoid membrane is named for its spider web-like appearance, which allows it to effectively encase the central nervous system while also separating it from the surrounding structures.

In addition to providing a protective barrier, the arachnoid membrane plays a crucial role in the circulation of cerebrospinal fluid (CSF), which is important for maintaining homeostasis and providing buoyancy to the brain. The CSF circulates between the arachnoid layer and the pia mater in a space known as the subarachnoid space.

The other options do not represent the middle layer of the meninges. The hypothalamus is a region of the brain responsible for various hormonal and autonomic functions. The cerebral cortex is the outer layer of the brain involved in complex functions like perception and decision-making. The dura mater is the outermost layer of the meninges and is much thicker and tougher than the arachnoid membrane.