What are the three membranes that cover the brain called?

The membranes that envelop the brain are collectively known as the meninges. There are three distinct layers within this group: the dura mater, arachnoid mater, and pia mater. Each layer serves a specific purpose in protecting the brain and helping maintain its structural integrity.

The dura mater is the outermost layer and is tough and durable, providing a protective barrier against physical impacts. The arachnoid mater lies beneath the dura mater and contains cerebrospinal fluid in its subarachnoid space, which acts as a cushion for the brain. The pia mater is the innermost layer, intimately adhering to the brain's surface and following the contours of the brain’s structure, providing further protection and supply of blood vessels.

The other terms listed—cranium, arteries, and nerves—do not refer to membranes covering the brain. The cranium is the bony structure that houses and protects the brain, while arteries are blood vessels that carry blood away from the heart, and nerves are part of the nervous system that transmit signals. Understanding the role of the meninges is crucial in the study of brain anatomy and its protective mechanisms.