Which structure is responsible for the brain's protection?

The skull is crucial for protecting the brain because it encases the brain in a hard, bony structure, thereby providing a barrier against physical impacts and damage. This protective barrier helps prevent injury from external forces, such as blows or falls, which could lead to serious consequences like concussions or traumatic brain injuries. The skull's design not only guards against direct trauma but also provides a stable environment within which the brain can function properly.

While other structures mentioned, like the ribs and vertebrae, provide protection to other vital organs and areas of the body, they do not offer direct protection to the brain. The heart, although vital for circulation and overall health, does not play a role in protecting the brain. Hence, the skull is specifically designed for this protective role, making it the correct answer in this context.