What protects the human brain?

The skull, or cranial cavity, serves as the primary protective barrier for the human brain. It is a bony structure that encases the brain, providing a rigid framework that shields it from physical trauma, such as impacts or falls. The design of the skull not only protects the brain but also supports its shape, separating it from other structures in the head.

In addition to providing a physical barrier, the cranial cavity is filled with cerebrospinal fluid, which cushions the brain and helps absorb shocks, further safeguarding the delicate brain tissue from injury. This combination of bone and fluid creates an effective protective environment for the brain, which is vital for the body's overall function and health.

Other options, while related to the body's structure, do not serve the same protective role for the brain. The vertebrae, for example, protect the spinal cord, while the coccyx is part of the lower spine with no protective function for the brain. Fontanels are the soft spots in an infant's skull that allow for growth and flexibility during birth; they do not provide protection in the same way the fully formed skull does.