Final answer:
The statement is true, the brain contains cavities known as ventricles filled with cerebrospinal fluid which provide cushioning and protection. There are four ventricles: the lateral ventricles, third ventricle, cerebral aqueduct, and fourth ventricle, each playing a vital role in protecting the brain and spinal cord.
Step-by-step explanation:
The statement that the brain is not completely solid and contains cavities, specifically ventricles, is true. The brain houses four main ventricles " the lateral ventricles, third ventricle, cerebral aqueduct, and fourth ventricle. The first two, the lateral ventricles, are connected to the third ventricle by the interventricular foramina and are located deep within the cerebrum. The third ventricle is situated between the left and right sides of the diencephalon, leading into the cerebral aqueduct through the midbrain, which then opens into the fourth ventricle. This fourth ventricle lies between the cerebellum and the pons and upper medulla.
These ventricles are a crucial component of the central nervous system (CNS) because they contain cerebrospinal fluid (CSF), which circulates throughout the CNS. The CSF is produced by ependymal cells within the choroid plexus and acts as a cushion for the brain, providing an essential protective function. The ventricles are evolutionary remnants of the neural tube's hollow center, which is evident during embryonic development.
Additionally, the brain is protected by the cranial cavity within the posterior (dorsal) cavity of the skull, while the spinal cavity or vertebral cavity contains the spinal cord. Collectively, these cavities protect and support the uninterrupted structure of the brain and spinal cord, further demonstrating the complexity of the body's protective mechanisms for these vital components of the nervous system.