The mater is composed of dense connective tissue, is highly vascular, and forms the internal periosteum of the cranial cavity.

The statement you provided seems to be missing a question. However, it appears to be discussing the dura mater, which is the outermost of the three layers of the meninges that surround the brain and spinal cord. The dura mater is indeed composed of dense connective tissue, is highly vascular (meaning it contains many blood vessels), and forms the internal periosteum of the cranial cavity. The periosteum is a membrane that covers the outer surface of all bones, except at the joints of long bones. In the skull, the dura mater serves as the internal periosteum. If you have a specific question related to this topic, please provide it.