Final answer:
The pia mater is a structure that covers the brain tightly and is rich in blood vessels.
Step-by-step explanation:
The structure that is covered by many blood vessels and adheres tightly to the surface of the brain is called the pia mater. The pia mater is the innermost layer of the meninges, a protective covering that surrounds the brain and spinal cord. It is a thin and delicate membrane that supplies blood vessels to the brain and helps protect it from injury.
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