Final answer:
The arachnoid mater has projections and villi that serve as one-way valves for the flow of CSF from the subarachnoid space into the dural sinuses.
Step-by-step explanation:
The brain mater that has projections and villi serving as one-way valves for the flow of cerebrospinal fluid (CSF) from the subarachnoid space into the dural sinuses is the arachnoid mater.
The arachnoid villi are outpocketings of the arachnoid membrane into the dural sinuses, allowing CSF to be reabsorbed into the bloodstream.
These arachnoid villi act as one-way valves, permitting the unidirectional flow of CSF from the subarachnoid space into the dural sinuses.