− | This is the middle meningial layer and lies between the dura mater and the pia mater, the innermost meningeal layer. The arachnoid mater is a delicate structure and is constructed with non-vascular connective tissue. This layer also has small protrusions through the dura mater into the previously mentioned venous sinueses called '''Arachnoid villus''' and these allow [[Cerebral_Spinal_Fluid_-_Anatomy_%26_Physiology|cerebrospinal fluid]](CSF) to enter and exit the blood stream. These protrusions adhere to the inner surface of the skull via ''calvaria'' processes. | + | This is the middle meningial layer and lies between the dura mater and the pia mater, the innermost meningeal layer. The arachnoid mater is a delicate structure and is constructed with non-vascular connective tissue. This layer also has small protrusions through the dura mater into the previously mentioned venous sinueses called '''Arachnoid villus''' and these allow [[Cerebral_Spinal_Fluid_-_Anatomy_%26_Physiology|cerebrospinal fluid]] (CSF) to enter and exit the blood stream. These protrusions adhere to the inner surface of the skull via ''calvaria'' processes. |