Meninges

The spinal dura mater forms a tough, tubular dural sheath that extends into the vertebral canal and surrounds the spinal cord. There is no connection between the dural sheath and the vertebrae that form the canal there is a cavity called the epidural space which is highly vascular and contains loose and adipose tissue which forms a protective pad around the spinal cord. The arachnoid membrane is the middle of the meningeal layers and as its name implies, appears spider-like or more specifically, has the appearance of a spider web. The subarachnoid space, located between the arachnoid membrane and the pia mater is maintained by delicate, web-like strands that connect the arachnoid membrane and the pia mater. Cerebrospinal fluid is a clear, lymph-like fluid that forms a protective cushion around and within the central nervous system. Although produced in the ventricles of the brain, cerebrospinal fluid is found abundantly in the subarachnoid space where it buoys the central nervous system and protects it from injury. It is this fluid that is removed for analysis with lumbar puncture or spinal tap. The pia mater is a thin layer of modified loose connective tissue that follows the irregular contours of the brain and spinal cord. It is highly vascular and functions to support the vessels that nourish underlying cells of the brain and spinal cord.