Final answer:
The assertion that the meninges have four layers is incorrect; there are three layers: the dura mater, arachnoid mater, and pia mater, which provide protection and support to the brain and spinal cord along with cerebrospinal fluid.
Step-by-step explanation:
The statement that the meninges are four layers of connective tissue membranes that surround the brain and spinal cord is false. In fact, the meninges consist of three layers of protective coverings. These layers are the dura mater, the arachnoid mater, and the pia mater. These membranes enclose the brain and spinal cord, providing protection alongside the bones of the skull and vertebrae. A special fluid called cerebrospinal fluid (CSF) is contained between two of the meningeal layers, offering additional cushioning and support.
The outermost layer, the dura mater, is a tough and fibrous layer that serves as a protective sheath. The arachnoid mater is a thinner layer that forms a loose sac around the central nervous system, and beneath it is a mesh-like structure called the arachnoid trabeculae. The closest layer to the brain and spinal cord is the pia mater, which is a delicate membrane that closely follows the contours of the brain.
The cerebrospinal fluid, found in the space between the arachnoid and pia maters, not only acts as a shock absorber but also serves to circulate nutrients and chemicals within the brain and spinal cord. This clear fluid is produced within the ventricles of the brain by a tissue called the choroid plexus.