Q.Rakesh got hurt on his head when he fell down from his motorbike. Which inner membranes must have protected his brain? What other roles do they have to play?

The brain (inside the cranium) and spinal cord (inside the vertebral canal) are both wrapped, inner to their bony coverings, in three protective connective-tissue membranes -- the meninges. The dura mater is the outermost, tough, thick, fibrous, non-vascular layer, attached to the cranium's inner surface. The arachnoid mater is the thin, web-like, non-vascular middle layer. The pia mater is the innermost, delicate, highly vascular membrane lying in direct contact with the nervous tissue itself. Cerebrospinal fluid (CSF), secreted by the choroid plexuses of the pia mater and by ependymal cells lining the brain's ventricles and the spinal cord's central canal, fills the subarachnoid space between arachnoid and pia and forms a cushion around and within the CNS. Slightly alkaline (specific gravity ~1.005, total volume ~100-120 cc), CSF is continuously produced and drained (via three openings in the medulla's roof), acting as a shock absorber against mechanical injury, maintaining constant intracranial pressure, exchanging nutrients/wastes between blood and brain tissue, and protecting the brain from desiccation. A separate blood-brain barrier (BBB), built from capillary endothelial cells and astrocytes, additionally screens what ions and large molecules can pass from blood into brain tissue.