These are membranes which enclose the brain and the spinal cordThe main nerve trunk running down the spinal canal and connecting the individual’s mind and consciousness to the rest of his or her body. It is about the size of a person’s little finger, in diameter. It cannot repair itself if damaged.. There are three, which are very different from one another in nature. The duraThis is the outer, most prominent and the toughest of the three different membranes that invest the brain and spinal cord. It also forms the lining of the cranial cavity and the spinal canal. Looked at as a whole, the dura can be envisaged as a balloon with a long sausage skin hanging below it. Within the dura the brain and spinal cord are bathed in cerebrospinal fluid. is the outermost, lining the inside of the skull and the spinal canalThe individual bones that comprise the spinal column are made up of a weight-bearing “body” and other components which, together, form a ring of bone, behind the body. These individual vertebrae, joined together as the spinal column, therefore, create a canal running down the entire length of the spine.. It is tough and waterproof, retaining the cerebrospinal fluidThis clear, water-like fluid forms, for the most part, within the brain, more specifically inside the ventricles of the brain. Blood flows through structures inside the ventricles, called the choroid plexuses, and clear fluid is produced as a result, passing into the ventricle. This process is akin to blood flowing through the kidneys and urine being produced as a result. An important difference is that, unlike urine, the cerebrospinal fluid is not passed out of the body periodically. Instead, the fluid is re-absorbed back into the blood stream, mostly via the arachnoid granulations, into the cerebral venous sinuses. In the course of a 24-hour period, most healthy adults will produce about 500mls (or a pint) of cerebrospinal fluid, although at... that bathes the brain and spinal cordThe main nerve trunk running down the spinal canal and connecting the individual’s mind and consciousness to the rest of his or her body. It is about the size of a person’s little finger, in diameter. It cannot repair itself if damaged.. The innermost layer is the pia, which is like a thin skin applied closely to the surface of the brain and spinal cordThe main nerve trunk running down the spinal canal and connecting the individual’s mind and consciousness to the rest of his or her body. It is about the size of a person’s little finger, in diameter. It cannot repair itself if damaged.. Between these two layers is the arachnoidA thin, transparent membrane, lying immediately over the brain and spinal cord, and in turn being surrounded by dura. The arachnoid forms thin membranes and strands likened by early anatomists to a spider’s web. Hence its name, referring to spiders, as in “arachnophobia”, which means the fear of spiders., which is a loose, net-like structure made up of sheets and strands of thin, translucent material, stretching between the duraThis is the outer, most prominent and the toughest of the three different membranes that invest the brain and spinal cord. It also forms the lining of the cranial cavity and the spinal canal. Looked at as a whole, the dura can be envisaged as a balloon with a long sausage skin hanging below it. Within the dura the brain and spinal cord are bathed in cerebrospinal fluid. and the pia. The cerebrospinal fluidThis clear, water-like fluid forms, for the most part, within the brain, more specifically inside the ventricles of the brain. Blood flows through structures inside the ventricles, called the choroid plexuses, and clear fluid is produced as a result, passing into the ventricle. This process is akin to blood flowing through the kidneys and urine being produced as a result. An important difference is that, unlike urine, the cerebrospinal fluid is not passed out of the body periodically. Instead, the fluid is re-absorbed back into the blood stream, mostly via the arachnoid granulations, into the cerebral venous sinuses. In the course of a 24-hour period, most healthy adults will produce about 500mls (or a pint) of cerebrospinal fluid, although at... flows along the subarachnoid channelsCerebrospinal fluid forms, for the most part, within the ventricles of the brain. From there it flows out, at the base of the brain, and on over the surface of the brain, then to be re- absorbed back into the bloodstream, mainly into the superior sagittal sinus. Some also flows into the spinal canal. The ventricles and other courses along which the cerebrospinal fluid flows, inside the head and the spinal canal, make up the subarachnoid channels. The term subarachnoid space is commonly used, arguably in error as it implies that these channels are empty, whereas they are, in life, “flooded” with cerebrospinal fluid., between the arachnoidA thin, transparent membrane, lying immediately over the brain and spinal cord, and in turn being surrounded by dura. The arachnoid forms thin membranes and strands likened by early anatomists to a spider’s web. Hence its name, referring to spiders, as in “arachnophobia”, which means the fear of spiders. and the pia.