The central nervous systemThe brain and spinal cord together make up the central nervous system. Nerves issue from both structures, passing out of the head and spinal canal, to supply all parts of the body, thereby allowing for voluntary movements to take place, various senses to be perceived and for the function of many internal organs to be regulated. Collectively, these nerves make up the peripheral nervous system. develops, in the womb, from a strip of tissueIn everyday speech a piece of tissue is a thin sheet of paper, used to wrap a present or, in a slightly different form, to blow the nose, or to be used in the toilet. In biology the word tissue refers to living material made up of cells or groups of cells of similar type or types. We may speak, for example, of nerve tissue or of fatty tissue, of glandular tissue or of connective tissue. Individual organs of the body, such as the brain, the heart, the liver or the kidneys, are made up of several tissue types, almost always including connective tissue., passing along the back of the embryo, and which then rolls itself into a tube before sinking below the skin surface. This primitive neural tubeDuring development in the womb, the central nervous system first begins to form as a strip of tissue running down the back. This strip then rolls itself into a tube which sinks below the surface. The layer which closes over this tube develops into the skin. The neural tube itself then develops into the brain at the head end and, below, into the spinal cord. then develops into the central nervous systemThe brain and spinal cord together make up the central nervous system. Nerves issue from both structures, passing out of the head and spinal canal, to supply all parts of the body, thereby allowing for voluntary movements to take place, various senses to be perceived and for the function of many internal organs to be regulated. Collectively, these nerves make up the peripheral nervous system., made up of 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.. In the fully developed adult (i.e. by the age of about 18) the original tubular configuration of the embryonic structure is represented by chambers in the centre of the brain, known as ventriclesThe brain is not an entirely solid organ. There are chambers within the brain, referred to as ventricles or, more correctly, cerebral ventricles, to distinguish them from the ventricles of the heart. They represent the remnants of the central canal of the developing central nervous system, although they have taken on a much more complex shape than the original embryonic structure. There are four in total, one each side of the midline (referred to as the lateral ventricles) and two more, in the midline, referred to as the third and fourth ventricles, albeit often using Roman numerals.. In the spine, the tubular structure is all-but obliterated, as 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. develops, being represented by just a narrow tube in the centre of the cord, known as the central canal.