Of the three membranous layers that invest 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 inner-most, known as the “pia”, can be likened to a thin skin, which is closely applied to the brain and cord 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.. At the lower end of 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., where it tapers down to the conusThe spinal cord is roughly cylindrical in shape, as it passes from the base of the brain, down along the spinal canal. At its lower end it tapers into a roughly conical shape. This part of the spinal cord is referred to as the conus. It contains nerve cells that supply important body functions such as bladder and bowel control, as well as sensation to the “private parts”., the pia continues on, in a downward direction, becoming the filum terminale, often referred to simply as the filum.