In the central nervous system, there are three different layers that cover the spinal cord and brain. These are called the meninges, and their three levels consist of the: pia, arachnoid, and dura mater. Bone is situated above these layers, followed by periosteum (a fibrous membrane that covers bone) and skin.The dura mater is the top layer of the meninges, lying beneath the bone tissue.This material at times opens into sinus cavities (spaces) located around the skull.he dura mater is the top layer of the meninges, lying beneath the bone tissue. This material at times opens into sinus cavities (spaces) located around the skull.
Planet Earth Making Mountains Planet Earth filmmakers came out in the rugged mountains of Nepal in hopes of filming the elusive snow leopard for the Mountains episode. 01:51.
Background. The April 22 Earth Day, founded by Senator Gaylord Nelson, was first organized in 1970 to promote ecology and respect for life on the planet as well as to encourage awareness of the growing problems of air, water and soil pollution.hile some people celebrate Earth Day around the time of the March Equinox, others observe the occasion on April 22 each year. Earth Day aims to inspire awareness of and appreciation for earth's environment. It's not to be confused with Earth Hour. People unite on Earth Day to appreciate and respect earth's environment.