Meningo (_Meengogo_) - see Menning - (lat. meningō, from meningo - brain), extraorgan connective tissue membranes of the brain and spinal cord, consisting of connective tissue with blood and lymphatic vessels and nerves. They develop from mesenchyme, fill the gaps between the outer sheets of the periosteum, are part of the pia mater, envelop the vessels, meninges, then the spinal cord, forming the fatty, cerebrospinal and arachnoid layers. There are: * hard M. - covers the spinal cord on all sides; * soft M., consisting of two leaves - outer and inner, running parallel to the surface of the spinal cord; the internal tendon sheath of the spinal nerve lies between these layers. Blood vessels pass in thin channels formed by wide internal longitudinal loops of the outer leaf, containing special tissue that can increase sharply during embryonic growth. Outside, M. is covered with periosteum. The mucous membrane lining the pericerebral part of the skull and vertebral arches ossifies (diploë) several weeks after birth.