Diagram of the layers within Earth's atmosphere. Troposphere. The troposphere starts at the Earth's surface and extends 8 to 14.5 kilometers high (5 to 9 miles). This part of the atmosphere is the most dense.Almost all weather is in this region. Stratosphere. The stratosphere starts just above the troposphere and extends to 50 kilometers (31 miles) high.he troposphere starts at the Earth's surface and extends 8 to 14.5 kilometers high (5 to 9 miles). This part of the atmosphere is the most dense. Almost all weather is in this region.
conus. n, pl-ni. 1. (Anatomy) anatomy zoology any of several cone-shaped structures, such as the conus medullaris, the lower end of the spinal cord. 2. (Zoology) anatomy zoology any of several cone-shaped structures, such as the conus medullaris, the lower end of the spinal cord. continental United States.
The spinal cord ends near the first lumbar vertebra in the lower back, forming the conus medullaris. The fibrous extension of the spinal cord is the filum terminale. The bundle of nerve roots below the conus medullaris is named the cauda equina (see Multimedia File 1). Compression or inflammation of the nerve roots can cause symptoms of pain, altered reflexes, decreased strength, and decreased sensation.