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.
A cross section of the human spinal cord. Conus medullaris is the is the technical name for the lower end of the spinal cord. Damage to the conus medullaris may cause pain in the lower back. The conus medullaris originates at the base of the brain and extends to the lower end of the spinal cord. Conus medullaris syndrome may cause difficulty walking as well as numbness and weakness in the legs.