wirbel

Wirbel is a German noun with several related meanings. In anatomy, der Wirbel refers to a vertebra, one of the bones that form the vertebral column and protect the spinal cord. There are seven cervical, twelve thoracic, and five lumbar Wirbel in the typical adult, with additional sacral and coccygeal segments in some classifications. Each Wirbel consists of a vertebral body, a vertebral arch with pedicles and laminae, and projections that establish joints with adjacent Wirbel and serve as attachment points for muscles. When the Wirbel align, they enclose the spinal canal through which the spinal cord runs. Intervertebral discs separate neighboring Wirbel and provide shock absorption and mobility. Common conditions affecting the Wirbel and spine include fractures, degenerative changes such as spondylosis, herniated discs, and spinal stenosis.

In physics and fluid dynamics, a Wirbel, or vortex, is a region in a fluid where flow revolves around an axis, producing a rotating motion. Vortices can vary in size from microscopic to atmospheric scales and are characterized by quantities such as vorticity and circulation. They occur in air and water and are involved in many phenomena, from natural ones like tornadoes and whirlpools to engineered ones such as smoke rings and wake vortices behind aircraft.