thecal

Thecal is an adjective derived from the Greek thekē, meaning a case, sheath, or covering. In scientific terminology, it is used to describe a sheath-like structure associated with a particular organ or region.

In human anatomy and medicine, the most common usage refers to the thecal sac, also called the dural sac, which encloses the spinal cord and cauda equina. This membrane contains cerebrospinal fluid and extends from the foramen magnum to the sacral canal. The space within the thecal sac is known as the thecal space, and medical procedures such as lumbar puncture (spinal tap) or intrathecal injections involve accessing the thecal space to sample CSF or deliver medication.

Outside of the clinical context, thecal is used in various biological sciences to denote a sheath-like covering of a specific structure, with its exact meaning varying by organism or context. As a descriptive root, thecal conveys the idea of a surrounding envelope rather than pointing to a single standardized anatomical feature beyond the dural sac.

Etymology and related terms: thecal derives from the Greek thekē. Related terms include theca, which is the noun for a surrounding case or sheath, and the dural sac, the broader anatomical structure that contains the thecal space in the spinal canal.

See also: theca, dural sac, cerebrospinal fluid, lumbar puncture.