Ryggsegment

Ryggsegment, often referred to as a spinal segment in English, is the functional unit of the spinal cord and its associated spinal nerve pair that supplies a specific region of the body. Each ryggsegment includes the ventral (motor) and dorsal (sensory) roots, the dorsal root ganglion, the corresponding segment of the spinal cord, and the vertebral level associated with that segment.

Humans have 31 pairs of spinal nerves organized into cervical (8), thoracic (12), lumbar (5), sacral (5), and coccygeal (1). Spinal cord segments give rise to these nerve pairs, providing both motor and sensory innervation to their designated dermatomes and myotomes. The spinal cord itself is shorter than the vertebral column in adults, so cord segments do not line up exactly with the vertebral levels; nerve roots traverse the space below the corresponding segment to reach their intervertebral foramina.

Functions attributed to each ryggsegment include transmission of motor commands to skeletal muscles and reception of sensory information from the skin, muscles, and internal organs. Dermatomes and myotomes describe the pattern of segmental innervation and are used clinically to localize lesions.

Clinical relevance is high for radiculopathy, spinal cord injury, and other compressive or inflammatory conditions, where signs and symptoms often correspond to a specific ryggsegment. Diagnosis and treatment decisions frequently rely on understanding the segmental organization of the spinal cord and nerves.

See also: spinal cord, vertebral column, nerve root, dermatomes, myotomes, cauda equina.