Seljaaju

Seljaaju (spinal cord) is a major component of the central nervous system that transmits information between the brain and the body and coordinates reflex actions. In an average adult, it extends from the medulla oblongata at the base of the skull to the conus medullaris around the level of the L1–L2 vertebrae and measures roughly 40–45 cm in length. Below the conus, the spinal canal contains the cauda equina, a bundle of nerve roots that continue to exit the vertebral column. The spinal cord is divided into segments corresponding to vertebral levels, with 31 pairs of spinal nerves emerging from its surface.

Anatomy and organization: The spinal cord is surrounded by three protective membranes—the meninges (dura mater, arachnoid mater, and pia mater)—and lies within the vertebral canal. The internal gray matter, shaped roughly like an H, contains neuronal cell bodies and is organized into dorsal (sensory) and ventral (motor) horns. White matter surrounds the gray matter and consists of ascending sensory tracts and descending motor tracts. Each spinal segment gives rise to a pair of dorsal (sensory) and ventral (motor) roots; the dorsal root carries sensory fibers and includes the dorsal root ganglion, while the ventral root carries motor fibers.

Circulation: The spinal cord receives blood from the anterior spinal artery and two posterior spinal arteries, with additional segmental medullary arteries contributing to regional perfusion. Venous drainage mirrors the arterial supply and drains into the surrounding venous system.

Clinical significance: Spinal cord function can be affected by trauma, inflammation, infection, tumors, vascular disorders, or degenerative diseases. Damage often produces motor, sensory, and autonomic deficits below the level of injury. Diagnosis commonly relies on magnetic resonance imaging (MRI); computed tomography (CT) and myelography may be used in certain cases. Treatment emphasizes stabilization, prevention of secondary injury, and rehabilitation, with prognosis depending on the type and timing of intervention.