Spinal Cord: Gross Anatomy

The spinal cord extends from the medulla oblongata at the base of the brainstem and terminates at the conus medullaris near the first and second lumbar vertebrae. In adults, the spinal cord measures approximately 45 centimeters in length, significantly shorter than the vertebral column, which continues to extend beyond the spinal cord's termination point.

The cervical enlargement, located between the fourth cervical and first thoracic vertebra, contains concentrated nerve roots controlling the upper limbs. The lumbosacral enlargement, positioned between the ninth and twelfth thoracic vertebrae, innervates the lower limbs. Both enlargements are crucial for limb movement and sensory processing.

The cauda equina is a bundle of nerve roots that descends posteriorly from the conus medullaris, resembling a horse's tail. These nerve roots fan out to reach various parts of the lower body, providing motor and sensory functions to the legs and lower regions of the body.

The spinal meninges consist of three protective layers: the pia mater directly adheres to the spinal cord surface, the arachnoid mater provides a protective barrier, and the dura mater forms a tough outer sheath. Together, they offer protection, physical stability, and shock absorption. The subarachnoid space between the pia and arachnoid mater contains cerebrospinal fluid.

The filum terminale is a thin strand of fibrous tissue that emerges from the conus medullaris. It extends downward to anchor the spinal cord to the coccyx, stabilizing the spinal cord within the vertebral column and preventing excessive movement during body motion.

The conus medullaris is the cone-shaped tapering at the terminal end of the spinal cord, located near the first and second lumbar vertebrae. It marks the point where the spinal cord ends and from which the filum terminale and cauda equina emerge.

The spinal cord serves as the main pathway for information traveling between the brain and body, playing a fundamental role in nearly all bodily functions. It enables simple reflexes and complex motor movements by transmitting sensory information upward to the brain and motor commands downward to the body.