Spinal Cord: Gross Anatomy

Inside the vertebral column is the slender and tubular structure called the spinal cord.

It is shorter than the vertebral column, with a length of about 45 cm. It extends from the medulla oblongata and terminates at the second lumbar vertebra.

There are two conspicuous enlargements along the length of the spinal cord with higher nerve concentrations.

The cervical enlargement is located between the fourth cervical and the first thoracic vertebra. The lumbosacral enlargement is present between the ninth and twelfth thoracic vertebra.

The spinal cord terminates as a cone-shaped tapering known as the conus medullaris. 

A thin strand of fibrous tissue called the filum terminale emerges from the conus medullaris. It anchors the spinal cord to the coccyx.

Extending from the conus medullaris is a collection of nerve roots that descend posteriorly. They are collectively referred to as the cauda equina.

The spinal cord has three protective connective tissue coverings called spinal meninges. The innermost layer is the pia mater, the middle layer is the arachnoid mater, and the outermost layer is the dura mater.