Chapter 3 Spine

LUMBAR VERTEBRAE

5

CERVICAL VERTEBRAE

7 C1, C2, & C7 ATYPICAL

Nerve Roots

At each vertebral level, a pair of nerve roots exits the spine through the intervertebral foramina on either side to form the right and left spinal nerves. They originate from the spinal cord and are separated into anterior and posterior roots. Surrounded by a sleeve of meninges, they join together outside the intervertebral foramen to form a spinal nerve. With the exception of the cervical vertebrae, the spinal nerves exit below the corresponding vertebrae In the cervical region, there are eight spinal nerves, because the C1 spinal nerves are found between the skull and C1. Consequently, cervical spinal nerves are above the corresponding vertebrae and spinal nerve 8 is found between C7 and T1.

Subarachnoid Space

Between the arachnoid mater and the pia mater. Continuous with the space of the cranium and filled with cerebrospinal fluid

INTERVERTEBRAL FORAMINA

Between the vertebrae, the opening formed on either side of the vertebral foramen that allows nerve roots to enter and exit the spinal column. Their size and shape depend on the alignment of the two adjoining vertebrae

PEDICLES

Bony projections that form the lateral walls of the vertebral foramen and connect the vertebral body to the transverse processes.

TRANSVERSE PROCESSES

Bony structures originating from the juncture of the laminae and pedicles that project laterally and provide a site of attachment for the deep muscles of the back. Cervical vertebrae have transverse foramina, and thoracic vertebrae have articular facets for the tubercles of the ribs.

ARTICULAR PROCESSES

Bony structures that are directly lateral to the vertebral foramen and extend upward and downward from the points at which the pedicles and laminae join. On the superior articular process, the upward projection, the articular surface faces posteriorly. The inferior articular process, the downward projection of bone, faces anteriorly. Together, they form the zygapophyseal joints between adjacent vertebrae.

Dura

The tough outer layer; surrounded by fat in the epidural space within the vertebral foramen. Like the other meningeal layers, it forms a sheath around the nerve roots within the intervertebral foramen.

THORACIC VERTEBRAE

12 FACETS FOR RIB ARTICULATIONS

Anulus Fibrosus

A concentric ring of fibrous tissue and fibrocartilage that forms the periphery of the disk.

Spinal Meninges

A continuation of the meningeal layers described within the head that surround and protect the spinal cord. As nerve roots exit through the intervertebral foramina, they are protected by a sleeve of meningeal layers that terminates as the spinal nerves are formed outside the spine.

SACRUM

Composed of five fused vertebral segments. The triangular bone that forms the posterior portion of the pelvis. Because the sacrum articulates with the fused ilia on either side, the foramina for the sacral spinal nerves open.

Intervertebral Disks

Connective tissue found between the vertebral bodies from C2 to the sacrum. They are of different sizes and help form the curvatures of the spine They make up approximately one-quarter of the length of the vertebral column. Although their primary function is to form part of the amphiarthrodial joints within the spine, they are also important in absorbing shock to the spine.

Posterior (dorsal) root ganglion

Formed by the collection of motor nerve cell bodies as the nerves pass through the intervertebral foramen.

Anterior (ventral) Nerve Root

Nerve fibers carrying sensory signals and terminating in the anterior spinal cord.

SPINOUS PROCESSES

Originate from the posterior union of the laminae. Bony processes that extend posteriorly and provide a site of attachment for the muscles of the back. Those on cervical vertebrae are shorter than those on thoracic and lumbar vertebrae, with the exception of the vertebra prominens on C7. The terminal processes of cervical vertebrae are usually bifid, unlike the single processes of other vertebrae.

Posterior (dorsal) nerve root

Posterior (dorsal) nerve root. Nerve fibers originating from the posterior spinal cord. Responsible for carrying motor stimuli to muscles within the body

Conus Medullaris

The caudal tip of the spinal cord found between L1 and L3

Pia Mater

The innermost layer. Continuous with the surface of the spinal cord and nerve roots.

Zygapophysis

The joint between the superior and inferior articular processes of adjacent vertebrae. In axial or sagittal section, the superior articular process is found anterior and lateral to the inferior articular process.

VERTEBRAL FORAMINA

The large triangular openings within the vertebrae between the body and the vertebral arch. Together, they create the opening for the spinal cord. Because the opening narrows as it extends downward, the foramina in the thoracic and lumbar vertebrae are smaller and rounder than those in the cervical vertebrae.

VERTEBRAL BODY

The largest and heaviest portion of the vertebra. Located anterior to the vertebral arch, forming the anterior margin of the vertebral foramen. Their size increases as one moves down the vertebral column . The bodies of thoracic vertebrae have superior and inferior costal facets for articulating with the ribs.

Anterior Longitudinal Ligament

The layer of dense connective tissue tightly attached to the anterior surfaces of vertebrae and intervertebral disks extending from C2 to the sacrum.

Posterior Longitudinal Ligament

The layer of dense connective tissue tightly attached to the posterior surfaces of vertebrae and intervertebral disks extending from C2 to the sacrum

Arachnoid Mater

The middle covering. Composed of thin, delicate fibers known as arachnoid trabeculae

LAMINAE

The remainder of the vertebral arch. They form the posterolateral walls of vertebral foramen, connecting the transverse processes with the spinous process.

Nucleus Pulposus

The soft, pulpy, elastic material found within the center of the disk.

COCCYX

Usually composed of four small rudimentary vertebral segments that form the caudal end of the spinal column. Common anomalies include three and five vertebral segments.

VERTEBRAL STRUCTURES

With the exception of the atlas (C1), all vertebrae contain a body, two pedicles, two laminae, and seven processes (two transverse, four articular, and one spinous).

Cauda Equina

Within the dural sheath, the bundle of lumbar and sacral nerves descending below the termination of the spinal cord. Resembles the caudal end of a horse (a horse's tail).