Atlas of Anatomy (eBook)

Fig. 2.1 Vertebral column
Left lateral view.

Clinical box 2.1

Spinal development

The characteristic curvatures of the adult spine appear over the course of postnatal development, being only partially present in a newborn. The newborn has a “kyphotic” spinal curvature (A); lumbar lordosis develops later and becomes stable at puberty (C).

Fig. 2.2 Normal anatomical position of the spine
Left lateral view.

Clinical box 2.2

Abnormal Vertebral Column Curvatures

Fig. 2.3 Bones of the vertebral column
The transverse processes of the lumbar vertebrae are originally rib rudiments and so are named costal processes.

Fig. 2.4 Structural elements of a vertebra
Left posterosuperior view. With the exception of the atlas (C1) and axis (C2), all vertebrae consist of the same structural elements.

Fig. 2.5 Typical vertebrae
Superior view.

Fig. 2.6 Cervical spine
Left lateral view.

Fig. 2.7 Atlas (C1)

Fig. 2.8 Axis (C2)

Fig. 2.9 Typical cervical vertebra (C4)

Clinical box 2.3

Injuries in the cervical spine

The cervical spine is prone to hyperextension injuries, such as “whiplash,” which can occur when the head extends back much farther than it normally would. The most common injuries of the cervical spine are fractures of the dens of the axis, traumatic spondylolisthesis (anterior slippage of a vertebral body), and atlas fractures. Patient prognosis is largely dependent on the spinal level of the injuries (see p. 42).

This patient hit the dashboard of his car while not wearing a seat belt. The resulting hyperextension caused the traumatic spondylolisthesis of C2 (axis) with fracture of the vertebral arch of C2, as well as tearing of the ligaments between C2 and C3. This injury is often referred to as “hangman’s fracture.”

Fig. 2.10 Thoracic spine
Left lateral view.

Fig. 2.11 Typical thoracic vertebra (T6)

Fig. 2.12 Lumbar spine
Left lateral view.

Clinical box 2.4

Osteoporosis

The spine is the structure most affected by degenerative diseases of the skeleton, such as arthrosis and osteoporosis. In osteoporosis, more bone material gets reabsorbed than built up, resulting in a loss of bone mass. Symptoms include compression fractures and resulting back pain.

Fig. 2.13 Typical lumbar vertebra (L4)

Fig. 2.14 Sacrum and coccyx

Fig. 2.15 Sacrum
Superior view.

Fig. 2.16 Intervertebral disk in the vertebral column
Midsagittal section of T11–T12, left lateral view. The intervertebral disks occupy the spaces between vertebrae (intervertebral joints, see p. 16).

Fig. 2.17 Structure of intervertebral disk
Anterosuperior view with the anterior half of the disk and the right half of the end plate removed. The intervertebral disk consists of an external fibrous ring (anulus fibrosus) and a gelatinous core (nucleus pulposus).

Fig. 2.18 Relation of intervertebral disk to vertebral canal
Fourth lumbar vertebra, superior view.

Fig. 2.19 Outer zone of the annulus fibrosus
Anterior view of L3–L4 with intervertebral disk.

Clinical box 2.5

Disk herniation in the lumbar spine

As the stress resistance of the anulus fibrosus declines with age, the tissue of the nucleus pulposus may protrude through weak spots under loading. If the fibrous ring of the anulus ruptures completely, the herniated material may compress the contents of the intervertebral foramen (nerve roots and blood vessels—see posterolateral herniation below). These patients often suffer from severe local back pain. Pain is also felt in the associated dermatome (see p. 42). When the motor part of the spinal nerve is affected, the muscles served by that spinal nerve will show weakening. It is an important diagnostic step to test the muscles innervated by a nerve from a certain spinal segment, as well as the sensitivity in the specific dermatome. Example: The first sacral nerve root innervates the gastrocnemius and soleus muscles; thus, standing or walking on toes can be affected (see p. 446).

Posterior herniation (A, B) In the MRI, a conspicuously herniated disk at the level of L3–L4 protrudes posteriorly (transligamentous herniation). The dural sac is deeply indented at that level. *CSF (cerebrospinal fluid).

Posterolateral herniation (C, D) A posterolateral herniation may compress the spinal nerve as it passes through the intervertebral foramen. If more medially positioned, the herniation may spare the nerve at that level but impact nerves at inferior levels.

Microdiscectomy surgery (E, F) is performed in order to remove a portion of a herniated disc that is irritating the nerve root. Through a small incision, the erector spinae muscles are reflected laterally to expose the ligamentum flavum, which is then removed in order to access the nerve roots in the spinal canal. A small portion of the facet joint may be removed to both facilitate access and relieve pressure on the nerve roots. Only the herniated portion of the disk is removed with the remaining tissue left intact.

Fig. 2.20 Zygapophyseal (intervertebral facet) joints
The orientation of the zygapophyseal joints differs between the spinal regions, influencing the degree and direction of movement.

Fig. 2.21 Uncovertebral joints
Anterior view. Uncovertebral joints form during childhood between the uncinate processes of C3–C7 and the vertebral bodies immediately superior. The joints may result from fissures in the cartilage of the disks that assume an articular character. If the fissures become complete tears, the risk of...