Vertebral column (Spine)

Summary

The vertebral column extends from the skull to the pelvis and consists of 33 vertebrae, which are differentiated into five regions: the cervical spine (C1–C7), the thoracic spine (T1–T12), the lumbar spine (L1–L5), the sacrum (S1–S5; fused in adults), and the coccyx (3–5 fused bones). The functions of the vertebral column include protecting the spinal cord within the vertebral canal; transferring the weight of the upper body to the pelvis; articulating with the skull, ribs, and pelvis; and providing attachment for musculature. It is, furthermore, the main site of hematopoiesis besides the pelvis. The basic vertebra consists of a vertebral body (anterior), a vertebral arch (posterior), and a vertebral foramen, through which runs the spinal cord. More specific morphological features vary according to the region and associated function. Adjacent vertebrae articulate via intervertebral discs and facet joints, and there are specialized joints in the upper cervical region, the thoracic region, and between the sacrum and pelvis for articulation with the head and neck, the ribs, and the hip respectively. Embryologically, the vertebrae are derived from the somites of the paraxial mesoderm, and the nucleus pulposus of the intervertebral discs is derived from the notochord.

Gross anatomy

Overview [1][2]

  • Characteristics
    • The vertebral column consists of 33 vertebrae.
    • Differentiated into cervical, thoracic, lumbar, sacral, and coccygeal region
    • Has a double-S shape.
      • Curves convex anteriorly in the cervical and lumbar regions (lordosis)
      • Curves convex posteriorly in the thoracic and sacral regions (kyphosis)
  • Function
Spinal segment Number of vertebrae Short term Curvature
Cervical spine 7 C1–C7 Lordosis
Thoracic spine 12 T1–T12 Kyphosis
Lumbar spine 5 L1–L5 Lordosis
Sacrum 5 (fused) S1–S5 Kyphosis
Coccyx 3–5 (fused) - -

Vertebrae [1][2]

Basic vertebral structure

The basic vertebra consists of a vertebral body anteriorly and vertebral arch posteriorly, which together surround the vertebral foramen.

Vertebral body

Vertebral arch

Consists of two pedicles (laterally) and two laminae (posteriorly) with several processes

Vertebral foramen

Specific vertebrae

Specific vertebra levels are associated with key anatomical landmarks: e.g., C4 (bifurcation of common carotid artery), T2 (aortic arch), T4 (bifurcation of trachea), L1 (end of spinal cord in adults), L3 (end of spinal cord in newborns), and L4 (level of iliac crest; bifurcation of aorta).

Joints of the spine [1][2]

Atlanto-axial instability is the loss of ligamentous stability between atlas (C1) and axis (C2), which may cause the odontoid process to compress the spinal cord, medulla, or vertebral arteries when the neck is flexed. It is most commonly caused by Down syndrome, rheumatoid arthritis, or trauma! [3]

Degeneration of the intervertebral discs with age is common and may lead to back pain, radiculopathy, or cauda equina syndrome!

Ligaments of the spine

Anatomy Function
Anterior longitudinal ligament
  • Limits extension of the vertebral column
  • Supports the anterior annulus fibrosus
Posterior longitudinal ligament
  • Limits flexion of the vertebral column
Ligamenta flava
  • Support upright posture
Nuchal ligament
  • Formed of tendons and fascia of the posterior neck muscles
  • Runs from the external occipital protuberance and atlas to the spinous processes of the cervical vertebrae, ending at C7
  • Triangular in shape in the sagittal plane
Supraspinous ligament
  • Limits flexion of the vertebral column
Interspinous ligaments
  • Limits flexion of the vertebral column
Intertransverse ligaments
  • Limit lateral flexion of the vertebral column

The narrowing of the posterior longitudinal ligament leaves the annulus fibrosus without support in the posterolateral region, increasing the likelihood of disc herniations in this region, which may cause compression of the spinal nerve at the level below (e.g., herniation of the L4/5 disc compresses the L5 nerve)!

In ankylosing spondylitis, calcification of the spinal ligaments and intervertebral discs causes fusion and immobility of the spine!

During lumbar puncture, the needle pierces the following structures in order before it reaches the subarachnoid space: skin, subcutaneous tissue, supraspinal ligament, interspinal ligament, ligamentum flavum, epidural space, dura mater, and arachnoid mater.

Muscles

Vasculature and lymphatics

Arteries Veins Lymphatics
Cervical vertebrae
  • Valveless venous plexuses outside and within the vertebral canal (in the epidural space) along the entire vertebral column
  • Communicate with veins of the prostatic venous plexus via Batson plexus and with the dural venous sinuses
  • Drain into the vertebral veins, venae cavae, azygous veins, and deep veins of the pelvis
  • Drain to deep cervical nodes
Thoracic vertebrae
  • Posterior intercostal arteries (from aorta)
  • Drain to intercostal nodes
Lumbar vertebrae
  • Drain to para-aortic nodes
Sacrum
  • Drain to lateral sacral and internal iliac nodes
Coccyx

The lack of valves of the venous plexuses facilitates spread of malignant cells (e.g., from prostate cancer) and bacteria in the bloodstream to the vertebrae, leading to metastases and osteomyelitis.

Innervation

Microscopic anatomy

See bone tissue, bone marrow, and connective tissue.

Embryology and development

The vertebral column is derived from the somites of the paraxial mesoderm and begins developing in the 4th week.

Clinical significance

  • 1. Standring S. Gray's Anatomy: The Anatomical Basis of Clinical Practice. Elsevier Health Sciences; 2016.
  • 2. Ellis H, Mahadevan V. Clinical Anatomy. Wiley-Blackwell; 2018.
  • 3. Fleisher LA, Cohen NH, Wiener-Kronish JP, Young WL. Miller's Anesthesia. Saunders; 2014.
last updated 06/13/2019
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