Vertebral Column (Spine)
Columna Vertebralis
location_on Central axis of the body, from the skull base to the pelvis
The vertebral column is the central supporting structure of the body, consisting of 33 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused), and 4 coccygeal (usually fused). It protects the spinal cord, supports the head and trunk, allows movement in multiple planes, and transmits weight to the lower limbs. The four alternating curves (cervical lordosis, thoracic kyphosis, lumbar lordosis, sacral kyphosis) provide spring-like shock absorption.
Key Anatomical Features
- 33 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused), 3-5 coccygeal (fused)
- 24 movable vertebrae separated by 23 intervertebral discs
- Four curves: cervical and lumbar lordosis (secondary), thoracic and sacral kyphosis (primary)
- Vertebral canal encloses and protects the spinal cord and cauda equina
- Intervertebral foramina between adjacent vertebrae transmit spinal nerve roots
- Ligamentous system includes anterior and posterior longitudinal ligaments, ligamentum flavum, interspinous and supraspinous ligaments
Muscle Attachments
| Muscle | Attachment | Action |
|---|---|---|
| Erector spinae (iliocostalis, longissimus, spinalis) | Spans the entire vertebral column from sacrum to skull | Primary extensors of the spine |
| Transversospinalis group (multifidus, semispinalis, rotatores) | Transverse to spinous processes across segments | Extend and rotate individual vertebral segments |
| Psoas major | T12-L5 vertebral bodies and transverse processes | Flexes the hip and laterally flexes the lumbar spine |
| Quadratus lumborum | 12th rib to iliac crest via lumbar transverse processes | Laterally flexes the trunk and fixes the 12th rib |
| Rectus abdominis | Pubis to sternum and costal cartilages | Flexes the trunk (antagonist to erector spinae) |
| Sternocleidomastoid | Mastoid process to sternum and clavicle | Flexes the cervical spine and rotates the head |
Joints and Articulations
| Joint | Type | Connects to |
|---|---|---|
| Intervertebral disc joints | Cartilaginous symphysis (secondary) | Adjacent vertebral bodies via nucleus pulposus and annulus fibrosus |
| Zygapophyseal (facet) joints | Synovial plane | Superior and inferior articular processes of adjacent vertebrae |
| Atlanto-occipital joint | Synovial condyloid | Atlas to occipital bone (allows nodding) |
Common Pathologies
Disc herniation
Protrusion of the nucleus pulposus through the annulus fibrosus. Most common in the lumbar spine (L4-L5, L5-S1) and cervical spine (C5-C6, C6-C7). Causes radiculopathy from nerve root compression.
Scoliosis
Lateral curvature of the spine exceeding 10 degrees, measured by the Cobb angle. Adolescent idiopathic scoliosis is the most common type, predominantly affecting girls.
Spinal stenosis
Narrowing of the spinal canal or neural foramina, most common in the lumbar spine. Causes neurogenic claudication with leg pain and weakness during walking.
Vertebral compression fracture
Fracture of the vertebral body from axial loading, most common in osteoporotic elderly patients at the thoracolumbar junction. Kyphoplasty or vertebroplasty may be used for pain relief.
Clinical Relevance
The vertebral column has three key clinical levels to remember: the spinal cord ends at L1-L2 (conus medullaris), the dural sac ends at S2, and the vertebral column ends at the coccyx. Lumbar puncture is safely performed below L2 to avoid the spinal cord. The intervertebral disc has no blood supply in the adult; it receives nutrition by diffusion, which is why disc degeneration is nearly universal with aging. The facet joint orientation determines the primary motion at each spinal level: cervical facets allow flexion-extension and rotation, thoracic facets allow rotation, and lumbar facets allow flexion-extension.
Development and Ossification
Each vertebra develops from three primary ossification centers: one for the centrum (body) and one for each half of the neural arch. The centra develop from the sclerotome of somites during weeks 4-6 of embryonic development. Each definitive vertebral body forms from the lower half of one sclerotome and the upper half of the sclerotome below (resegmentation), which explains why spinal nerves exit between vertebrae.
Did You Know?
- The intervertebral discs account for about 25% of the total height of the vertebral column
- Astronauts in space can grow up to 5 cm taller due to disc expansion in the absence of gravity
- The vertebral column has a total range of motion of about 250 degrees of combined flexion-extension, lateral bending, and rotation
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