Vertebral column
Columna vertebralis
Also known as: spine, spinal column, backbone
The flexible, curved column of 33 vertebrae (26 separate bones in the adult) linked by intervertebral discs, facet joints and ligaments. It supports the head and trunk, transmits weight to the pelvis and protects the spinal cord.
Overview
The column comprises 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral and 3–5 (usually 4) coccygeal vertebrae. In the adult its length is ≈70 cm in men and ≈60 cm in women, of which the intervertebral discs contribute about a quarter. Vertebral bodies increase in size from C2 to L5/S1 as the load they bear increases, then the sacrum transfers weight laterally to the hip bones.
In the sagittal plane the adult column has four curvatures. The primary curvatures — thoracic and sacral kyphoses (concave anteriorly) — are present in the fetus. The secondary curvatures — cervical lordosis (develops ≈3–4 months as the infant holds up its head) and lumbar lordosis (≈12–18 months, with standing and walking) — are produced mainly by the wedge-shaped intervertebral discs. These curves make the column a spring, absorbing shock and keeping the centre of gravity over the feet.
The vertebrae are joined by intervertebral discs (symphyses) between the bodies and by zygapophysial (facet) joints between the articular processes, reinforced by the anterior and posterior longitudinal ligaments, ligamenta flava, interspinous, supraspinous and intertransverse ligaments. Successive vertebral foramina form the vertebral canal containing the spinal cord (which ends at ≈L1–L2 in adults), cauda equina and meninges; spinal nerves exit through the intervertebral foramina.
- Location
Midline of the back, from the skull to the coccyx.
Parts & subdivisions
- Neck; transverse foramina; atlas and axis specialised for head movement.
- Articulate with the ribs.
- Largest bodies; bear the most weight.
- Transmits weight to the pelvis.
- Rudimentary tail; pelvic floor attachment.
- 23 discs from C2–C3 to L5–S1.
- Formed by stacked vertebral foramina; contains the spinal cord, meninges and cauda equina.
Anatomy
- Arterial supply
Segmental spinal arteries from the vertebral, ascending cervical, posterior intercostal, subcostal, lumbar and lateral sacral arteries.
- Venous drainage
Internal and external vertebral venous plexuses (valveless — Batson plexus), a route for metastasis of prostate, breast and lung cancer to the vertebrae.
- Ligaments
Anterior longitudinal ligament (broad, strong; limits extension), posterior longitudinal ligament (narrow; limits flexion), ligamenta flava (elastic; between laminae), interspinous, supraspinous (ligamentum nuchae in the neck) and intertransverse ligaments.
- Development
From the sclerotomes of the somites by resegmentation; the notochord persists as the nucleus pulposus.
Function
- Supports the head and trunk and transmits body weight to the lower limbs
- Protects the spinal cord and nerve roots
- Allows flexion, extension, lateral flexion and rotation of the trunk and neck
- Absorbs shock through its curvatures and discs
- Provides attachment for ribs, back muscles and ligaments; houses red marrow
Clinical significance
Abnormal curvatures
Scoliosis (lateral curve with rotation), hyperkyphosis (e.g. osteoporotic wedge fractures, Scheuermann disease) and hyperlordosis (pregnancy, obesity).
Ankylosing spondylitis
HLA-B27-associated inflammatory spondyloarthropathy beginning at the sacroiliac joints; syndesmophytes fuse the vertebrae ("bamboo spine"), loss of lumbar lordosis and rigid kyphosis.
Lumbar puncture
Performed at L3–L4 or L4–L5 (below the conus); the iliac crests (supracristal plane) mark L4. The needle traverses skin, supraspinous and interspinous ligaments, ligamentum flavum ("pop"), epidural space, dura and arachnoid.
Mnemonics
Vertebral counts
"Breakfast at 7, lunch at 12, dinner at 5."
Compiled from standard anatomy and physiology references — see the Skeletal System sources. For education only; not medical advice.