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Curvature and movements of the vertebral column

The vertebral column, also known as the spine, is composed of a series of bones called vertebrae, which are stacked one upon another and interconnected by cartilaginous intervertebral discs to form a column. It forms the skeleton of the neck and back and is divided into five regions based on structure and location of the vertebrae. The alignment of the vertebrae within the vertebral column results in the formation of the four normal curvatures.

The vertebral column is largely flexible and capable of a range of motions and movements, such as flexion, extension, lateral flexion and rotation and thus, plays an important role in body posture and movement. The major functions of the vertebral column are to protect the spinal cord and spinal nerves particularly from mechanical trauma, and to support the weight of the body above the pelvis.

Key facts
Structure 33 vertebrae:
Cervical spine:
C1 - C7 (C1= atlas, C2= axis)
Thoracic spine:
T1 - T12
Lumbar spine:
L1 - L5
Sacral spine:
S1 - S5, fused into unique bone → sacrum
Coccyx:
3 - 5 fused vertebrae that form the tailbone
Shape Cervical curve (C2-T2): convex anteriorly → cervical lordotic curve
Thoracic curve (T2-T12):
concave anteriorly → thoracic kyphotic curve
Lumbar curve (T12 - sacrovertebral angle):
convex anteriorly → lumbar lordotic curve
Sacral curve (sacrovertebral articulation - coccyx):
concave anteriorly → sacral kyphotic curve
Movements Flexion, extension, lateral flexion, rotation (torsion)
Clinical significance Dorsopathies, osteoporosis, fractures, dislocations of vertebrae

This article will discuss the anatomy and function of the vertebral column as well as relevant clinical relations.

Contents
  1. Anatomy
    1. Primary curvatures
    2. Secondary curvatures
  2. Movements
  3. Clinical correlation
    1. Osteoporosis
    2. Excess thoracic kyphosis
    3. Excess lumbar lordosis
    4. Scoliosis
    5. Fractures and dislocations of the vertebrae
  4. Sources
+ Show all

Anatomy

The vertebral column is composed of 33 vertebrae separated by fibrocartilaginous intervertebral discs (IV discs) that unite to form a single unit supported by strong joints and ligaments. It extends from the base of the skull to the pelvis, with the vertebra generally increasing in size moving caudally, to support increasing amounts of the body’s weight which is ultimately transferred from the sacrum to the pelvic girdle. From here, it subsequently reduces in size towards the apex of the coccyx.

The vertebral column is grouped into five regions. Craniocaudally, these include seven cervical vertebrae between the skull and the thorax, twelve thoracic vertebrae which articulate with the ribs, five lumbar vertebrae, five fused sacral vertebrae which form the sacrum and 3-4 fused coccygeal vertebrae that form a single triangular bone called the coccyx. In the adult, the vertebral column has four normal curvatures, the cervical, thoracic, lumbar and sacral curvatures. These curvatures are more evident from a lateral view of the vertebral column. Their main function is to provide a flexible and dynamic support (shock-absorbing resilience) for the body and to protect the vertebral column from injury.

Primary curvatures

The thoracic and sacral (pelvic) curvatures are concave anteriorly and are referred to as kyphoses (singular: kyphosis). They appear during the fetal period of embryonic development, hence they are also termed primary or developmental curvatures. As a consequence of differences in height between the anterior and posterior parts of the vertebrae, the primary curvatures are preserved throughout life. It is important to note that the sacral curvature differs in males and females; the latter is less pronounced so that the coccyx protrudes less into the pelvic outlet, making it suitable for childbirth.

Secondary curvatures

The cervical and lumbar curvatures are concave posteriorly and convex anteriorly, being referred to as lordoses (singular: lordosis). These curvatures arise as a consequence of extension from the flexed fetal position. Although they begin to appear before birth, they are not apparent until later in infancy when they are accentuated by support of the head and by the adoption of an upright or erect human posture. As a result, they are termed secondary or acquired curvatures.

The cervical curvature becomes apparent when an infant begins to raise the head while prone and to maintain the head erect when sitting. The lumbar curvature becomes more evident when an infant begins to stand and walk in an upright posture. The lumbar curvature is more pronounced in females and ends at the lumbosacral angle which is formed at the junction of L5 vertebra with the sacrum. Differences in thickness between the anterior and the posterior parts of the intervertebral discs are mainly responsible for maintaining these secondary curvatures.

Think your knowledge of the bones of the body is pretty good? Test yourself with our skeletal system quizzes. 

Movements

The range of motion of the vertebral column depends on the specific region involved and the individual performing the movement. Some acrobats who start their training at a young age are capable of extraordinary movements. Although very little movement is permitted between any two adjacent vertebrae, movement of the vertebral column typically involves a number of segments acting as a unit. The summation of the relatively small movements results in a considerable range of movement of the entire vertebral column or specific regions of it.

The principal movements permitted by the vertebral column are: flexion (bending forward), extension (bending backwards), lateral flexion (bending right/left), and rotation (torsion/twisting). The thickness, compressibility and elasticity of the IV discs are features that primarily permit movements of the vertebral column. Thus, the extent to which the IV discs are deformed significantly affects the range of movements at each region. In addition to this, there are other anatomical constraints that may limit the range of motion depending on the specific region of the vertebral column. These include the:

  • Shape and orientation of the zygapophyseal (facet) joints
  • Tension of the articular capsules of the zygapophyseal (facet) joints
  • Attachment to the thoracic (rib) cage
  • Resistance of the back muscles and ligamentous complexes (such as the ligamenta flava and the posterior longitudinal ligament)
  • Surrounding soft tissue bulk

The various movements of the vertebral column are produced by the action of the back muscles, anterolateral abdominal muscles and the muscles of the neck with assistance by gravity. These movements are much easier and freer in the cervical and lumbar regions than other regions such as the thoracic region, which is relatively stable due to its attachment to the thoracic (rib) cage.

To learn more about the curvatures and movements of the vertebral column, take at the following study units:

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