In addition to the strength provided by the spinal joints and ligaments, significant support is provided to the spine by the surrounding paraspinal musculature, as well as muscles of the posterior and anterior abdominal walls. Ligamentum flava (yellow ligaments) connect adjacent lamina, strong supraspinous and weaker interspinous ligaments connect adjacent spinous processes, whilst thin intertransverse ligaments join adjacent transverse processes (Figure 1.4). Various ligaments provide support by connecting adjacent components of the vertebral arches. Lateral flexion, or abduction, is also possible in the human lumbar spine(1). Typically lumbar facet joints lie in an antero-posterior direction, which allows for freedom of flexion and extension, but limits rotation. The orientation of the facet joints dictates the movement which is able to occur in the lumbar spine. The anterior longitudinal and posterior longitudinal ligaments provide additional support to these vertebral body-disc spinal units.Īdjacent articular processes (superior and inferior) are joined to their companions via synovial facet joints. Contained within the annulus is the central hydrated gelatinous core, the nucleus pulposus.
The annulus fibrosis forms a peripheral ring of fibrous tissue, which connects adjacent endplates. Upper and lower surfaces of adjacent vertebral bodies are covered with a thin layer of hyaline cartilage, which forms the endplates. A typical intervertebral disc consists of three parts, each essential to the normal functioning of the disc cartilaginous endplates (CEP), annulus fibrosis (AF) and nucleus pulposus (NP). Lumbar vertebral bodies increase in size from superiorly to inferiorly and are generally kidney shaped(1).Īdjacent vertebral bodies articulate between their bodies via intervertebral discs and between their arches at the facet (zygopophyseal) joints. Where the lamina and pedicle meet, superior and inferior articular processes are present, which form synovial joints (facet joints) with matching processes of adjacent vertebrae.
Adjacent pedicles together form intervertebral foraminae for exiting spinal nerve roots. The lamina is the part of the neural arch between the transverse and spinous process, whilst the pedicle is that part of the arch anterior to the transverse process, which connects the arch to the vertebral body. From either side of the vertebral arch bony transverse processes emerge at the side (laterally), whilst a single midline bony spinous process emerges posteriorly. Located between theses two parts is the vertebral foramen, which encases the neural elements spinal cord or cauda equina (nerve roots) depending on the spinal level. Image source Dr David Oehme 2013.Ī typical vertebra consists of an vertebral body at the front (anterior) and a vertebral (neural) arch at the back (posterior). Nerve roots (yellow) are exiting through intervertebral foraminae.
Figure 2 shows a side view of human lumbar spine demonstrating five lumbar vertebrae (L1 – L5) and intervening intervertebral discs. The lumbar spine possesses an anterior convexity, or lordosis and, as in the cervical and thoracic regions, individual vertebral bodies are separated by the cartilaginous, load-absorbing intervertebral discs. The human lumbar spine typically consists of five vertebral bodies, L1 through to L5, which join with the pelvis via the sacrum at S1, and with the thoracic spine at the thoracolumbar junction (T12). Integrity of the human spine is necessary for upright posture and propulsion, as well as for movements of both upper and lower limbs(1). The complex structure of the spine allows for significant strength as well as great flexibility, whilst also providing protection to the fragile spinal cord and exiting nerves. Intervertebral discs, the shock absorbers between adjacent vertebral bodies, are shown (yellow). The cervical and lumbar regions possess a forward convexity (lordosis) whilst the thoracic and sacral regions demonstrate a forward concavity (kyphosis). Figure 1 shows a human spinal skeleton demonstrating cervical (yellow), thoracic (green), lumbar (pink) and saccro-coccygeal (blue) regions.
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