The human vertebral column is a complex structure consisting of a series of approximately 33 bones called vertebrae. These vertebrae are separated by intervertebral discs, and can be divided into five distinct regions, each characterised by a different vertebral structure. In this article, we will explore the anatomy of the vertebral column, discussing its function, structure, and clinical significance.
The vertebral column has four key functions:
Each vertebrae shares a common structure, comprising of an anterior vertebral body and a posterior vertebral arch. The vertebral body is the weight-bearing component of the vertebrae, and the vertebrae of the lower portion of the column have larger bodies than those of the upper portion to better support the increased weight. The superior and inferior aspects of the vertebral body are lined with hyaline cartilage and are separated from adjacent vertebral bodies by a fibrocartilaginous intervertebral disc.
The vertebral arches form the lateral and posterior aspect of each vertebrae, and are joined with the vertebral body to form a vertebral foramen. This is an enclosed hole which, when all vertebrae are aligned, forms the vertebral canal which encloses the spinal cord. The vertebral arches have several bony prominences which act as attachment sites for muscles and ligaments, including spinous processes, transverse processes, pedicles, laminae, and articular processes.
The intervertebral discs are fibrocartilaginous cylinders that join the vertebrae together, permitting the flexibility of the spine, as well as acting as shock absorbers. They are wedge – shaped in the lumbar and thoracic regions, and support the curvature of the spine. The discs have two main components; the nucleus pulposus and annulus fibrosus, the former being a jelly-like substance and the latter being a tough collagenous case.
Herniation of an intervertebral disc occurs when the nucleus pulposus ruptures and breaks through the annulus fibrosus. This usually occurs in a posterior-lateral direction, after which the nucleus pulposis can irritate nearby spinal nerves, resulting in a variety of neurological and muscular symptoms.
The human body has seven cervical vertebrae, which are characterised by their bifid spinous process (except for C1 which has no spinous process, and C7 which has a longer spinous process that may not bifurcate). The cervical vertebrae have three main distinguishing features: bifid spinous process, transverse processes, and pedicles. The transverse processes articulate with the rib in the thoracic vertebrae.
The twelve Thoracic vertebrae are medium-sized and increase in size as they descend. Their specialised function is to articulate with the ribs and produce a bony thorax. They have transverse processes and costal facets, which are used to articulate with the shaft of a single rib.
The five lumbar vertebrae are the largest in the vertebral column and are structurally specialised to support the weight of the torso. The lumbar vertebrae are also unique in that they cannot articulate with the rib cage in the same way as the thoracic vertebrae.
The Sacrum and Coccyx are the two fused vertebrae which make up the end of the column. The sacrum consists of five fused vertebrae and forms the posterior wall of the pelvis, while the Coccyx or tailbone is composed of four fused vertebrae.
The vertebral column provides protection, support, and axis for movement, and is composed of seven regions, each being characterised by distinctive features. These regions are the Cervical vertebrae, Thoracic vertebrae, Lumbar vertebrae, Sacrum and Coccyx, with two cervical vertebrae being unique; C1 and C2, which are specially modified to provide for head movement.
The vertebral column is an anatomical structure composed of 33 bones called vertebrae, which are connected together through intervertebral discs. It provides protection of the spinal cord within the spinal canal, and also serves to support the body above the pelvis, form the central axis of the body, and enable postural and movement functions. Structure of a vertebrae consists of an anterior vertebral body and a posterior vertebral arch, with the vertebral body being the weight-bearing component and the vertebral arch enclosing the vertebral foramen. Adjacent vertebrae are separated by fibrocartilaginous intervertebral discs, and the vertebral foramen of each vertebra line up to form the vertebral canal. The vertebral arch bony prominences, including spinous processes, transverse processes, pedicles, laminas, and articular processes, anchor muscles and ligaments.
The vertebral column can be divided into five regions: cervical, thoracic, lumbar, sacrum, and coccyx. Cervical vertebrae are unique because vertebrae C1 and C2 (atlas and axis, respectively) differ in structure from the rest, and are specialized for head movement. Thoracic vertebrae are medium sized and increase in size from superior to inferior, and contain two demi facets which articulate with two heads of ribs, and one costal facet to articulate with the shaft of a single rib. The lumbar vertebrae are the largest and are structurally specialized to support the weight of the torso. They have very large vertebral bodies, lack the characteristic features of other vertebrae such as transverse foramina, and have a triangular vertebral foramen. The sacrum is a collection of five fused vertebrae and articulates with the pelvis at the sacroiliac joints. The coccyx is a small bone and articulates with the sacrum, and is recognised by its lack of vertebral arches.
Joints and ligaments between mobile vertebrae permit some movement. The vertebral body joints are cartilaginous and articulations between articular facets are strengthened by ligaments such as the ligamentum flavum and intertransverse ligaments. The vertebral body joints are also strengthened by the anterior and posterior longitudinal ligaments, which run the length of the vertebral column. Abnormal morphology of the spine can have clinical relevance, such as in scoliosis.
Clinical relevance is linked to the intervertebral discs, which assists in the movement of the vertebral column, as well as in shock absorbance. When the nucleus pulposus ruptures, it breaks through the annulus fibrosus and usually occurs in a posterior-lateral direction. This breakage can irritate nearby spinal nerves and result in a variety of neurological and muscular symptoms, an example being intervertebrate disc herniation.
Overall, the vertebral column serves a variety of functions related to protection, support, axis formation, and movement. It is divided into five regions, with the cervical vertebrae being unique because vertebrae C1 and C2 differ in structure from the rest, while thoracic vertebrae are medium sized and increase in size from superior to inferior, and contain two demi facets and one costal facet. The lumbar vertebrae are the largest and are specialized to support the weight of the torso, while the sacrum is a collection of five fused vertebrae and the coccyx is a small bone that articulates with the sacrum. Joints and ligaments between mobile vertebrae permit some movement, and abnormal morphology of the spine can have clinical relevance. Additionally, the intervertebral discs are important clinically as they assist in the movement of the vertebral column as well as in shock absorbance. When the nucleus pulposis ruptures, it can irritate nearby spinal nerves and cause a variety of neurological and muscular symptoms.
The coccyx articulates with the apex of the sacrum and is distinguished from the other vertebrae by its lack of vertebral arches. The mobile vertebrae are connected to each other by joints between their bodies and articular facets, which are specialized cartilaginous joints that are further stabilized by the ligamentum flavum, interspinous, and supraspinous ligaments. Additionally, the vertebral body joints are connected by the intervertebral disc and reinforced by the anterior and posterior longitudinal ligaments.
The vertebral column has many important functions: it provides a protective bony cover for the delicate spinal cord; it serves as a point of attachment for the muscles of the back and limbs; it supports the body's weight; and it forms an axis of movement in the spine. Each vertebra consists of a vertebral body, a vertebral arch, and several processes which help to connect the vertebrae to each other. The vertebral arch encloses the vertebral foramen, which is the canal through which the spinal cord passes. The intervertebral discs serve to separate adjacent vertebrae and absorb shocks. However, if a disc becomes herniated, it can compress the exiting nerve and cause pain.
Certain clinical syndromes are directly linked to the abnormal curvature of the spine. This includes kyphosis, which is an abnormally increased curvature of the thoracic spinal column; lordosis, which is an abnormally increased curvature of the lumbar spinal column; scoliosis, which is an exaggerated lateral curvature of the spine; and cervical spondylosis, which is a degenerative condition of the cervical spine that results in neck pain and stiffness.
