As the proverbial backbone, the spine gives the body shape and stability. Its specific shape enables humans to walk upright.
What is the spine?
Defining the spine as the axial skeleton of the human body shows that it serves as the central connecting and supporting element between the skull, ribs, pelvis and extremities. It is a construction of 24 vertebrae (vertebrae) and 23 cartilaginous connections (synchondroses), which is additionally stabilized by a ligamentous and muscular apparatus.
Anatomy and structure
Schematic anatomical representation of the spine and its structure. The spine shows a complex anatomical structure. A vertebra consists of vertebral body (corpus vertebrae), vertebral arch (arcus vertebrae), and vertebral arch processes (processus arcus vertebrae). The vertebral bodies transfer the load of the upper body to the pelvis, which is why their size increases steadily from top to bottom. A vertebral arch is a bony clasp at the back of the vertebra that encloses the vertebral hole in a horseshoe shape. The vertebral holes of all vertebrae together form the spinal canal, which contains the spinal cord. Seven processes are located at each vertebral arch. Visible and palpable from the outside are the spinous processes (processus spinosi), which project backward. Two transverse processes (processus transversi) point to the right and left. Ligaments and muscles are attached to the spinous and transverse processes. Two upper and two lower articular processes (Processus articulares superiores et inferiores) serve as connecting surfaces between the individual vertebrae. The spine is divided into five sections: seven cervical vertebrae form the cervical spine, the thoracic spine consists of twelve thoracic vertebrae and the lumbar spine consists of five lumbar vertebrae. Downward is the sacrum, whose five sacral vertebrae are fused together. The coccyx below consists of four to five rudimentary coccygeal vertebrae. Between the vertebrae are the intervertebral discs (Disci intervertebrales), which have an outer ring of fibrocartilage and a gelatinous core. Their structure makes them physiological shock absorbers. However, the double S-shaped curvature of the spine is the main factor that contributes to the cushioning of impacts during walking and thus to the protection of the brain. The cervical and lumbar spine are convexly curved forward (lordosis), while the thoracic spine is curved backward (kyphosis).
Functions and tasks
The function and tasks of the spine are diverse and of central importance. It represents a compromise between stability and mobility. Functionally, the spine can be divided into so-called motion segments. This means two adjacent vertebrae each with intervertebral disc, vertebral arch joints and all connecting ligamentous and muscular structures. Movements are possible around three axes, namely flexion to the front or extension to the back, inclination to the side (lateral flexion) and rotation around the vertical axis. The degree of mobility varies in the individual spinal segments. For example, the cervical spine is most mobile in all three axes. Despite the high number of vertebrae, the thoracic spine is the most immobile section because it is firmly bound into the thorax. In the lumbar spine, rotation in particular is very limited.
Diseases
By the age of fifty, more than 70% of the population experiences persistent or episodic diseases and discomfort in the spine, caused by incorrect or excessive loading, as well as degenerative or inflammatory processes. A common cause of back pain is scoliosis, which is a lateral curvature of the spine. A curvature of up to ten degrees is physiological; beyond that, complaints can extend to thoracic deformities with impaired heart and lung function. Another well-known complaint is the herniated disc or disc prolapse. In this case, parts of the intervertebral disc are pressed into the spinal canal due to incorrect loading and painfully constrict the spinal nerve running there. Sensory and motor deficits may also occur. As a reaction, the back muscles on the opposite side often cramp and the patient experiences “lumbago“. With increasing age, osteoporosis often occurs, especially in women. This is a pathological bone loss due to demineralization, which reduces the load-bearing capacity of the spine.This or particularly severe trauma can cause vertebral fractures, which in the worst case can damage the spinal cord and lead to paraplegia. Last but not least, calcifications, such as in rheumatoid inflammatory ankylosing spondylitis, can immobilize the spine.
Typical and common diseases
- Spinal curvature
- Spinal injury (spinal trauma)
- Vertebral body fracture (vertebral body fracture)
- Vertebral joint arthritis
