The upper end of the spine supports the skull, the lower part is connected with the hip bone, and the middle part is attached with ribs, which serve as the back wall of the thorax, abdominal cavity and pelvic cavity. The spine has the functions of supporting trunk, protecting internal organs, protecting spinal cord and exercising. A longitudinal spinal canal is formed inside the spine from top to bottom, and there is a spinal cord in it (note: the spine is not equal to the spine or vertebrae, and the spine is composed of multiple vertebrae).
In addition to supporting and protecting functions, the spine also has flexible movement functions. Although the range of motion between two adjacent vertebrae is very small, most of the motion between vertebrae can be accumulated together, and a wide range of activities can be carried out, including flexion and extension, lateral flexion, rotation and rotation.
The degree of motion of each segment of the spine is different, which is related to the thickness of intervertebral disc and the direction of intervertebral joint. The sacrum is completely immobile, with little chest movement and more flexible neck and waist.
When people stand at attention, the vertical gravity line drawn by the body passes through the back of the cervical vertebra, the vertebral body at the 7th cervical vertebra and 1 thoracic vertebra, descends before passing through the thoracic vertebra, passes through the vertebral body at the thoracolumbar junction, passes through the back of the lumbar vertebra, passes through the 4th lumbar vertebra to the sacrum point, and then passes through the front of the sacrum and the sacroiliac joint to the lower limbs. The curvature of the spine, especially the curvature of the cervical spine and the curvature of the lumbar spine, changes with the change of gravity.
Extended data
At birth, the spine has an ossification center in the vertebral body and bilateral pedicles. One year after birth, the thoracic and lumbar vertebrae were completely fused. Cervical fusion in the second year. Sacrum fusion is late, about 7 ~ 10 years old, and it is often malfused, resulting in spina bifida. Fusion of vertebral arch and vertebral body Cervical vertebra is 3 years old, thoracic vertebra is 4 ~ 5 years old, lumbar vertebra is 6 years old, and sacral vertebra is 7 years old and beyond. The secondary ossification center only appears in adolescence.
It is a complex evolutionary process to divide and wrap the neural tube of the spine. In the development process, the developmental defects of the spine can form hemivertebra, wedge vertebra, butterfly vertebra, fusion vertebra and transitional vertebra, which is one of the common spinal deformities. The more common developmental disorder is spina bifida caused by the disorder of bilateral pedicle arrangement.
Mild spina bifida often appears on X-ray films because the posterior arch of lumbosacral vertebral body is not combined, but the spinal nerve is normal, the surface skin is normal or only depressed, or there is pigmentation and hair. It is called spina bifida occulta. In severe cases, spinal nerve, spinal membrane or spinal cord may bulge at the same time, resulting in corresponding spinal nerve dysfunction.
When the embryo 1 ~ 3 months, the length of spinal cord and spine is the same. In the later development process, the growth of the spine rapidly exceeds that of the spinal cord, resulting in the end of the spinal cord bulging in the spinal canal. At birth, its end is located at the level of waist 3 (the third lumbar vertebra, the same below), and in adulthood it is located at the lower edge of waist 1. The spinal cord membrane below waist 2 is called the terminal filament, which is still horizontally connected to the coccyx.
The result of this unbalanced growth is that the lumbosacral spinal nerve inclines from the starting point of the spinal cord to the corresponding intervertebral foramen, and the nerve below the spinal cord is cauda equina, which is called cauda equina nerve. Lumbar puncture and lipiodol angiography should be performed below this level to avoid stabbing the spinal cord.
Baidu encyclopedia-spine