The spinal anatomy represents the axial skeleton of the trunk and is located posteriorly and medially. Its composition includes 33-34 vertebrae.
The spine is a long, bony articular tube that extends between the base of the skull and the bones of the pelvis. It is a resistant structure, but at the same time flexible, which supports the head and the body, keeps the trunk in an upright position, allowing at the same time its movement.
Depending on the region in which they are located, these vertebrae are: cervical, thoracic, lumbar, sacral, coccygeal.
- the cervical vertebrae are seven in number
- the thoracic vertebrae are twelve in number
- the lumbar vertebrae are five in number
- the sacral vertebrae are five in number
- the coccygeal vertebrae are four or five
To name the vertebrae, use the initial of the respective area (c for the cervical, t for the thoracic, l for the lumbar, s for the sacral) and is numbered according to their position on the spine. (L1 first vertebra of the lumbar spine, C4 fourth cervical vertebra).
CONTENT:
Vertebrae
The vertebrae are made up of: body, arch, vertebral hole.
a) The body is cylindrical and is located in the anterior part of the vertebra. He is described as having an upper face and a lower face.
b) Vertebral arch: it is located in the postero-lateral part of the vertebra and consists of the pedicle, upper and lower notch, both delimiting the intervertebral hole, transverse process, upper and lower joint process, vertebral arch blade, spinal process.
c) Vertebral hole: by overlapping all the vertebral holes, the vertebral canal is born, inside which is the spinal cord. The vertebral hole is delimited by the body and the vertebral arch.
Structural features of vertebrae
The vertebrae have certain structural features depending on the region in which they are:
1. The cervical vertebrae have a small vertebral body (the smallest compared to other vertebral segments).
- the vertebral hole has a triangular shape
- the articular process has flat articular faces
- the spinous process is short
- transverse process: it is based on the transverse hole, presents the anterior and posterior tubercle and the spinal nerve groove.
2. The thoracic vertebrae have a larger vertebral body than the cervical vertebrae and a smaller one than the lumbar vertebrae
- the vertebral hole has a cylindrical shape
- the articular process has flat articular faces
- the spinous process is long, unique
3. The lumbar vertebrae have the most voluminous vertebral body, with the appearance of a bean, having the concavity towards the posterior
- the vertebral hole has a triangular shape
- the articular process has cylindrical, superior concave and inferior convex articular faces
- the accessory process is reduced in size, before it is located the costal process which is large and represents the former lumbar ribs.
4. The sacrum is formed by welding the sacral vertebrae
- a pelvic face: you can see the welded vertebral bodies and the grooves between them called transverse lines, at the end of which are located the anterior sacral holes, which represent the place of exit of the anterior branches of the sacral nerves.
- a dorsal face at which are located the median sacral ridge, resulting from the welding of the spinous processes, the intermediate sacral ridge resulting from the welding of the articular processes, the posterior sacral holes, which represent the passage of the posterior branches of the sacral nerves and the lateral sacral ridge. welding of transverse processes.
- a base: the upper body has the vertebrae S1 which together with the body of L5 form the promontory. Also at the level of the sacral base is located the superior articular process of S1.
- a lateral part to which the articular face is described, the sacral tuberosity.
- a tip that presents posteriorly the sacral hiatus and the horns of the sacrum
- the sacral canal represents the continuation of the vertebral canal. Unlike the spinal canal, it contains terminal fillum, the structure around which the ponytail is formed by the sacral nerves.
5. The coccyx is formed by welding the coccygeal vertebrae but has small dimensions, it is rudimentary. It shows the horn of the coccyx which, through the ligaments, connects to the horn of the sacrum.
The first cervical vertebra is called an atlas and consists of two lateral masses joined by arches (anteriorly longer and posteriorly shorter).
The second cervical vertebra is called the axis. It presents the tooth of the axis, the anterior articular face and the posterior articular face over which the transverse ligament of the atlas passes.
The weak points of the spine are the intervertebral discs, a kind of elastic shock absorber formed by a pulpy and fluid core. The intervertebral discs are entirely surrounded by a fibrous ring whose role is to limit the dilation of the discs and the binding of the vertebrae between them.
The nucleus pulposus loses its flexibility over time, its volume decreases, and the discs lose their normal position.
The upper and lower faces of each vertebra are separated by intervertebral discs, which are made of cartilage and whose function is to dampen shocks and pressures. The thickness of these discs is variable depending on the region of the spine, reaching its maximum in the lumbar spine.
The vertebrae are connected to each other by ligaments (anterior, posterior, intervertebral), located along the entire length of the spine.
The spine is not straight, it has curves, due to the bipedal station:
1. In the sagittal plane:
- cervical lordosis
- thoracic kyphosis
- lumbar lordosis
- sacrococcygeal curvature
2. In frontal plane:
- thoracic scoliosis
- cervical and lumbar compensation curves with opposite direction to the first ones.
The role of the spine
- The spine has a role in supporting the head, torso and upper limbs
- Protection of the spinal cord – located in the vertebral canal, formed by joining the vertebral holes
- Transmission of the weight of the trunk to the pelvis and lower limbs (therefore the size of the vertebrae increases to the lower)