The spine allows us to stay upright in three-dimensional space and houses the spinal cord, a component of the central nervous system. We tell you its particularities.
The spine, formed from bone segments, fascia and mobile muscles, is considered a true work of art as far as biomechanics are concerned. Its main function in vertebrates is to allow the maintenance of the static and dynamic support in a three-dimensional space, in addition to helping us maintain the center of gravity.
Biomechanics is responsible for studying structures as sophisticated as this, a science that investigates the action of both internal and external forces and their impact on the human body, both in anatomy and functionality. Its main task is to show us how each bone and shape of our body has a useful, invaluable and irreplaceable function.
Today we come to unravel the very secret of movement and permanence in a three-dimensional space because, without the backbone, life would not be conceived beyond anevolutionarily simple sack of flesh. Do not miss it, because this structure keeps many more secrets than it may seem at first.
- We recommend you read:”Meninges: anatomy, characteristics and functions”
What is the spine?
According to the National Cancer Institute (NIH), the spine is defined as theset of bones, muscles, tendons, and other tissues that run from the base of the skull to the coccyx. In addition to supposing a physiological structure of support by itself, it is also essential for nerve transmission, because inside it is protected the spinal cord, responsible for transmitting information to the 31 pairs of spinal nerves that communicate our body.
Among many other things, we can start by saying that the spine has certain basic functions. These are as follows:
- Keep the trunk upright: it is a supporting structure that, with the help of muscular and ligamentous support, stabilizes the trunk against the force of gravity.
- Allow the movement of the trunk: as the vertebrae are articulated, our trunk movement is not compromised.
- Serve as an anchor point to muscles and organs, both internal and external.
- Protect the spinal cord, our most important nerve center along with the brain.
- Serve as an anchor point for the skull, where our senses are centralized and the perception of the environment occurs in humans.
Parts of the spine
The spine extends from the skull to the pelvis andis made up of 33 individual bones, known as vertebrae, plus 120 muscles, as well as 100 joints and 220 individual ligaments. These bony structures are stacked on top of each other in 5 regions: cervical, thoracic, lumbar, sacral and coccyx. We will explain the particularities of each of these sections in more detail.
1. Cervical region
The cervical vertebrae are those thatare located in the neck and allow us to move our head, neither more nor less. They are located between the skull (the bone box that contains the brain and protects it from blows) and the thoracic vertebrae, they are 7 and are known as C + the corresponding number (C1, C2, C3, etc). The curvature formed by the arrangement of these vertebrae is known as lordosis.
Especially important is the C1 vertebra, known as the atlas. This, when articulating on the occipital bone, supports the head, hence its imposing name (in Greek mythology, Atlas was a titan that held the weight of heaven on his shoulders). Axis, the second cervical vertebra C2, also has a name and characteristics of its own.
2. Thoracic region
The 12 thoracic vertebrae (T1-T12) are the very base of the spine, each being more voluminous than the previous one, until it meets the lumbar region. These vertebrae are characterized by the presence of pedicles, pillars present on each side of the vertebral body.
The 12 vertebrae of the dorsal region draw a curvature, called dorsal kyphosis. Congenital pathologies related to the back, such as scoliosis, cause imbalances in the form of kyphosis. It is estimated that up to 7,000,000 American patients have some form of scoliosis.
3. Lumbar region
As surprising as it may seem, these 5 vertebrae (L1-L5) cause many problems in normal life. This is because, mainly, the lumbar vertebraeare the ones that carry most of the body weightand all the biomechanical stress associated with daily efforts and activities.
Pain in the lumbar vertebrae has an incidence of 60-90%, which means that up to 9 out of 10 people will have it at some point in their lives. 80% of these pains are acute, that is, transient, while 20% become chronic and can occur permanently, unfortunately.
This section presents another curvature, also called lordosis, such as the one we have mentioned in the cervical region. In the lumbar vertebrae, the pedicles are longer and wider, as each of these bones supports much more weight than those previously mentioned. These 3 regions (cervical+thoracic+lumbar) add up to a total of 24 vertebrae, all of them mobile.
4. Región sacra
La palabra “sacro” tiene dos connotaciones, derivadas de lenguas diferentes. En griego este término proviene de la fusión de ieron osteon, que significa fuerte, robusto. Por otro lado, en latín se deriva de ieratikon, que significa sagrado, especialmente al ser una de las secciones corporales ofrecidas como ofrendas a los dioses. Con esta información, ya podemos imaginar un poco la funcionalidad de la región sacra.
A partir de aquí ya hablamos de vértebras inmóviles y fijas que, en este caso, se encuentran fusionadas, formando el hueso conocido como “sacro”. Esta estructura ósea se localiza en la región pélvica y cumple diversas funciones. Entre ellas, encontramos las siguientes:
- Participa en la articulación sacroilíaca. Por tanto, interviene en los movimientos de nutación y contranutación, esenciales para el proceso del parto.
- It is essential in the creation of the spine and pelvis.
- It receives multiple muscles and ligaments, which lean on it.
- It participates in essential mechanical activities in the human being, such as walking and running.
One of the most common pathologies affecting this region is sacroiliitis, an inflammation of the sacroiliac structure, with many possible causes. One of the most common is overload during work or certain congenital asymmetries, such as one leg being higher than the other, for example.
5. Coccyx region
The coccyx represents the final part of the spine, with 3 small vertebrae usually (between 3 and 5) fused. It is a vestigial structure in humans because, in other mammals and birds, it is the insertion point or the base of the tail. The coccyx, like the rest of bone tissues, can present pathologies such as trauma, pain, cysts, infections and tumors, although it rarely fractures as such.
Some final facts about the spine
Not everything has to be anatomy in learning and, therefore, we take advantage of these final lines to show you some very curious characteristics of the spine.
For example, we can tell you that thespine measures on average about 75 centimeters, but that the intervertebral discs that separate each vertebra accumulate 1/4 of this total length. With age, these discs become damaged and dehydrated, which is why they decrease in size, partly causing that “shrinkage” effect that we humans suffer as we age.
In addition, although we have 33 total vertebrae and the final vertebrae are fused, there is a procedure that seeks exactly that: merge free vertebrae. This is done in order to solve problems such as herniated discs, instabilities and spinal deformities. This is a fascinating surgical procedure, at least from a medical point of view.
Summary
From the titan that houses the weight of the sky on its shoulders to the tail of a horse, a series of bones, called vertebrae, are “stacked”, which allow vertebrates to keep us on our limbs and perform the vital functions that characterize us. In the spine rests, neither more nor less, than the very secret of the evolution of living beings.
We have told you some of the general features that define this incredible structure but, as we said at the beginning, it is a true masterpiece of biomechanics, unfathomable in a few words. We encourage you to read more about it if you have been curious, and we give you some examples to consult in the bibliography.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.