Published on Feb 22, 2020 and last reviewed on Sep 20, 2022 - 4 min read
The spine is a complex structure and often people have a lot of misconceptions related to that. In this article, I have tried to simplify the structure of the spine, which will help you understand the disorders in a better way.
In a normal person, the spine starts from the base of the head to the buttocks. It runs in the midline with muscles and rib cage supporting on the sides. The spine is divided into four parts for easier understanding. All these parts show something in common. The names of these parts from head to lower down are:
So normally, when we tell the doctor that “I have cervical,” then we must understand that it is not a problem, but the name of a normal part of the spine.
This is the uppermost part of the spine. It has 7 vertebrae. In every spine, there are a certain number of vertebrae, which are bones and they are arranged like a stack. So, in the cervical spine, we have 7 vertebrae. This part of the spine has lordosis, that is, bent backward. The 1st vertebra is connected to the skull and is responsible for nodding or “yes” movement. The 2nd vertebra is connected to the first vertebra and is responsible for “no” or side to side movement. The unique feature of these two vertebrae is that these are very mobile and there is no disc between them. Almost 50 % of our head movements are because of them.
Rest 3rd, 4th, 5th, 6th vertebrae make the rest of the 50 % of movements. They all have a disc between them. Now the last, that is, the 7th vertebra is actually a transitional vertebra. That means, it is a cervical vertebra but behaves like thoracic vertebrae (explained below).
The thoracic spine has 12 vertebrae. It is present at the opposite of the chest wall. This part of the spine has kyphosis, that is, bent forward. This is the least mobile and most stable part of the spine. The reason for this is the ribs. We have 12 ribs. So, each vertebra is attached to one rib on the right and left side and in front, these ribs are attached with the sternum bone. So, it forms a strong cage, hence the mobility is very less. Only mobility happening at the thoracic spine is rotation because of which we can rotate our trunk backward while moving our lower limbs.
There are disc between each vertebra. Since this part of the spine is not much mobile, the incidences of disc prolapse or disc herniation are not very common in this part.
This part of spine is present in the lower back. It has a lot of similarities with the cervical spine. Like the cervical spine, this part of the spine has lordosis, that is, bent backward. This is again a very mobile part of the spine. Collective movements of this lumbar spine help us to bend forward and backward. The lumbar spine has 5 vertebrae. These 5 vertebrae have discs between them.
Since this is again the mobile segment of the spine, the incidence of disc prolapse is very common. The incidence is more common than the cervical spine because this is the most weight-bearing part of the spine. The cervical spine has to bear the weight of only the head, but the lumbar spine has to bear the weight of the entire upper trunk. The maximum movement is present between L4-5 and L5-S1, hence 90 % of the incidences of disc prolapse are common here.
Sacrum and Coccyx:
The sacrum and coccyx are the last part of the spine. They are actually fused to form a single part with no disc space in between. The sacrum is formed from 5 fused vertebrae and coccyx is formed from 4 fused vertebrae. They have no mobility in them. The main function is to connect the spine with our pelvis. So, they form a joint known as sacroiliac joint on right and left side. In this joint, the sacrum is the part of the spine and iliac is the part of the pelvis. Since there is no mobility, the disorders of these are very less and not commonly seen.
Now, all these vertebrae are arranged to form a canal, running from top to bottom. This canal is known as the spinal canal through which the spinal cord runs. So broadly, we can say that the function of these vertebrae or spine is to protect the spinal cord. This spinal cord is covered by bone all around. The spinal cord is the continuation of the brain itself. The actual spinal cord starts from the base of the head and runs down and finishes at the L1 vertebrae. From there, it is a continuation of the spinal cord known as cauda equina. It is not the spinal cord, but it is the collection of nerve roots. These nerve roots are responsible for nerve supply in our lower limbs and also for normal bladder and bowel functions.
The structure of the spine is like an “S,” that is, the cervical region has lordosis, the thoracic region has kyphosis, and again the lumbar region has lordosis. So, this “S” arrangement helps us to stand straight and look forward. Otherwise in animals, they have similar parts of the spine, but the curve in the overall spine is kyphosis, which does not allow them to stand straight. Due to this arrangement of the spinal cord, whenever there is prolapse of the disc backward (which is in maximum number of cases because that is the path of least resistance), then there is compression of that particular part of spinal cord and there could be pain in the supply of that nerve and numbness or weakness in motor power.
The important thing to know here is that the most common site of disc prolapse is the lower lumbar region and we have cauda equina part of spinal cord carrying nerve roots. Also, we have nerve roots in it responsible for bladder and bowel dysfunction. Hence, prolapse in that region can cause dysfunction of bladder and bowel. This is known as “red flag symptoms” and whenever you notice such symptoms then this is known as “cauda equina syndrome.” This is an emergency and it needs to be managed surgically. There is no alternative option available. Hence report to the doctor immediately.
The five parts of the spinal cord are divided into five regions. They are listed below:
The spinal cord consists of seven cervical vertebrae from C1 to C7. This part of the spine has lordosis, a backward bent at the first and second cervical vertebrae that control 50 % of the head movement. The rest of the third, fourth, fifth, and sixth cervical vertebrae make up the other 50 % of the movements. The seventh vertebrae are the transitional vertebrae since it is a cervical vertebra but behaves like thoracic vertebrae.
The spinal cord and the body's spine are divided into four regions from top to bottom: cervical, lumbar, thoracic, and areas. Damage to the nerves in the spine can result in many health conditions based on the region that is connected to the part of the body.
The vertebrates in the spine provide the bony enclosure for the individual nerves descending from the spinal cord's end. These tails of nerves are called equine. This controls the movement of the legs. The nerve from the lower spinal cord and equine controls leg sensations and movement.
The coccyx is the end of the spinal cord. It is also called the tailbone. Four fused forms of vertebrae make up this small piece of bone found at the base bottom of the spine. The pelvic muscles and the ligaments are attached to the coccyx.
The cauda equina in the lower part of the spine provides sensation to the muscles in the lower body. Spinal nerves send electrical signals between one's brain cells, the spinal cord, and the rest of the body. Electrical nerve signals help to feel sensations and to move the body.
The spinal cord is located inside the spinal column, which comprises around 33 bones called vertebrae. Five vertebrae are combined and fused to form the sacrum part, the part of the pelvis, and four smaller vertebrae are connected to form the coccyx.
The seven vertebrae that are present in the neck are called cervical vertebrae. These cervical spinal injuries usually cause loss of function in the legs and the arms that result in quadriplegia and also paralysis of the spinal cord.
The Lumbar and the cervical spines are the easily injured parts of the spinal cord. The cervical spine is easily injured because it has only lesser protection. Feeling weak or pain in the lower back region is an injured lumbar spine. Arthritis and degenerative joint diseases commonly affect the lumbar spine.
The lower back consists of five vertebrae. The discs between them cushion the bones and ligaments holding the vertebrae. The lower back has 31 nerves. Organs such as kidneys, colon, pancreas, and uterus are near the lower back.
Spinal stenosis can be felt in the lower back, causing pain and cramping in one or both legs. It happens when one stands for a long time or walks longer. Symptoms get worse when one bends forward or while sitting.
Last reviewed at:
20 Sep 2022 - 4 min read
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