The spine is one of the most important parts of the body that gives shape and structure to the body and supports it. Without a spine you would not be able to stand or hold yourself upright. The spine allows you to move freely and bend and straighten smoothly. The spine is also responsible for protecting the spinal cord; The spinal cord is a column of nerve fibers that connects the brain to other parts of the body and allows you to control your movements.

spinal cord

The spine is made up of 33 bones (including the sacrum and coccyx). There are 24 movable bones in the spine called vertebrae. Ligaments and muscles connect these bones together and form a structure called the spine. The spine can be divided into three parts, from top to bottom: Cervical Spine, Thoracic Spine and Lumbar Spine. Each of these parts is discussed in detail in the following sections.
A normal and healthy spine has an "S" shape curve where the cervical vertebrae are slightly inward, the thoracic vertebrae are slightly outward, and the lumbar vertebrae are slightly inward. In addition to helping to distribute the body weight evenly, this curvature makes the spine able to withstand any pressure. Meanwhile, although the lower part of the spine bears more weight, the performance of each part depends on the proper performance of other parts

The Cervical Spine

Cervical vertebrae include the first 7 vertebrae (C1-C7) in the spine, which begin immediately after the skull and end above the thoracic vertebrae. The spine in the cervical vertebrae, like the lumbar vertebrae, has a concave curve, which is called "lordotic curve".
The range of motion of the cervical vertebrae is much greater than other parts of the spine. To understand this, just think about all the directions and angles you can move your head and neck in. Unlike other parts of the spine, in each cervical vertebra there is a special opening for the passage of arteries that are responsible for supplying blood to the brain.

The first two cervical vertebrae are called the Atlas and the Axis, which are different from the other vertebrae because they are specifically designed for rotational movements. In fact, these two vertebrae are the cause of turning your head and neck in different directions.
The atlas vertebra (C1) is the first vertebra in the cervical spine, which is located between the skull and the rest of the spine. The atlas vertebra does not have a vertebral body, but it has a thick anterior arch, a thin posterior arch and two lateral masses.
Ace vertebra (C2) is the second vertebra in the cervical spine. Ace vertebra has an upper projection called odontoid process, which is fixed in the cavity in the atlas vertebra. With the help of the ligaments that connect the atlas and the aceta, the head allows the head to rotate to the sides as much as possible. The risk of injury in the cervical vertebrae is high because the support of the muscles in the neck area is limited and the weight bearing of the head - about 5.5 kg (12 lb) - is responsible for this part of the spine. This weight is very high for a small and narrow part like the neck, which has many soft tissues. Violent and sudden movements in this area can damage the bones, ligaments, or even the arteries that carry blood to the brain

The Thoracic Spine

The thoracic spine consists of 12 vertebrae (T1-T12) that are located between the cervical and lumbar vertebrae. The thoracic spine has a convex curve, which is called "kyphotic curve".
The range of motion of the thoracic vertebrae is more limited compared to the lumbar and cervical vertebrae, and the spinal canal is relatively smaller in this section; Because these vertebrae are connected to the ribs from the back (the back wall of the chest) and the intervertebral discs are thin in this part of the spine.

The Lumber Spine

The last group of movable vertebrae in the spine are the lumbar vertebrae, which naturally contain 5 vertebrae, but sometimes people are born with 6 vertebrae in this area. The end part of the spine, called the sacrum, consists of a special group of vertebrae that connect the spine to the pelvis. If one of the bones in this part of the spine, instead of being more like a part of the sacrum, becomes a lumbar vertebra, the sixth lumbar vertebra or transitional vertebra is formed. This event is not dangerous and does not appear to cause serious side effects.
Lumbar vertebrae, like cervical vertebrae, have a concave curve, which is called "lordotic curve". If you imagine the entire spine as an "S" shape, the lumbar region will be the bottom curve of the "S". The vertebrae in this area are larger than the other vertebrae in the spine, and for this reason, the nerve fibers in this area of the spine have more space. The spinal canal is also wider in the lumbar region than in the cervical and thoracic regions.
When people experience pain in their spine, it is often from the lumbar region. Because the lumbar vertebrae are also the place where the spine is connected to the pelvis; It means exactly where the greatest pressure due to weight is applied. The spine is the part of the spine that people put a lot of pressure on while performing movements such as lifting a heavy box, turning or carrying a heavy object

Sacroiliac Joint

There are two joints in the pelvic bone that connect the sacrum to the large pelvic bone (ilium). These two joints are called sacroiliac joints (SI joints). In these joints, where the bones join together, there are many protrusions and depressions that make them fit together like pieces of a puzzle.
Like any other joint, the surface of the sacroiliac joints is also covered with articular cartilage, but of a different kind! The articular surfaces in the sacroiliac joints are both hyaline (glassy cartilage) and fibrocartilage (spongy)

Sacroiliac joints are unique in terms of limited range of motion; For example, these joints only move 2 to 4 mm when bearing weight and bending forward. This amount of movement occurs in joints that have movements called "sliding movements"
Sacroiliac joints are viscoelastic joints; This means that most of their movement is the result of stretching. The movement of this type of joint is very different from the hinge joint such as the knee or ball and socket joint of the thigh. The main task of the sacroiliac joints is to absorb sudden shocks to the spine during stretching in different directions
Sacroiliac joints, like joints of other lower motor organs, have a "self-locking" mechanism that helps maintain stability during walking. During weight transfer from one leg to another, these joints lock on one side