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There are 4 different types of vertebrae:
- Cervical vertebrae
- Thoracic vertebrae
- Lumbar vertebrae
- Sacrococcygeal vertebrae
As we know, our skeletal system is divided into the axial and appendicular skeleton. An important part of our axial skeleton is the vertebral column. This is the column through which our spinal cord passes – a very essential aspect of our being.
The vertebral column picks up from where the skull ends and goes right down to the lower back. It is composed of 31 individual bones called vertebrae, and the entire column is divided into 5 sections – cervical, thoracic, lumbar, sacrum and coccyx – in descending order of location. Each section has a different number of vertebrae, interspersed with intervertebral discs. These discs allow movement, act as shock absorbers, form fibrocartilaginous joints, etc. They are an important part of the vertebral column.
The typical structure of a vertebra is illustrated below:
There is a part of the body, the vertebral foramen, where the spinal cord passes through, and a number of processes exist. These processes are elongated, bony protrusions that help in articulation with muscles and other bones
These make up the first section of the vertebral column and comprise 7 bones – C1 to C7. They generally have a smaller body and larger vertebral foramen, and are known as the smallest vertebrae. Their spinous process is bifid, and the two segments are unequal. While the structure of C3 to C6 is similar, C1, C2 and C7 are slightly different, modified for specific functions. C1 is called the atlas. It has this name because it bears the skull, considered the “globe” of the body. The atlas lacks a body and is a ring-like structure. It has a wide vertebral foramen to accommodate the thick part of the spinal cord.
Below this is the C2, called the axis. This acts as a pivot upon which the atlas rotates. The most noticeable part of this bone is the odontoid process, which rises perpendicularly. It is this part that breaks during a ‘judicial hanging’ and hits the medulla, causing death. C7 is also called vertebra prominens. If you touch the nape of your neck, a bony protrusion can be felt. This is the spinous process of the vertebra prominens. The spinous process of C7 is not bifid.
The thoracic vertebrae are 12 in number and are referred to as T1 – T12. When you think of the thoracic region, the first thing that comes to mind is the rib cage. The rib cage lies in the thoracic region of the body, and the thoracic vertebrae have a slight modification to articulate with the ribs. This modification comes in the forms of demifacets. Facets are basically flattened surfaces of a bone. A demifacet is half of a facet, and is meant for articulation with the ribs and coastal cartilage. The vertebrae have both superior and inferior demifacets. Each rib articulates with the corresponding vertebra and the vertebra above it.
There are five lumbar vertebrae, designated as L1 – L5. These are the largest vertebrae and have huge bodies. They take on the weight of the body and have a great capacity for movement. The orientation of their process is parasagittal, which is supposedly responsible for their capacity for bending. Spondylosis is most common is this region of the vertebral column.
More often than not, the sacrum and coccyx are studied together as the sacrococcygeal region. The sacrum consists of 5 bones that fuse together to form a single bone, while the coccyx consists of 3-5 bones that typically do the same. In females, the sacrum is short and wide, whereas in males it is long and narrow. The coccyx is the remnant of the tail.
Damage to the vertebral column can become extremely dangerous as it houses the spinal cord. Therefore, one must be careful of even tiny things, such as your position while sitting, lifting weights, etc. Life would not be the same – nor possible – without a strong and stable spinal cord, so do whatever you can to keep it safe!