Bones of Spine

Our spine has 26 vertebrae, but actually, there are 33 vertebrae in total but the five sacral and four coccygeal vertebrae are fused together. So they are considered as one each. The upper 24 vertebrae are separated from each other by an intervertebral disc between them. And those 24 vertebrae are movable and the remaining are fused together. Vertebrae of different regions have different structures and functions. 

Human Spine Anatomy 

Usually, the human spine anatomy is described by dividing it into three major parts: cervical, thoracic, and lumbar spine. And the bone below the lumbar spine is called the sacrum. Each part of the spine is made up of an individual bone called vertebrae, there are 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae. There are four facet joints associated with each vertebra, one pair faces upward and the other pair faces downward. They interlock with the adjacent vertebrae and provide stability to the spine.

The upper and lower portion of the vertebral body is filled with hyaline cartilage. The adjacent vertebral bodies are separated by a fibrocartilaginous intervertebral disc.

These discs are made of two parts. The hard and tough outer layer is called the annulus and the surrounding mushy, moist center is known as the nucleus. 

The spine is mainly divided into five segments. The bones of the spine are named according to their location like cervical vertebrae are named as C1, C2, C3, etc. The bone of the thoracic region is named T1, T2, T3, etc, and the lumbar region bone is named L1, L2, L3, etc. 

• Cervical - 

The first 7 vertebrae from C1 to C7 is known as the cervical region. The first vertebra C1 or atlas articulates with the two occipital condyles of the skull allows the maximum movement of the neck. C1 is responsible for the yes movement of the head. And C1 and C2 are responsible for ‘no’ movement of the head. 

• Thoracic - 

After the cervical bone 12 vertebrae from T1 to T12 are known as the thoracic region. It has limited motion and it provides support to the rib cage and protects the lungs and the heart. There are 12 pairs of rib bones that articulate with the thoracic vertebrae on the posterior side.

• Lumbar- 

This is the last region having five vertebrae L1 to L5, It supports the weight of the body. Actually, they are large in size and help to carry heavyweight objects.  

Spine Bone Structure 

All spine bones share a common basic structure, consisting of the anterior vertebral body and the posterior vertebral arch. 

Anterior Vertebral Body - 

It forms the interior part of each vertebrae. It is a weight carrier, and the vertebrae in the lower part of the column have larger bodies than those in the upper portion (to provide better support for increased weight). 

Vertebral Arch - 

It forms the lateral and posterior aspects of each vertebra. The verbal arch combines with the vertebral arch to form an enclosed hole known as the vertebral foramen. The foramina of all the vertebrae make up a line to form the vertebral canal, which encloses the spine.

The vertebral arch has several bone positions,  which serve as areas of attachment of muscles and tendons:

• Spinous Processes - 

In this process, each vertebra has a single spinous process, centered posteriorly behind the arch point.

• Transverse Processes - 

In this process, each vertebrae has two transverse processes. In which one extends laterally and the other posteriorly from the vertebral body and in the thoracic vertebrae, the transverse processes articulate with the ribs. 

• Pedicles – 

It connects the vertebral body to the transverse processes.

• Lamina – 

It connects the transverse and spinous processes.

• Articular Processes - 

It forms a joint between one vertebrae and its superior and inferior counterparts and they are located in the intersection of laminae and pedicles. 

How many Bones in the Spine are There?

The number of bones in the spine is 26 also known as the vertebral column. The vertebral column is part of the axial bones, consisting of the skull, ribs, and sternum outside the vertebral column. The existing notochord in the embryonic phase has been replaced by the vertebral column. The spine forms the main structure of the stem. It is placed inside and attached to the bottom of the skull. Each vertebra has an empty central part, forming a neural canal through which the spine passes and the spine protects the spinal cord.

Conclusion

After going through complete information about bones of the spine, we get to know how many bones in the spine? different types of bones in the spine. And some of the important roles performed by different regions of the spine. We also got to know about different processes like spinous processes, transverse processes, and articular processes.