Bones of Spine - Anatomy, Structure, Number of Bones in Spine

Bones of Spine: The spine, also known as the backbone, is a bony structure that supports the body and connects various parts of the musculoskeletal system, which includes bones and muscles. It allows you to sit, stand, walk, twist, and bend. The vertebral column, or spinal column, is made up of 33 vertebrae separated by spongy disks and divided into four distinct regions.

The cervical region, located in the neck, has 7 vertebrae, with the first one supporting the skull. The thoracic region consists of 12 vertebrae in the upper back. The lumbar region contains 5 vertebrae in the lower back. Additionally, there are 5 sacral vertebrae and 4 coccygeal vertebrae, although the number of coccygeal vertebrae can vary from 3 to 5.

The disks between each vertebra help absorb shock. By adulthood, the 5 sacral vertebrae fuse into a single bone, and the 4 coccygeal vertebrae fuse into one bone.

The spinal cord, a bundle of nerves, runs through the center of the vertebral column. The spine protects the spinal cord and allows nerves to connect to the arms, legs, and organs at each level. NEET Biology Notes on Bones of Spine are provided in the article below.

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What is Spine in Human Body?

The human spine, also known as the vertebral column, is a important part of the skeletal system, providing both support and flexibility to the body. It consists of 33 vertebrae, categorized into five regions: cervical, thoracic, lumbar, sacral, and coccygeal, each with specific functions. The cervical spine supports and enables the movement of the head, the thoracic spine secures the rib cage and safeguards the heart and lungs, the lumbar spine bears the body's weight and allows for movement, and the sacral and coccygeal regions stabilize the pelvis and aid in sitting.

Intervertebral discs between the vertebrae act as cushions and absorb shocks, while the spinal canal protects the vital spinal cord. This complex structure is essential for maintaining upright posture, enabling movement, and protecting important neural pathways.

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Spine or Vertebral Column Anatomy

The vertebral column, commonly called the spine or backbone, is a vital structure that supports and protects the spinal cord while enabling flexibility and movement. Here is a brief summary:

• Cervical: The neck area, consisting of 7 vertebrae (C1-C7).
• Thoracic: The upper back, with 12 vertebrae (T1-T12) connected to the ribs.
• Lumbar: The lower back, made up of 5 vertebrae (L1-L5).
• Sacral: Contains 5 fused vertebrae (S1-S5), forming the sacrum.
• Coccygeal: Known as the tailbone, typically with 4 fused vertebrae.

• The cervical and lumbar regions curve inward (lordosis).
• The thoracic and sacral regions curve outward (kyphosis).

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Bones of Spine

The spine, also known as the vertebral column or backbone, is made up of 33 individual bones called vertebrae., which are divided into five regions:

• Cervical (neck) region: This region includes 7 vertebrae (C1 to C7). The C1 vertebra, known as the Atlas, supports the skull and allows the nodding motion. The C2 vertebra, known as the Axis, has a peg-like structure called the odontoid process (dens) that allows rotational movement.
• Thoracic (mid-back) region: This region includes 12 vertebrae (T1 to T12). Each thoracic vertebra articulates with a pair of ribs.
• Lumbar (lower back) region: This region includes 5 vertebrae (L1 to L5). These are the largest vertebrae, supporting much of the body’s weight.
• Sacral (pelvic) region: This region includes 5 fused vertebrae (S1 to S5) forming the sacrum. The sacrum is a triangular bone that forms the back part of the pelvis.
• Coccygeal (tailbone) region: This region includes 4 fused vertebrae (Co1 to Co4) forming the coccyx. The coccyx is a small, triangular bone at the base of the vertebral column.

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Structure of Spine or Vertebral Column

The spine, or vertebral column, is a complex structure composed of bones, intervertebral discs, ligaments, and muscles. It serves multiple functions, including providing support for the body, protecting the spinal cord, and allowing flexibility and movement. Here is a detailed overview of its structure:

1. Vertebrae

The spine, or vertebral column, is composed of 33 vertebrae divided into five regions:

1. Cervical Spine: 7 vertebrae (C1-C7), with the atlas (C1) and axis (C2) allowing head movement.
2. Thoracic Spine: 12 vertebrae (T1-T12), each connected to a pair of ribs.
3. Lumbar Spine: 5 vertebrae (L1-L5), which are the largest and strongest, supporting most of the body’s weight.
4. Sacrum: 5 fused vertebrae (S1-S5) forming a triangular bone connecting the spine to the pelvis.
5. Coccyx: 4 fused vertebrae (Co1-Co4), known as the tailbone.

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2. Intervertebral Discs

Between adjacent vertebrae, there are intervertebral discs which act as cushions and provide flexibility. Each disc has two main components:

• Nucleus Pulposus: The inner gel-like core that provides the disc's elasticity and compressibility.
• Annulus Fibrosus: The outer fibrous ring that provides strength and limits excessive movement.

3. Curves of the Spine

The spine has four natural curves that help absorb shock and distribute mechanical stress during movement and activity:

• Cervical Lordosis: An inward curve at the neck.
• Thoracic Kyphosis: An outward curve at the upper back.
• Lumbar Lordosis: An inward curve at the lower back.
• Sacral Kyphosis: An outward curve at the pelvis.

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4. Spinal Cord and Nerve Roots

The vertebral column houses and protects the spinal cord, a vital part of the central nervous system that transmits signals between the brain and the rest of the body. Nerve roots branch out from the spinal cord through spaces between the vertebrae called intervertebral foramina.

5. Ligaments and Muscles

Numerous ligaments and muscles support and stabilize the spine:

• Anterior Longitudinal Ligament: Runs along the front of the vertebral bodies, preventing hyperextension.
• Posterior Longitudinal Ligament: Runs along the back of the vertebral bodies inside the spinal canal, preventing hyperflexion.
• Ligamentum Flavum: Connects the laminae of adjacent vertebrae, maintaining posture and assisting in returning to an upright position after flexion.
• Interspinous and Supraspinous Ligaments: Connect the spinous processes of adjacent vertebrae, limiting flexion.
• Intertransverse Ligaments: Connect the transverse processes, limiting lateral flexion.

Various muscles, such as the erector spinae and multifidus, are crucial for movement, support, and stabilization of the spine.

6. Joints

The spine contains several types of joints:

• Facet Joints: Synovial joints between the articular processes of adjacent vertebrae, allowing for flexibility and movement.
• Intervertebral Joints: Formed by the intervertebral discs and the adjacent vertebral bodies, providing cushioning and flexibility.

7. Blood Supply

The spine receives blood supply from various arteries, including the vertebral arteries, which supply the cervical region, and segmental arteries that provide blood to the thoracic and lumbar regions. Venous drainage is primarily through the vertebral venous plexus.

8. Development and Growth

The vertebral column develops from the notochord and somites during embryogenesis. The vertebrae start as cartilage and ossify over time, with the process continuing into early adulthood.

How many Bones in the Spine are There?

The number of bones in the spine can vary slightly between adults and children. In children, the spine consists of 33 individual bones known as vertebrae. These vertebrae are separated by intervertebral discs that serve as cushions. As children grow, the 5 sacral vertebrae in the lower spine and the 4 coccygeal vertebrae at the bottom fuse into two bones, the sacrum and the coccyx. As a result, by adulthood, the spine typically consists of 26 bones.

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