The intervertebral veins are located along the vertebral column, passing through the intervertebral foramina—the openings between adjacent vertebrae. These veins drain blood from the internal vertebral venous plexus, which is situated in the epidural space of the vertebral canal, and the external vertebral venous plexus, which lies outside the vertebrae. The intervertebral veins emerge through the intervertebral foramina at each vertebral level, allowing venous blood to exit the vertebral column. Once outside the foramina, these veins connect with segmental veins, such as the vertebral veins, lumbar veins, and intercostal veins, which transport blood back toward the heart.
Structure and Anatomy
Location
The intervertebral veins are located along the entire length of the vertebral column, passing through the intervertebral foramina at each vertebral level. These foramina are openings between adjacent vertebrae through which spinal nerves, arteries, and veins pass. The intervertebral veins are situated between the vertebrae, connecting the venous systems inside the vertebral canal to the external venous networks. They provide a crucial pathway for venous drainage from both the internal vertebral venous plexus (within the spinal canal) and the external vertebral venous plexus (outside the vertebrae).
Structure
The intervertebral veins are relatively large veins that exit the vertebral canal through the intervertebral foramina. These veins serve as conduits for venous blood from the internal vertebral venous plexus, which runs longitudinally inside the vertebral canal. After passing through the intervertebral foramina, the intervertebral veins continue to external venous networks, connecting with segmental veins at each vertebral level. The veins are paired with other structures passing through the intervertebral foramina, such as the spinal nerves and radicular arteries. Their structure allows them to accommodate the large volume of blood that must be drained from the vertebral column.
Relations
- Anterior relations: The intervertebral veins are closely related to the vertebral bodies and the intervertebral discs, which form the anterior part of the vertebral column. They pass through the foramina near these structures, helping to drain the vertebrae.
- Posterior relations: Posterior to the intervertebral veins are the laminae and articular processes of the vertebrae, which form the posterior portion of the vertebral canal. The veins run close to these structures as they pass through the intervertebral foramina.
- Lateral relations: The spinal nerves are closely associated with the intervertebral veins, as they pass through the same intervertebral foramina. The veins lie next to the spinal nerves, with small radicular veins sometimes draining directly into the intervertebral veins.
- Superior and inferior relations: The intervertebral veins are located between adjacent vertebrae, passing through the intervertebral foramina. Superiorly and inferiorly, they are bounded by the pedicles of the vertebrae, which form part of the walls of the foramina.
Communication with the Internal Vertebral Venous Plexus
The intervertebral veins are major conduits for blood exiting the internal vertebral venous plexus. The internal vertebral venous plexus is a network of interconnected veins that runs longitudinally within the epidural space of the vertebral canal. This plexus is located anterior and posterior to the spinal cord, providing venous drainage from the vertebrae and the spinal cord. The intervertebral veins receive blood from this plexus and transport it out of the vertebral canal through the intervertebral foramina, ensuring that blood is drained efficiently from the vertebral column.
Communication with the External Vertebral Venous Plexus
In addition to draining the internal vertebral venous plexus, the intervertebral veins also communicate with the external vertebral venous plexus, which surrounds the outer surface of the vertebrae. This external plexus provides venous drainage for the outer parts of the vertebrae, including the muscles, ligaments, and other soft tissues of the back. The intervertebral veins connect the internal and external vertebral venous plexuses, forming a continuous venous network that drains both the internal and external structures of the vertebral column.
Tributaries
The intervertebral veins receive several important tributaries that contribute to the venous drainage of the vertebral column:
- Radicular veins: These veins accompany the spinal nerve roots and drain the blood from the nerve roots and surrounding tissues. They join the intervertebral veins as they pass through the intervertebral foramina, contributing venous blood from the spinal nerves.
- Basivertebral veins: These veins drain the cancellous bone of the vertebral bodies and communicate with the intervertebral veins through the internal vertebral venous plexus.
- Venous branches from the dura mater: Small veins draining the dura mater, the outermost layer of the meninges that cover the spinal cord, contribute to the venous blood flowing into the intervertebral veins.
Course
The intervertebral veins run through the intervertebral foramina at each vertebral level, forming part of the venous drainage system of the spine. They begin within the vertebral canal, where they collect blood from the internal vertebral venous plexus. The veins pass through the intervertebral foramina, located between the pedicles of adjacent vertebrae, and exit the vertebral canal. Once outside the vertebral canal, they connect with the external vertebral venous plexus and join other systemic veins, such as the vertebral veins, intercostal veins, lumbar veins, or sacral veins, depending on their location along the vertebral column.
Termination
After passing through the intervertebral foramina, the intervertebral veins terminate by draining into segmental veins at each vertebral level. These segmental veins vary depending on the region of the vertebral column:
- In the cervical region, the intervertebral veins terminate in the vertebral veins, which run along the sides of the cervical vertebrae.
- In the thoracic region, they terminate in the intercostal veins, which are located between the ribs and drain the thoracic wall.
- In the lumbar region, they terminate in the lumbar veins, which drain the lower back and abdominal regions.
- In the sacral region, they terminate in the sacral veins, which are part of the venous network of the pelvis.
Surrounding Structures
- Anteriorly: The vertebral bodies and intervertebral discs form the anterior boundary of the intervertebral foramina through which the intervertebral veins pass.
- Posteriorly: The vertebral laminae and the articular processes of adjacent vertebrae form the posterior part of the intervertebral foramina.
- Lateral relations: The spinal nerves are closely associated with the intervertebral veins as they both pass through the intervertebral foramina.
Variations
The anatomy of the intervertebral veins can show anatomical variations in size, course, and termination. In some individuals, the veins may be larger or more prominent, depending on the volume of blood they must drain. The connections between the intervertebral veins and the external vertebral venous plexus may also vary, with different patterns of venous anastomosis seen between individuals. Additionally, the number of tributaries contributing to the intervertebral veins can vary slightly at different vertebral levels.
Function
Venous Drainage of the Vertebral Column
The primary function of the intervertebral veins is to drain venous blood from the vertebral column, including the vertebrae, spinal cord, and surrounding tissues. These veins collect deoxygenated blood from the vertebral bodies, spinal nerve roots, and other structures within the vertebral canal. After collecting the blood, the intervertebral veins pass through the intervertebral foramina, ensuring the blood exits the vertebral column efficiently and connects with the larger systemic venous circulation.
Drainage from the Internal Vertebral Venous Plexus
One of the main roles of the intervertebral veins is to drain blood from the internal vertebral venous plexus, which is located within the epidural space of the spinal canal. The internal vertebral venous plexus is a network of veins that collects blood from the spinal cord, vertebral bodies, and meninges. The intervertebral veins act as conduits, allowing blood from this plexus to leave the vertebral canal and drain into systemic veins, such as the vertebral veins in the cervical region or the intercostal and lumbar veins in the thoracic and lumbar regions. This drainage is essential for maintaining normal blood circulation within the spinal column.
Drainage from the External Vertebral Venous Plexus
The intervertebral veins also drain venous blood from the external vertebral venous plexus, which is located on the outer surface of the vertebrae. The external plexus drains the muscles, ligaments, and soft tissues surrounding the vertebral column. The intervertebral veins provide a connection between this external venous network and the internal venous system, facilitating venous return from the structures outside the vertebrae. This communication ensures that blood from both the internal and external parts of the vertebral column is effectively drained.
Removal of Metabolic Waste from the Vertebrae
The intervertebral veins play an important role in removing metabolic waste products from the vertebrae and surrounding tissues. During cellular metabolism, the vertebral bodies and soft tissues of the spine produce metabolic byproducts, including carbon dioxide and other waste materials. The intervertebral veins collect deoxygenated blood containing these waste products and transport it out of the vertebral column, ensuring that the vertebrae remain healthy and properly metabolized. By removing waste products, the veins help maintain the health and function of the vertebral structures.
Venous Drainage from the Spinal Nerves
The intervertebral veins also assist in draining venous blood from the spinal nerve roots, which pass through the same intervertebral foramina. The spinal nerves, particularly the ventral and dorsal roots, require efficient venous drainage to prevent congestion and maintain proper function. The intervertebral veins collect blood from the radicular veins that accompany the spinal nerve roots and transport this blood out of the vertebral canal. This function ensures that the nerve roots are not compromised by venous stasis, which could lead to nerve compression or dysfunction.
Connection to Segmental Veins and Systemic Circulation
The intervertebral veins serve as a crucial link between the vertebral column and the segmental veins at each vertebral level, such as the vertebral veins, intercostal veins, lumbar veins, and sacral veins. These segmental veins are part of the systemic venous system, which returns deoxygenated blood to the heart. The intervertebral veins connect the vertebral venous system with the segmental veins, allowing venous blood from the spine to be transported to the larger veins that eventually drain into the superior vena cava and inferior vena cava. This connection ensures that venous return from the vertebral column is seamlessly integrated into the body’s overall circulation.
Support for Venous Return During Movement
The intervertebral veins play a key role in supporting venous return during spinal movement, including flexion, extension, and rotation of the spine. As the vertebral column moves, pressure changes within the vertebral canal and the surrounding structures can affect venous flow. The intervertebral veins, along with the internal and external vertebral venous plexuses, are highly adaptable and can accommodate these pressure changes, ensuring that venous blood continues to flow smoothly despite the movement of the spine. This ability to maintain venous return during dynamic spinal motion is essential for preventing venous congestion and ensuring continuous drainage.
Prevention of Venous Congestion
By providing an efficient pathway for venous blood to exit the vertebral column, the intervertebral veins help prevent venous congestion within the spine. Venous congestion can occur if blood flow is obstructed or slowed, leading to a buildup of pressure and blood within the vertebrae, spinal cord, or surrounding tissues. This congestion can impair spinal function and lead to pain, swelling, or even neurological symptoms. The intervertebral veins ensure that blood is constantly drained from the vertebral column, preventing the buildup of pressure and maintaining proper circulation.
Drainage from the Meninges
The meninges, the protective layers surrounding the spinal cord, also rely on the intervertebral veins for venous drainage. Small veins from the dura mater, the outermost meningeal layer, drain into the internal vertebral venous plexus, which in turn drains into the intervertebral veins. This drainage is important for maintaining the health of the meninges and ensuring that blood flow within the spinal canal remains balanced. By draining the meninges, the intervertebral veins help support the overall circulation within the spinal cord and protect the delicate structures of the central nervous system.
Regulation of Venous Pressure in the Spine
The intervertebral veins contribute to the regulation of venous pressure within the vertebral column. By connecting the internal and external venous plexuses and allowing blood to flow into the larger segmental veins, the intervertebral veins help balance pressure within the venous system of the spine. This regulation is important for maintaining a stable environment within the vertebral canal and ensuring that blood flow remains unobstructed. If pressure increases within the internal vertebral venous plexus, the intervertebral veins allow blood to flow into lower-pressure areas, preventing the development of conditions like venous congestion or spinal cord compression.
Clinical Significance
The intervertebral veins are clinically significant due to their role in venous drainage from the vertebral column and their proximity to critical structures such as the spinal nerves and spinal cord. Any disruption to these veins, such as during spinal surgery or in conditions like vertebral fractures or spinal tumors, can lead to complications such as venous congestion, bleeding, or compression of spinal nerves. Their connections to both the internal and external vertebral venous plexuses make them important pathways for venous blood drainage, and they can be involved in the spread of infections or metastatic cancer to the spine.
In conditions like vertebral hemangiomas or spinal arteriovenous malformations (AVMs), these veins may become engorged, leading to pain and other complications. Additionally, because the vertebral venous system is valveless, increased intra-abdominal or intrathoracic pressure can cause blood to backflow, affecting spinal venous circulation and contributing to conditions such as spinal venous thrombosis. Understanding the anatomy of the intervertebral veins is crucial in spinal surgeries and diagnostic procedures to avoid complications related to venous injury.
