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Anterior spinal veins

Medically Reviewed by Anatomy Team

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The anterior spinal veins are a network of veins located along the anterior (ventral) surface of the spinal cord.[8] They run longitudinally from the cervical region down to the sacral region within the subarachnoid space of the spinal canal. These veins are part of the venous plexus surrounding the spinal cord and accompany the anterior spinal artery. The anterior spinal veins are responsible for draining the ventral (front) side of the spinal cord, including its gray and white matter. They communicate with the posterior spinal veins and drain into the internal vertebral venous plexus, which is situated within the vertebral column.

Location

The anterior spinal veins are located along the anterior (ventral) surface of the spinal cord, running parallel to the anterior spinal artery. These veins extend from the cervical region at the top of the spinal cord down to the sacral region at the bottom of the spinal column. They are situated within the subarachnoid space, which is filled with cerebrospinal fluid (CSF), and are closely associated with the pia mater, the innermost layer of the spinal meninges.[7] The anterior spinal veins are part of the spinal cord’s venous plexus, which helps drain blood from the spinal cord.

Anatomy

Structure

The anterior spinal veins are not single, continuous vessels but rather form a longitudinal network of veins that run along the ventral surface of the spinal cord. This network typically consists of two main anterior spinal veins, one on either side of the midline, which are interconnected by smaller transverse and oblique veins. These veins create a complex venous system that is interconnected with the posterior spinal veins and the rest of the spinal venous plexus. The anterior spinal veins are thin-walled and closely follow the course of the anterior spinal artery.

Relations

  • Anterior relations: The anterior spinal veins are situated directly on the ventral surface of the spinal cord, lying beneath the arachnoid mater and surrounded by cerebrospinal fluid (CSF) in the subarachnoid space. They run parallel to the anterior spinal artery, which supplies the spinal cord with blood.
  • Posterior relations: Behind the anterior spinal veins is the spinal cord itself, with the veins draining the blood from the ventral regions of the cord. Posterior to the spinal cord are the posterior spinal veins, which drain the dorsal aspect of the spinal cord.
  • Lateral relations: The anterior spinal veins are located near the spinal nerve roots as they emerge from the ventral aspect of the spinal cord. They also receive drainage from veins running along the sides of the spinal cord.

Venous Network and Anastomoses

The anterior spinal veins are connected to the posterior spinal veins and other veins in the spinal venous plexus through a series of transverse and oblique anastomotic veins. These small veins connect the anterior and posterior spinal veins, forming a continuous venous network that encircles the spinal cord. This network allows for efficient venous drainage from all parts of the spinal cord and ensures that blood can be redirected between the anterior and posterior systems, depending on pressure gradients or changes in posture.[6] The anastomoses between the anterior and posterior spinal veins provide multiple pathways for venous blood to exit the spinal cord.

Tributaries

The anterior spinal veins receive blood from several important tributaries that drain the spinal cord and its associated structures:

  • Medullary veins: These veins drain the central gray matter of the spinal cord, which contains the nerve cell bodies involved in motor and sensory functions. The medullary veins empty into both the anterior and posterior spinal veins.
  • Anterior sulcal veins: These small veins are located in the anterior median fissure of the spinal cord and drain the deep structures of the spinal cord. They run in the grooves along the ventral surface of the spinal cord and empty into the anterior spinal veins.
  • Radicular veins: These veins accompany the spinal nerve roots and drain the blood from the spinal cord at each vertebral level. The radicular veins connect with both the anterior and posterior spinal veins.

Course

The anterior spinal veins run longitudinally along the entire length of the spinal cord, from the cervical region to the sacral region. They are positioned along the ventral surface of the spinal cord, where they parallel the course of the anterior spinal artery.[5] As they descend through the spinal canal, they collect blood from the spinal cord and associated tissues and transport it toward the internal vertebral venous plexus, which is located in the epidural space. The anterior spinal veins maintain a close relationship with the spinal cord and the meninges throughout their course.

Termination

The anterior spinal veins drain into the internal vertebral venous plexus, which is located within the epidural space of the spinal canal. The internal vertebral venous plexus is a complex network of veins that runs along the entire length of the vertebral column, providing a pathway for venous blood to leave the spinal cord and return to the systemic circulation. From the internal vertebral venous plexus, blood is drained into larger systemic veins, such as the vertebral veins, azygos vein, and segmental veins, depending on the spinal level.

Communication with the Posterior Spinal Veins

The anterior spinal veins communicate with the posterior spinal veins through a series of transverse anastomoses. These connections form a venous ring around the spinal cord, allowing for blood flow between the anterior and posterior venous systems. This communication is important for ensuring balanced drainage from both the anterior and posterior aspects of the spinal cord and helps prevent venous congestion in any one area. The anastomotic veins provide multiple routes for blood to exit the spinal cord, depending on pressure gradients and other factors.

Variations

The anatomy of the anterior spinal veins can show anatomical variations in terms of the number of veins and their patterns of anastomosis. In some individuals, the anterior spinal veins may form a more extensive network of smaller veins, while in others, there may be larger, more prominent longitudinal veins.[4] The number and size of the transverse anastomotic veins that connect the anterior and posterior systems can also vary between individuals. These variations in the venous architecture of the spinal cord are often associated with differences in venous drainage patterns.

Surrounding Structures

  • Anteriorly: The anterior spinal veins lie on the ventral surface of the spinal cord, directly beneath the pia mater and within the subarachnoid space. Anterior to the veins is the cerebrospinal fluid (CSF) in the subarachnoid space, followed by the arachnoid mater and dura mater.
  • Posteriorly: The veins are positioned on the anterior surface of the spinal cord, which separates them from the posterior spinal veins and the structures of the dorsal spinal cord.
  • Lateral relations: The anterior spinal veins run near the ventral nerve roots and are connected to lateral venous branches that accompany the radicular arteries and veins.

Function

Venous Drainage of the Anterior Spinal Cord

The primary function of the anterior spinal veins is to drain venous blood from the anterior (ventral) surface of the spinal cord. These veins collect deoxygenated blood from the tissues of the spinal cord, including the anterior gray and white matter, and transport it away from the spinal cord. The anterior spinal veins ensure that blood is continuously drained from the spinal cord’s anterior regions, preventing venous stasis and ensuring proper circulation within the spinal cord.

Drainage from the Ventral Gray and White Matter

The anterior spinal veins drain blood from the ventral gray matter, which contains motor neurons responsible for sending signals from the spinal cord to muscles, and from the ventral white matter, which contains motor and sensory pathways. The veins remove deoxygenated blood and metabolic waste from these areas, allowing the nervous tissue to function properly. Efficient venous drainage from the gray and white matter ensures that nutrients and oxygen can be replenished while metabolic byproducts are transported away.

Removal of Metabolic Waste from the Spinal Cord

One of the critical functions of the anterior spinal veins is the removal of metabolic waste products from the spinal cord. During normal physiological processes, neurons and glial cells in the spinal cord produce metabolic byproducts such as carbon dioxide, lactate, and other waste materials. The anterior spinal veins play a crucial role in clearing these byproducts, which helps maintain the metabolic balance and ensures optimal functioning of the spinal cord.[3] By efficiently removing waste, these veins help prevent the accumulation of harmful substances in the spinal cord tissue.

Venous Return from the Anterior Sulcal Region

The anterior spinal veins are also responsible for draining the anterior sulcal veins, which run in the anterior median fissure of the spinal cord. This fissure is a deep groove along the ventral surface of the spinal cord, and it houses important blood vessels that supply and drain the spinal cord. The anterior sulcal veins help drain the deeper structures of the spinal cord, and the anterior spinal veins collect and transport this blood toward the larger venous systems. This drainage is essential for maintaining circulation in the central portions of the spinal cord, particularly in regions involved in motor control.

Connection with the Posterior Spinal Veins

The anterior spinal veins are connected to the posterior spinal veins via transverse anastomotic veins that allow for balanced venous drainage between the ventral and dorsal aspects of the spinal cord. This interconnected venous system helps regulate pressure within the spinal cord’s venous network, allowing blood to flow efficiently between the anterior and posterior systems depending on the pressure gradients. This communication ensures that blood can be diverted from areas of higher pressure to areas of lower pressure, helping prevent venous congestion and promoting balanced circulation throughout the spinal cord.

Venous Return from Spinal Nerve Roots

The anterior spinal veins also drain blood from the ventral nerve roots, which emerge from the spinal cord and transmit motor signals to the muscles. These veins ensure that the nerve roots are properly drained of venous blood, allowing for the removal of waste and the maintenance of proper venous pressure in the region. The ventral nerve roots are crucial for motor function, and efficient venous drainage ensures that these structures remain healthy and functional.

Drainage into the Internal Vertebral Venous Plexus

The anterior spinal veins drain into the internal vertebral venous plexus, a large venous network located in the epidural space surrounding the spinal cord.[2] This plexus serves as a major pathway for venous blood from the spinal cord to return to the central circulation. By draining into this venous plexus, the anterior spinal veins help transport deoxygenated blood away from the spinal cord and toward the larger systemic venous circulation. This connection to the vertebral venous plexus is essential for ensuring efficient venous return from the entire length of the spinal cord.

Support for Venous Return During Spinal Movement

The anterior spinal veins assist in maintaining venous return during spinal movements, such as bending, twisting, or stretching. As the spine moves, pressure within the spinal canal can fluctuate, and the anterior spinal veins must adapt to these changes in pressure. The network of anastomoses connecting the anterior spinal veins to the posterior spinal veins and the internal vertebral venous plexus helps buffer these pressure fluctuations. This adaptability ensures that blood continues to flow smoothly through the spinal cord’s venous network even during movement, preventing venous congestion or interruption in blood flow.

Regulation of Venous Pressure in the Spinal Cord

The anterior spinal veins play a crucial role in regulating venous pressure within the spinal cord. By distributing blood flow between the anterior and posterior venous systems, they help balance the pressure in different regions of the spinal cord. This regulation is important for maintaining a stable environment within the spinal cord, ensuring that blood flow is not compromised by localized increases in venous pressure. The anastomotic connections between the anterior and posterior systems provide flexibility in venous drainage, allowing blood to be diverted as needed to maintain optimal venous return.

Venous Drainage from the Meninges

The anterior spinal veins also contribute to draining the meninges, particularly the pia mater, which is closely associated with the surface of the spinal cord. The pia mater contains a rich vascular network that supports the spinal cord, and the anterior spinal veins help remove venous blood from this layer. By draining blood from the pia mater and surrounding meninges, the anterior spinal veins play an important role in maintaining the health of the spinal cord’s protective coverings.

Contribution to the Systemic Venous Return

Ultimately, the anterior spinal veins are part of the larger venous system that helps return blood to the heart.[1] By collecting deoxygenated blood from the spinal cord and draining it into the internal vertebral venous plexus, the anterior spinal veins contribute to the systemic venous return. This blood is eventually transported through larger veins, such as the vertebral veins and the azygos system, back to the superior vena cava and the right atrium of the heart. The efficient functioning of the anterior spinal veins ensures that blood from the spinal cord is continuously returned to the systemic circulation for reoxygenation.

Clinical Significance

The anterior spinal veins are clinically significant due to their involvement in spinal cord circulation and their proximity to critical structures such as the anterior spinal artery. Obstruction or compression of these veins can lead to impaired venous drainage from the spinal cord, resulting in conditions such as spinal cord edema or venous congestion, which can lead to neurological deficits such as weakness, numbness, or paralysis.

In conditions like spinal cord tumors, epidural hematomas, or arteriovenous malformations, the anterior spinal veins can become compromised, contributing to increased pressure within the spinal cord. During surgical procedures involving the spine, such as spinal decompression or tumor resection, careful handling of these veins is necessary to avoid complications like bleeding or spinal cord injury.

References

  1. Williams, P. L., Bannister, L. H., Berry, M. M., Collins, P., Dyson, M., & Dussek, J. E. (1995). Gray’s Anatomy: The Anatomical Basis of Medicine and Surgery (38th ed.). Churchill Livingstone.
  2. Bergman, R. A., Afifi, A. K., & Miyauchi, R. (2011). Anatomy of the Human Body (2nd ed.). Urban & Schwarzenberg.
  3. Snell, R. S. (2012). Clinical Anatomy by Regions (9th ed.). Lippincott Williams & Wilkins.
  4. Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2018). Clinically Oriented Anatomy (8th ed.). Lippincott Williams & Wilkins.
  5. Rohen, J. W., & Yokochi, C. (2015). Color Atlas of Anatomy: A Photographic Study of the Human Body (7th ed.). Wolters Kluwer.
  6. Latarjet, M. (2001). Anatomy of the Human Body (6th ed.). Wiley-Blackwell.
  7. McMinn, R. M. H., & Abrahams, P. H. (2014). McMinn’s Color Atlas of Human Anatomy (6th ed.). Elsevier.
  8. Tandler, J., & Hennemann, H. (2007). Anatomy of the Human Vertebral Column and Spinal Cord. Springer.