Lateral sacral artery

The lateral sacral artery is a branch of the posterior division of the internal iliac artery and is responsible for supplying blood to the sacrum and surrounding structures. There are typically two lateral sacral arteries, a superior and an inferior branch, although this can vary between individuals. These arteries provide vascular support to the sacral vertebrae, spinal meninges, and nearby muscles and tissues.

Location

The lateral sacral artery is located in the pelvic region. It originates from the posterior division of the internal iliac artery and travels medially along the sacrum. The superior and inferior branches run parallel to the sacral foramina, small openings in the sacral bone, and send branches through these foramina to supply the sacral canal and nerves. The artery also gives branches that contribute to the blood supply of surrounding muscles and connective tissues in the posterior pelvic region.

Structure and Anatomy

The lateral sacral artery is an essential artery within the pelvic region, contributing to the blood supply of the sacrum, spinal meninges, and surrounding muscles. It is a branch of the posterior division of the internal iliac artery and usually divides into superior and inferior branches. Below is a detailed description of its anatomy.

Origin

The lateral sacral artery originates from the posterior division of the internal iliac artery, which supplies blood to the pelvic walls and adjacent structures. It is one of the three primary branches of this division, along with the iliolumbar and superior gluteal arteries. Typically, the lateral sacral artery gives rise to two branches—superior and inferior—but anatomical variations can occur.

Course

After arising from the posterior division of the internal iliac artery, the lateral sacral artery courses medially towards the sacrum, running along the posterior pelvic wall. It travels along the anterior surface of the sacrum, following the contour of the sacral bone, with its branches lying close to the sacral foramina (the small openings in the sacral vertebrae).

Branches

The lateral sacral artery typically divides into superior and inferior branches, which are responsible for supplying blood to various structures in the sacral and pelvic region.

Superior Branch:

• The superior branch of the lateral sacral artery ascends along the upper portion of the sacrum and provides blood to the upper sacral vertebrae and surrounding tissues. It also sends small branches through the sacral foramina, which are openings in the sacral vertebrae, to supply the spinal meninges and sacral nerves within the sacral canal.
• The superior branch anastomoses (connects) with other arteries, such as the iliolumbar artery, contributing to a network of vessels that supplies the pelvic and lumbar regions.

Inferior Branch:

• The inferior branch descends along the lower part of the sacrum, supplying the lower sacral vertebrae, coccyx, and nearby pelvic muscles. Like the superior branch, the inferior branch sends vessels through the sacral foramina to supply the sacral canal and spinal nerves.
• The inferior branch may also anastomose with the middle sacral artery and other pelvic arteries, ensuring a comprehensive vascular supply to the sacrum and surrounding areas.

Relations to Other Structures

The lateral sacral artery runs along several important structures in the pelvic region:

• Sacral Vertebrae: The lateral sacral artery lies close to the sacral vertebrae, supplying the bones and passing through the sacral foramina to reach deeper structures. These foramina allow the lateral sacral artery to supply the sacral nerves and meninges within the sacral canal.
• Sacral Nerves: As the lateral sacral artery sends branches through the sacral foramina, it supplies the sacral nerves, which exit through these openings and contribute to the innervation of the lower limbs and pelvic organs.
• Iliolumbar Artery: The lateral sacral artery is in proximity to the iliolumbar artery, with which it forms anastomoses. This relationship ensures that both arteries contribute to the blood supply of the sacrum, lumbar vertebrae, and surrounding tissues.

Anastomoses

The lateral sacral artery forms several important anastomoses with other arteries in the pelvic region, which helps create a robust vascular network:

• Iliolumbar Artery: The superior branch of the lateral sacral artery anastomoses with the iliolumbar artery, which also supplies the lumbar vertebrae and muscles of the lower back.
• Superior Gluteal Artery: The lateral sacral artery anastomoses with the superior gluteal artery, which provides blood to the gluteal region and surrounding muscles.
• Middle Sacral Artery: The inferior branch of the lateral sacral artery may form anastomoses with the middle sacral artery, further contributing to the blood supply of the sacral vertebrae and coccyx.

Variations

While the lateral sacral artery typically divides into superior and inferior branches, anatomical variations are possible. Some individuals may have a single lateral sacral artery or additional smaller branches that extend to other structures in the pelvis. The exact branching pattern may vary, but the artery generally follows a consistent course along the sacrum.

Function

The lateral sacral artery performs several essential functions related to the vascular supply of the sacrum, spinal nerves, and surrounding pelvic structures. Below is a detailed explanation of its specific roles.

Blood Supply to the Sacrum

The primary function of the lateral sacral artery is to supply oxygenated blood to the sacral vertebrae. The sacrum is a large, triangular bone located at the base of the spine, forming the posterior part of the pelvic girdle. The lateral sacral artery ensures that the bone tissue of the sacrum is nourished and supported with a continuous blood supply, which is vital for maintaining the structural integrity of this region.

• Superior Sacral Vertebrae: The superior branch of the lateral sacral artery supplies the upper part of the sacrum, including the first few sacral vertebrae.
• Inferior Sacral Vertebrae: The inferior branch of the artery descends along the lower portion of the sacrum, providing blood to the lower sacral vertebrae and the coccyx.

Blood Supply to the Sacral Canal and Meninges

The lateral sacral artery sends small branches through the sacral foramina, which are openings in the sacral bone, to supply the sacral canal. Inside the sacral canal, these branches provide blood to the spinal meninges, the protective membranes surrounding the spinal cord.

• Meningeal Support: The spinal meninges, including the dura mater, arachnoid mater, and pia mater, are essential for protecting the sacral nerves and spinal cord, and the lateral sacral artery supplies blood to these layers in the sacral region.
• Vascularization of the Sacral Nerves: Through the sacral foramina, the lateral sacral artery also supplies the sacral nerves, which exit from the spinal cord and innervate the lower limbs and pelvic organs. This ensures that these critical nerves have the blood supply needed to function properly.

Blood Supply to the Muscles and Soft Tissues of the Pelvis

The lateral sacral artery also supplies blood to several muscles and soft tissues in the posterior pelvic region. By providing a vascular supply to the pelvic muscles, the artery supports the movement and stability of the pelvis.

• Muscles of the Pelvic Wall: The lateral sacral artery contributes to the vascularization of the muscles located along the pelvic wall, including the piriformis and coccygeus muscles, which assist in pelvic stability and movement.
• Gluteal Region: The lateral sacral artery anastomoses with the superior gluteal artery, indirectly contributing to the blood supply of the gluteal muscles, which are important for posture, walking, and movement of the lower limbs.

Contribution to the Pelvic Vascular Network

The lateral sacral artery forms important anastomoses with other arteries in the pelvic and lumbar regions, creating a robust network that ensures consistent blood flow to the pelvic organs, vertebrae, and surrounding tissues. These anastomotic connections provide a safety net in cases where blood flow may be restricted in other arteries due to injury or disease.

• Anastomosis with the Iliolumbar Artery: The superior branch of the lateral sacral artery forms connections with the iliolumbar artery, which supplies the lumbar vertebrae and muscles of the lower back. This anastomosis helps ensure continuous blood supply to the lower spine.
• Anastomosis with the Superior Gluteal Artery: The lateral sacral artery also anastomoses with the superior gluteal artery, contributing to the blood supply of the gluteal muscles and surrounding tissues.
• Anastomosis with the Middle Sacral Artery: The inferior branch of the lateral sacral artery may anastomose with the middle sacral artery, which supplies the lower sacrum and coccyx. This connection helps provide additional blood flow to the sacral region, especially in the case of injury or blockage in the middle sacral artery.

Support for Bone Health and Repair

The blood supply provided by the lateral sacral artery is critical for the health of the sacral bones. By delivering oxygen and nutrients to the sacrum, the artery helps support bone maintenance, growth, and repair, especially in cases of injury or surgery involving the sacrum. Fractures or surgical interventions in the sacral region rely on a steady blood supply to promote healing.

• Bone Nourishment: The lateral sacral artery ensures that the sacrum receives adequate nourishment to maintain its strength and functionality.
• Healing After Trauma: After fractures or surgical procedures involving the sacrum or surrounding structures, the artery’s blood supply plays a vital role in the healing and regeneration of bone tissue.

Support for Nerve Function

The lateral sacral artery’s role in supplying blood to the sacral nerves is essential for maintaining proper nerve function. The sacral nerves, which exit through the sacral foramina, are responsible for transmitting signals between the spinal cord and the lower limbs, pelvic floor, and pelvic organs. By providing blood to these nerves, the artery ensures that they receive the oxygen and nutrients needed for proper nerve conduction.

Sacral Nerve Support: These nerves are involved in motor and sensory functions of the lower limbs and pelvic organs, and the blood supply from the lateral sacral artery is critical for their proper operation.

Contribution to Spinal and Pelvic Stability

The lateral sacral artery, through its blood supply to the sacral vertebrae, muscles, and ligaments, indirectly supports the stability and function of the pelvic girdle and lower spine. The sacrum forms the posterior part of the pelvic girdle, and the blood flow from the lateral sacral artery ensures that this region remains healthy, stable, and capable of supporting the weight of the upper body.

Pelvic Girdle Stability: By supplying the bones, muscles, and ligaments of the sacral region, the artery plays a role in maintaining the structural integrity of the pelvis, which is essential for weight-bearing and movement.

Clinical Significance

The lateral sacral artery is clinically significant due to its role in supplying blood to the sacrum, sacral nerves, spinal meninges, and surrounding pelvic muscles. Its branches that pass through the sacral foramina provide essential blood flow to the sacral canal and spinal nerves, making it important in spinal and pelvic surgeries. Injury to this artery during surgical procedures, such as spinal decompression or pelvic tumor removal, can lead to significant bleeding and complications due to its vascular supply to key nerves and tissues.

In cases of trauma, such as sacral fractures, maintaining the integrity of the lateral sacral artery is vital for proper healing and bone repair. Its role in supplying the sacral vertebrae and supporting bone health also makes it important in orthopedic interventions. Additionally, its anastomoses with other arteries, like the iliolumbar and superior gluteal arteries, contribute to a robust vascular network in the pelvis, ensuring adequate blood flow even if other vessels are compromised.