Sigmoid arteries

Medically Reviewed by Anatomy Team

Last updated on December 27, 2024

The sigmoid arteries are branches of the inferior mesenteric artery that supply blood to the sigmoid colon, a section of the large intestine. These arteries typically consist of two to four branches that emerge from the inferior mesenteric artery, which itself arises from the abdominal aorta. The sigmoid arteries provide the essential blood supply to the curved part of the colon known as the sigmoid colon, which connects the descending colon to the rectum.

Location

The sigmoid arteries are located in the lower left quadrant of the abdomen. They arise from the inferior mesenteric artery as it travels toward the pelvis. These arteries run through the mesocolon, the fold of tissue attaching the colon to the posterior abdominal wall, and extend toward the sigmoid colon. They form important anastomoses with the left colic artery and superior rectal artery to ensure continuous blood flow to the lower part of the colon.

Anatomy

The sigmoid arteries are essential vessels that supply blood to the sigmoid colon, a part of the large intestine responsible for forming and transporting feces. These arteries branch from the inferior mesenteric artery and have a complex network of anastomoses that ensure a continuous blood supply. Below is a detailed description of their anatomy, including their origin, course, branches, and relations to other structures.

Origin

The sigmoid arteries arise from the inferior mesenteric artery (IMA), which is one of the three major branches of the abdominal aorta that supplies blood to the large intestine. The inferior mesenteric artery typically originates from the abdominal aorta at the level of the third lumbar vertebra (L3), and the sigmoid arteries are among the final branches to emerge from the inferior mesenteric artery before it continues as the superior rectal artery.

The number of sigmoid arteries varies between individuals, with most people having between two to four branches. These arteries are typically referred to as the first, second, and third sigmoid arteries, depending on their position along the sigmoid colon.

Course

After branching off from the inferior mesenteric artery, the sigmoid arteries descend obliquely through the mesocolon, a peritoneal fold that suspends the colon from the posterior abdominal wall. The sigmoid arteries run within the mesocolon and travel toward the sigmoid colon, a S-shaped segment of the large intestine located between the descending colon and the rectum.

Direction and Path: The sigmoid arteries follow a curved or oblique path as they course inferiorly and medially toward the sigmoid colon. The arteries run along the posterior abdominal wall, passing anterior to the psoas major muscle and left ureter.

Branches and Anastomoses

The sigmoid arteries divide into multiple smaller branches as they approach the sigmoid colon, forming a network of vessels that ensure robust blood supply to the region. These branches form important anastomoses (connections) with other arteries in the region to provide a continuous blood flow.

Branches: As the sigmoid arteries approach the sigmoid colon, they give off small branches that enter the wall of the colon, penetrating the muscular layers and forming a dense capillary network in the mucosa and submucosa. This vascular network is essential for nourishing the tissues of the sigmoid colon and maintaining the function of its epithelial lining.
Anastomoses with the Left Colic Artery: The sigmoid arteries form anastomoses with the left colic artery, which is also a branch of the inferior mesenteric artery. This connection helps ensure a steady blood supply to the sigmoid and descending colon, especially in situations where one arterial pathway may be compromised.
Anastomoses with the Superior Rectal Artery: The sigmoid arteries also connect with the superior rectal artery, which is the terminal branch of the inferior mesenteric artery and supplies the rectum. These anastomoses ensure blood flow between the sigmoid colon and rectum, supporting the transition of blood supply as the large intestine approaches the pelvic region.
Marginal Artery (of Drummond): The branches of the sigmoid arteries contribute to the formation of the marginal artery, a continuous arterial network that runs along the inner border of the colon. This artery plays a critical role in maintaining blood supply to the colon, especially when the primary blood vessels are blocked or narrowed.

Relations to Other Structures

The sigmoid arteries, like other branches of the inferior mesenteric artery, are situated in close proximity to several key anatomical structures as they course through the lower abdomen and pelvis.

Psoas Major Muscle: The sigmoid arteries cross over the psoas major muscle, a large muscle responsible for hip flexion, which runs along the posterior abdominal wall. This anatomical relationship is important during surgeries involving the lower abdomen or pelvis.
Left Ureter: The sigmoid arteries cross anterior to the left ureter, which carries urine from the left kidney to the bladder. This close relationship between the arteries and the ureter is significant in surgical procedures or medical conditions affecting the lower abdomen and pelvis.
Inferior Mesenteric Vein: The inferior mesenteric vein often runs parallel to the inferior mesenteric artery and its branches, including the sigmoid arteries. This vein is responsible for draining deoxygenated blood from the colon, and its proximity to the sigmoid arteries is important in understanding the vascular dynamics of the region.

Blood Flow Distribution

The sigmoid arteries supply oxygenated blood to the sigmoid colon, which is the lower part of the large intestine where fecal matter is stored and further compacted before passing into the rectum. The vascular branches of the sigmoid arteries penetrate the muscular and mucosal layers of the sigmoid colon, ensuring adequate nourishment and oxygenation of the colon’s tissues.

Mucosa and Submucosa: The sigmoid arteries supply the mucosa and submucosa of the sigmoid colon, which are essential for nutrient absorption, water reabsorption, and mucus secretion. The blood supply to these layers helps maintain the integrity of the epithelial lining and supports the function of the colon in preparing waste material for elimination.
Muscular Layers: The smooth muscle layers of the sigmoid colon, which are responsible for peristalsis (the rhythmic contractions that move material through the digestive tract), receive blood from the sigmoid arteries. This ensures that the muscular layers are adequately oxygenated and capable of performing their function of moving fecal matter through the colon.

Variations

The anatomy of the sigmoid arteries can vary between individuals, particularly in the number and branching patterns of the arteries. Some of the key variations include:

Number of Sigmoid Arteries: Most individuals have two to four sigmoid arteries, but there can be variations in the exact number. In some individuals, only one large sigmoid artery may be present, while others may have multiple smaller arteries supplying the region.
Origin of Branches: The precise origin of the sigmoid arteries along the inferior mesenteric artery may also vary. In some individuals, the arteries may arise higher or lower along the main trunk of the inferior mesenteric artery.

Function

The sigmoid arteries perform several important functions by supplying blood to the sigmoid colon and contributing to the vascular network of the large intestine. Their role is crucial for maintaining the health and function of the lower gastrointestinal tract. Below is a detailed explanation of the functions of the sigmoid arteries.

Blood Supply to the Sigmoid Colon

The primary function of the sigmoid arteries is to provide oxygenated blood to the sigmoid colon, a part of the large intestine that connects the descending colon to the rectum. The sigmoid colon is responsible for storing fecal matter and preparing it for evacuation through the rectum.

Oxygen and Nutrient Delivery: The sigmoid arteries ensure that the tissues of the sigmoid colon receive a constant supply of oxygen and nutrients. This is essential for the colon’s epithelial lining, which absorbs water and electrolytes, and for the muscle layers that facilitate the movement of waste material through peristalsis.
Support for Smooth Muscle Function: The arteries supply the muscularis externa, the smooth muscle layer of the colon, enabling proper contractions and peristalsis. These rhythmic contractions move stool toward the rectum, ensuring proper digestion and elimination.

Contribution to Marginal Artery (of Drummond)

The sigmoid arteries contribute to the formation of the marginal artery, a critical vascular structure that runs along the border of the colon. The marginal artery connects the branches of the superior mesenteric artery and the inferior mesenteric artery, providing a collateral circulation pathway for the large intestine.

Collateral Blood Flow: Through their contributions to the marginal artery, the sigmoid arteries ensure that the sigmoid colon receives continuous blood supply, even in cases where other arteries are compromised or obstructed. This collateral flow is essential for maintaining the health of the colon, particularly in conditions like atherosclerosis, where arterial blockages may occur.
Anastomoses with Other Arteries: The sigmoid arteries form anastomoses with the left colic artery (which supplies the descending colon) and the superior rectal artery (which supplies the rectum). These connections are important for sustaining blood flow throughout the lower part of the colon.

Support for Absorption and Secretion in the Sigmoid Colon

The sigmoid arteries play a crucial role in maintaining the functionality of the mucosal layer of the sigmoid colon, which is responsible for the final stages of water and electrolyte absorption and mucus secretion to aid the passage of feces.

Absorption of Water and Electrolytes: The blood supplied by the sigmoid arteries allows the mucosal layer of the sigmoid colon to absorb water and electrolytes from the remaining digestive material. This process is essential for forming solid stool and preventing dehydration.
Mucus Secretion: The oxygen and nutrients delivered by the sigmoid arteries support the goblet cells in the mucosa, which secrete mucus. This mucus lubricates the colon’s inner surface, facilitating the smooth passage of stool toward the rectum.

Blood Supply to the Colon’s Nerves and Lymphatic Tissues

The sigmoid arteries also supply blood to the nerves and lymphatic tissues associated with the sigmoid colon, contributing to the overall function of the lower gastrointestinal tract.

Support for Nerve Function: The sigmoid arteries provide blood to the nerve fibers that innervate the sigmoid colon. These nerves are responsible for controlling the contractions of the colon’s smooth muscle, ensuring proper peristalsis and stool movement.
Lymphatic Drainage Support: The blood supply from the sigmoid arteries helps support the lymphatic system within the sigmoid colon, allowing lymphatic tissues to function properly in defending against infections and draining excess fluid from the colon’s tissues.

Role in Tissue Healing and Repair

The blood supplied by the sigmoid arteries is essential for tissue repair and healing in the sigmoid colon, particularly following injury, inflammation, or surgical intervention.

Healing After Surgery: After surgical procedures such as a sigmoidectomy (resection of the sigmoid colon), the blood flow provided by the sigmoid arteries is critical for healing. The arteries deliver oxygen, nutrients, and immune cells that support tissue regeneration and repair at the surgical site.
Response to Inflammation: In cases of colitis or other inflammatory conditions affecting the sigmoid colon, the sigmoid arteries play a role in delivering immune cells to the affected areas. Adequate blood supply is necessary to support the immune response and promote healing in the inflamed tissues.

Role in Preventing Ischemia

The sigmoid arteries help prevent ischemic colitis, a condition caused by reduced blood flow to the colon, which can result in inflammation, ulceration, and tissue death. By maintaining a steady blood supply to the sigmoid colon and contributing to the collateral circulation via the marginal artery, the sigmoid arteries help ensure that the colon remains well-perfused, even if other arteries are compromised.

Ischemia Prevention through Collateral Circulation: The anastomoses formed by the sigmoid arteries with other arteries, such as the left colic and superior rectal arteries, allow for alternative pathways for blood flow. These anastomoses are particularly important in preventing ischemic injury to the colon in cases where the primary blood supply is reduced or obstructed.

Support for Colonic Motility and Defecation

The sigmoid arteries indirectly support the motility of the sigmoid colon and the process of defecation. By ensuring that the smooth muscle layers of the colon are well-oxygenated and functional, the arteries enable the rhythmic contractions that propel stool toward the rectum.

Colonic Motility: The sigmoid colon’s ability to contract and move fecal matter is dependent on the blood supply provided by the sigmoid arteries. This ensures that the colon’s muscles remain strong and capable of performing the peristaltic movements necessary for transporting stool.
Facilitation of Defecation: The sigmoid arteries support the final stages of digestion by enabling the sigmoid colon to push stool into the rectum for eventual elimination. Proper blood flow is essential for maintaining the colon’s motility and ensuring regular bowel movements.

Clinical Significance

The sigmoid arteries are clinically significant due to their role in supplying blood to the sigmoid colon, an essential part of the large intestine involved in the final stages of digestion and waste elimination. Disruption of blood flow through the sigmoid arteries, such as in cases of ischemic colitis, can lead to tissue damage, inflammation, and necrosis of the colon. This can result in symptoms such as abdominal pain, bleeding, and altered bowel habits, and may require surgical intervention if severe.

The sigmoid arteries also play a critical role during surgical procedures such as colectomy or sigmoidectomy, where preserving adequate blood supply is crucial for the healing of the remaining colon tissue. Their anastomoses with the left colic artery and superior rectal artery provide collateral circulation, which is important in maintaining blood flow to the colon when primary vessels are compromised. Damage or obstruction of the sigmoid arteries can lead to complications in colonic function and impede recovery after surgery.