The pericardiophrenic artery is a branch of the internal thoracic artery, which arises from the subclavian artery. This artery runs parallel to the phrenic nerve and plays a key role in supplying blood to the pericardium (the membrane surrounding the heart) and diaphragm.
Location
The pericardiophrenic artery originates from the internal thoracic artery in the upper part of the thoracic cavity. It descends through the thorax alongside the phrenic nerve, traveling between the pleura of the lungs and the pericardium. It runs vertically down the mediastinum, positioned close to the heart and diaphragm, until it reaches the diaphragm, where it contributes to the vascular supply of the diaphragm and surrounding tissues. The pericardiophrenic artery typically terminates near the diaphragm by anastomosing with branches of the musculophrenic artery and inferior phrenic artery.
Structure and Anatomy
Origin
The pericardiophrenic artery typically arises from the internal thoracic artery, a branch of the subclavian artery. The internal thoracic artery descends along the inner aspect of the thoracic wall, and the pericardiophrenic artery branches off near the upper part of the thoracic cavity, often at the level of the first or second intercostal space. It is one of the key arteries that supply the pericardium and diaphragm.
Course
After branching from the internal thoracic artery, the pericardiophrenic artery descends vertically through the thoracic cavity. It runs along the mediastinum, accompanying the phrenic nerve throughout its course. The artery travels in a parallel path with the phrenic nerve between the mediastinal pleura (the membrane covering the lungs) and the pericardium (the membrane enclosing the heart). This path places the pericardiophrenic artery in close proximity to both the heart and the lungs as it moves downward toward the diaphragm.
Relations
- Anteriorly: The pericardiophrenic artery is related to the sternum and the anterior thoracic wall, lying posterior to the inner surface of the thoracic cavity.
- Posteriorly: The artery is closely related to the pericardium, the fibrous sac surrounding the heart. It lies in the mediastinum between the heart and lungs.
- Medially: The artery is adjacent to the phrenic nerve, which it accompanies throughout its course, and runs parallel to the ascending aorta.
- Laterally: The artery is near the pleura, the membrane that covers the lungs.
Branches
The pericardiophrenic artery gives off small branches throughout its course that supply surrounding structures:
- Pericardial branches: These small branches supply the pericardium, ensuring adequate blood flow to the fibrous and serous layers of the pericardial membrane.
- Pleural branches: These branches provide blood to the mediastinal pleura, which lines the thoracic cavity.
- Diaphragmatic branches: As the artery approaches the diaphragm, it gives off branches that contribute to the blood supply of the diaphragm.
Termination
The pericardiophrenic artery typically terminates by anastomosing with other arteries that supply the diaphragm, including the musculophrenic artery (another branch of the internal thoracic artery) and the inferior phrenic artery (a branch of the abdominal aorta). These anastomoses form a network of vessels that ensure the diaphragm receives an adequate blood supply for its essential respiratory function.
Anastomoses
The pericardiophrenic artery forms important anastomoses with other arteries that also supply the diaphragm and the pericardium:
- Musculophrenic artery: This artery, which is a terminal branch of the internal thoracic artery, assists in providing blood to the diaphragm.
- Inferior phrenic artery: This artery, originating from the abdominal aorta, anastomoses with the pericardiophrenic artery at the diaphragm, contributing to the vascular network that supplies the muscle.
- Bronchial and esophageal arteries: In some cases, the pericardiophrenic artery may form small anastomoses with these arteries, which also supply nearby structures in the thoracic cavity.
Variations
Anatomical variations in the course and branching pattern of the pericardiophrenic artery are rare but can occur. In some individuals, the artery may have a slightly different origin or may give rise to additional small branches that supply nearby structures, such as the thoracic wall or mediastinum. In rare cases, variations in the size of the artery may influence its contribution to the blood supply of the pericardium and diaphragm.
Function
The pericardiophrenic artery plays a crucial role in supplying blood to the thoracic structures, particularly the pericardium and diaphragm. It also contributes to the vascularization of the mediastinum and pleura. By ensuring proper blood flow to these areas, the artery supports key physiological functions such as respiration and cardiac protection. Below is a detailed explanation of its primary functions.
Blood Supply to the Pericardium
The most important function of the pericardiophrenic artery is to provide oxygenated blood to the pericardium, which is the fibrous sac that encloses the heart. The pericardium consists of two layers: the fibrous pericardium and the serous pericardium. The pericardiophrenic artery supplies the outer fibrous layer, which acts as a protective covering for the heart. Proper blood supply is essential for maintaining the health of the pericardium, as it needs to remain elastic and strong to protect the heart and prevent overstretching during cardiac cycles. The artery helps nourish this membrane and allows it to support the heart’s movements without friction.
Blood Supply to the Diaphragm
The pericardiophrenic artery contributes significantly to the vascularization of the diaphragm, the primary muscle involved in respiration. The diaphragm separates the thoracic cavity from the abdominal cavity and contracts during inhalation to allow the lungs to expand. The pericardiophrenic artery, in combination with the musculophrenic and inferior phrenic arteries, supplies the superior portion of the diaphragm, providing the muscle with the oxygen and nutrients it needs for continuous contraction and relaxation during breathing.
This blood supply is essential for the diaphragm’s endurance and function, as it constantly works throughout life. Without adequate blood flow, the diaphragm’s ability to perform efficiently would be compromised, leading to difficulties in breathing.
Blood Supply to the Mediastinal Pleura
The pericardiophrenic artery also supplies the mediastinal pleura, which is the portion of the pleura (the membrane that covers the lungs) that lines the mediastinum, the central compartment of the thoracic cavity. The pleura allows the lungs to move smoothly within the thoracic cavity as they expand and contract during respiration. The branches of the pericardiophrenic artery ensure that this membrane remains healthy and lubricated, allowing for frictionless movement of the lungs and protecting the surrounding structures.
Support for Collateral Circulation in the Thoracic Cavity
The pericardiophrenic artery contributes to the broader network of collateral circulation within the thoracic cavity. It forms anastomoses with other important arteries, including the musculophrenic artery, which also branches from the internal thoracic artery, and the inferior phrenic artery, which arises from the abdominal aorta. This anastomotic network ensures that the pericardium, diaphragm, and pleura receive adequate blood supply, even in cases of vascular compromise.
For example, if the main blood flow through the internal thoracic artery is obstructed or diminished due to trauma, surgery, or disease, the anastomoses between the pericardiophrenic artery and other arteries help maintain blood flow to the diaphragm and pericardium, preventing ischemia and ensuring the continued function of these structures.
Support for the Phrenic Nerve
Although the pericardiophrenic artery primarily supplies the pericardium and diaphragm, its close anatomical relationship with the phrenic nerve may also have functional significance. The phrenic nerve is responsible for innervating the diaphragm, and the pericardiophrenic artery runs alongside it throughout its course in the thoracic cavity. This close association ensures that the phrenic nerve is in proximity to an adequate blood supply, which is important for its health and function in transmitting signals that control diaphragm movement during respiration.
Contribution to Thoracic Tissue Health
Through its branches and collateral circulation, the pericardiophrenic artery helps maintain the overall health of the thoracic tissues, including the pericardium, diaphragm, pleura, and mediastinal structures. Adequate blood flow to these tissues is necessary for proper healing, regeneration, and function, especially in the case of injury or surgery. For instance, during thoracic surgeries, such as cardiac procedures or lung resections, the pericardiophrenic artery plays a role in supplying blood to the pericardium and diaphragm, ensuring these structures remain functional and resilient throughout the recovery process.
Clinical Significance
The pericardiophrenic artery is clinically significant due to its role in supplying blood to the pericardium, diaphragm, and mediastinal pleura. It is particularly important during thoracic surgeries such as cardiac procedures, where the artery may be at risk of injury, leading to complications such as bleeding or compromised blood supply to the diaphragm and pericardium. Maintaining its integrity is crucial for postoperative recovery, especially in cases involving the heart or lungs.
The artery’s close association with the phrenic nerve is another key clinical aspect. Damage to either the artery or the phrenic nerve during surgery could lead to diaphragmatic dysfunction, resulting in breathing difficulties or diaphragmatic paralysis. Its contribution to collateral circulation with other arteries, such as the musculophrenic and inferior phrenic arteries, helps ensure continued blood flow to the diaphragm and pericardium, even if one of the other arteries is compromised. Understanding its anatomy is vital for thoracic surgeons to avoid complications and ensure the effective functioning of these critical thoracic structures.
