The brachiocephalic trunk, also known as the innominate artery, is a short blood vessel located in the upper chest. It serves as the primary conduit for oxygenated blood to the right side of the head, neck, and right upper limb. As the largest and first branch to emerge from the aortic arch, it plays a unique role in the circulatory system. This artery is approximately 4 to 5 centimeters long and is a singular structure, with no corresponding trunk on the left side of the body.
Anatomical Position and Origin
The brachiocephalic trunk originates directly from the aortic arch, the curved segment of the aorta high in the chest. It is situated within the superior mediastinum, the upper central compartment of the chest cavity that also houses the trachea, esophagus, and several major veins and nerves. The artery courses upward and obliquely to the right, beginning deep behind the manubrium, the upper part of the sternum. This wide vessel lies just anterior to the trachea, crossing it from the left side to the right as it ascends. Its proximity to the trachea is important in surgical contexts.
The brachiocephalic trunk terminates just behind the right sternoclavicular joint, the articulation between the collarbone and the sternum. The vessels supplying the left side of the body originate separately from the aortic arch. The left common carotid artery and the left subclavian artery arise directly from the arch, whereas their counterparts on the right side are combined into the single brachiocephalic trunk.
The Essential Branches
The brachiocephalic trunk quickly divides into two major terminal branches, ensuring the delivery of oxygen-rich blood to the upper right quadrant of the body. The trunk’s bifurcation occurs at the level of the right sternoclavicular joint. This split creates the right common carotid artery and the right subclavian artery.
The right common carotid artery travels superiorly into the neck to supply the head and neck region. It is responsible for carrying blood to the right side of the brain, face, and other structures in the head.
The second branch is the right subclavian artery, which routes laterally toward the right arm. This artery primarily provides blood flow to the right upper limb, including the shoulder, arm, and hand. The subclavian artery also gives off the vertebral artery, a vessel that travels up toward the brain to contribute to the blood supply of the posterior brain circulation.
Medical Significance of the Trunk
Brachiocephalic Stenosis
Because of its position as the single gateway for blood flow to the entire right upper body and parts of the brain, the health of the brachiocephalic trunk has considerable medical significance. One common issue is brachiocephalic stenosis, which is a narrowing of the artery, typically caused by the buildup of atherosclerotic plaque. This narrowing reduces the volume and pressure of blood flowing to the right arm and the right side of the brain.
Symptoms of stenosis can include transient ischemic attacks (TIAs), or mini-strokes, and visual disturbances due to reduced blood flow to the brain. Patients may also experience arm claudication, which is pain or cramping in the right upper extremity, especially during movement or exercise. Stenosis can be treated with endovascular procedures, such as angioplasty and stenting, which are minimally invasive techniques used to open the blocked vessel.
Subclavian Steal Syndrome
A more complex condition that can arise from severe stenosis is Subclavian Steal Syndrome. When the blockage is severe enough, the blood flow to the right arm can be compromised, causing the body to reroute blood from the right vertebral artery, which normally supplies the brain. This reversal of flow, or “stealing” of blood intended for the brain, can cause neurological symptoms like dizziness, vertigo, or slurred speech, particularly when the arm is being exercised.
Aneurysms and Surgical Importance
Given its high-pressure origin directly off the aortic arch, the brachiocephalic trunk is also susceptible to aneurysms, which are abnormal bulges in the vessel wall, and arterial dissection, a life-threatening tear in the inner layer of the artery. Due to the trunk’s short length and location near the heart, these conditions require immediate and complex surgical or endovascular intervention.
The artery is a frequent landmark in thoracic surgery, particularly in procedures involving the aortic arch. Surgeons must identify and manage its branches to maintain blood supply to the head and arm.