Introduction
The aorta is the largest vessel of the body that transports blood from the heart to the rest of the body. It originates from the heart’s lower left chamber and moves down to the abdomen. The aortic arch, or the arch of the aorta, is a portion between the ascending and descending aorta. It distributes blood to the head and upper extremities of the body via three branches. The aortic arch also helps in maintaining blood pressure. This article gives insight into the particulars of the aortic arch.
What Is the Aortic Arch?
The aortic arch is a part of the aorta that transports blood to the upper extremities of the body and the head. It is present between the ascending and descending aorta. It distributes blood through three branches, namely, the left common carotid artery, the brachiocephalic trunk, and the left subclavian artery. The arch of the aorta forms during the fourth week of development and is derived from the left branch of the fourth pharyngeal arch. The lower part of the aortic arch in the fetus connects to the ductus arteriosus (a blood vessel that circulates blood around the fetal lungs before birth).
What Is the Structure of the Aortic Arch?
The aorta can be divided into four segments such as the ascending aorta, the arch of the aorta, the descending aorta or the thoracic aorta, and the abdominal aorta. The ascending aorta continues as the aortic arch till the second sternocostal joint. It courses superiorly, posteriorly, and to the left before continuing down as the abdominal aorta. The course of the aortic arch ends at the T4 vertebra (thoracic vertebra). Three branches arise from the aortic arch, including the left common carotid artery, the brachiocephalic trunk, and the left subclavian artery.
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Brachiocephalic Trunk - The brachiocephalic trunk is the largest branch from the aortic arch that ascends laterally and splits into the right common carotid and right subclavian arteries. The brachiocephalic trunk supplies the right side of the head and neck and the right upper limb.
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Left Common Carotid Artery - The left common carotid artery is the second branch, and it supplies the left side of the head and neck.
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Left Subclavian Artery - The left subclavian artery is the distal branch that supplies the left upper limb.
What Are the Functions of the Aortic Arch?
The aortic arch plays a vital role in blood pressure homeostasis. It maintains blood pressure via baroreceptors that are present on the walls of the arch of the aorta. The baroreceptors respond to the stretching of the aortic wall and transmit a signal to inhibit the sympathetic nervous system or activate the parasympathetic nervous system. This prevents changes in blood pressure.
The arch of the aorta also has peripheral chemoreceptors called aortic bodies. These receptors monitor the composition of blood, especially the partial pressure of oxygen and carbon monoxide. Changes in either of these gas levels stimulate signal transmission to the dorsal respiratory group in the brainstem through the vagus nerve. This stimulation regulates breathing.
What Are the Physiological Variations in the Aortic Arch?
Physiological variations are seen in the aortic arch, and its branches are seen in some individuals. It includes the following:
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The left common carotid artery may originate from the right brachiocephalic artery instead of the aortic arch.
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In some cases, the brachiocephalic artery and the common carotid artery of the left side may have a common origin.
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In rare cases, the brachiocephalic artery may give rise to the left common carotid artery and the left subclavian artery.
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In some individuals, a double aortic arch can be present and is associated with conditions like esophageal atresia or a congenital laryngeal web. A double aortic arch is diagnosed with a barium swallow, and a posterior indentation of the esophagus can be detected.
What Is Aortic Arch Syndrome?
The aortic arch syndrome is a condition in which a group of signs and symptoms are associated with structural deformities in the arteries that branch from the aortic arch. Trauma, blood clots, or developmental abnormalities can cause it. These defects affect the blood flow to the head, neck, or arms. Various types of aortic arch syndromes, including the absence of a branch of the aorta by birth, vascular rings, and isolation of the subclavian arteries, are seen in children. Takayasu syndrome is an inflammatory disease that affects women and girls and causes the narrowing of the vessels of the aortic arch. The aortic arch syndrome causes symptoms including breathing problems, blood pressure changes, dizziness, blurred vision, numbness of an arm, swallowing difficulties, decreased pulse rate, and transient ischemic attacks.
What Are the Considerations Followed During Aortic Arch Surgery?
An important surgical consideration is the avoidance of the left recurrent laryngeal nerve. It travels behind the aortic arch, loops around, and moves up in front of the aortic arch. Damage to the recurrent laryngeal nerve can cause vocal cord paralysis or voice hoarseness.
What Is the Clinical Significance of the Aortic Arch?
Aortic dissection is a dangerous complication that affects the aortic arch. It is an emergency condition in which a tear is present in the innermost layer of the aorta. Aortic dissection is the separation of the tunica intima (innermost layer) from the rest of the two layers of the aorta., which causes blood flow into the tunica media layer. Uncontrolled hypertension, atherosclerosis (hardening of the arteries), aortic aneurysms (weakening and bulging of the arteries), and aortic valve defects can cause aortic dissection. It can cause fatal complications like rupture of the aorta. The tear may extend into the aortic valve and cause regurgitation. Aortic arch dissection also reduces the blood flow to the upper extremities due to the blockage in one of the branches of the aortic arch.
Conclusion
The aortic arch, or the arch of the aorta, is a part of the aorta between the ascending and descending aorta. It distributes blood to the upper extremities of the body through its branches. It helps regulate breathing and maintain blood pressure homeostasis. It may present various physiological variants. The aortic arch in the great vessel is important as it maintains blood pressure and regulates breathing.
