The aortic arch, arch of the aorta, or transverse aortic arch () is the part of the

aorta The aorta ( ) is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes o ...

between the ascending and

descending aorta In human anatomy, the descending aorta is part of the aorta, the largest artery in the body. The descending aorta begins at the aortic arch and runs down through the chest and abdomen. The descending aorta anatomically consists of two portions o ...

. The arch travels backward, so that it ultimately runs to the left of the

trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from the ...

Structure

The aorta begins at the level of the upper border of the second/third

sternocostal articulation The sternocostal joints, also known as sternochondral joints or costosternal articulations, are synovial plane joints of the costal cartilages of the true ribs with the sternum. The only exception is the first rib, which has a synchondrosis joi ...

of the right side, behind the

ventricular outflow tract A ventricular outflow tract is a portion of either the left ventricle or right ventricle of the heart through which blood passes in order to enter the great arteries. The right ventricular outflow tract (RVOT) is an infundibular extension of ...

and

pulmonary trunk A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The largest pulmonary artery is the ''main pulmonary artery'' or ''pulmonary trunk'' from the heart, and ...

. The right atrial appendage overlaps it. The first few centimeters of the ascending aorta and pulmonary trunk lies in the same pericardial sheath. and runs at first upward, arches over the

right pulmonary artery A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The largest pulmonary artery is the ''main pulmonary artery'' or ''pulmonary trunk'' from the heart, and ...

, and

right main bronchus A bronchus is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi pronounced (BRAN-KAI) to branch from the trachea at the carina are the right main bronchus and the left main bronch ...

to lie behind the right second coastal cartilage. The right lung and sternum lies anterior to the aorta at this point. The aorta then passes posteriorly and to the left, anterior to the trachea, and arches over

left main bronchus A bronchus is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi pronounced (BRAN-KAI) to branch from the trachea at the carina are the right main bronchus and the left main bronch ...

and

left pulmonary artery A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The largest pulmonary artery is the ''main pulmonary artery'' or ''pulmonary trunk'' from the heart, and ...

, and reaches to the left side of the T4 vertebral body. Apart from T4 vertebral body, other structures such as trachea, oesophagus, and

thoracic duct In human anatomy, the thoracic duct is the larger of the two lymph ducts of the lymphatic system. It is also known as the ''left lymphatic duct'', ''alimentary duct'', ''chyliferous duct'', and ''Van Hoorne's canal''. The other duct is the righ ...

(from front to back) also lies to the left of the aorta. Inferiorly, the arch of aorta is connected to

ligamentum arteriosum The ligamentum arteriosum (arterial ligament), also known as the Ligament of Botallo or Harvey's ligament, is a small ligament attaching the aorta to the pulmonary artery. It serves no function in adults but is the remnant of the ductus arteriosus ...

while superiorly, it gives rise to three main branches. Arch of aorta continues as the

after T4 vertebral body. The aortic arch has three main branches on its superior aspect. The first, and largest, branch of the arch of the aorta is the

brachiocephalic trunk The brachiocephalic artery (or brachiocephalic trunk or innominate artery) is an artery of the mediastinum that supplies blood to the right arm and the head and neck. It is the first branch of the aortic arch. Soon after it emerges, the brachi ...

, which is to the right and slightly anterior to the other two branches and originates behind the manubrium of the sternum. Next, the

left common carotid artery In anatomy, the left and right common carotid arteries (carotids) (Entry "carotid"
in
left subclavian artery comes off of the aortic arch to the left of the left common carotid artery and ascends, with the left common carotid, through the superior mediastinum and along the left side of the trachea. An anatomical variation is that the left

vertebral artery The vertebral arteries are major arteries of the neck. Typically, the vertebral arteries originate from the subclavian arteries. Each vessel courses superiorly along each side of the neck, merging within the skull to form the single, midline ba ...

can arise from the aortic arch instead of the left subclavian artery. The arch of the aorta forms two curvatures: one with its convexity upward, the other with its convexity forward and to the left. Its upper border is usually about 2.5 cm. below the superior border to the manubrium sterni. Blood flows from the upper curvature to the upper regions of the body, located above the heart - namely the arms, neck, and head. Coming out of the heart, the thoracic aorta has a maximum diameter of 40 mm at the root. By the time it becomes the ascending aorta, the diameter should be < 35–38 mm, and 30 mm at the arch. The diameter of the descending aorta should not exceed 25 mm. The arch of the aorta lies within the mediastinum. At the cellular level, the aorta and the aortic arch are composed of three layers: The

tunica intima The tunica intima (New Latin "inner coat"), or intima for short, is the innermost tunica (layer) of an artery or vein. It is made up of one layer of endothelial cells and is supported by an internal elastic lamina. The endothelial cells are i ...

, which surrounds the lumen and is composed of simple squamal epithelial cells; the

tunica media The tunica media (New Latin "middle coat"), or media for short, is the middle tunica (layer) of an artery or vein. It lies between the tunica intima on the inside and the tunica externa on the outside. Artery Tunica media is made up of smooth ...

, composed of smooth cell muscles and elastic fibers; and, the

tunica adventitia The tunica externa (New Latin "outer coat"), also known as the tunica adventitia (New Latin "additional coat"), is the outermost tunica (layer) of a blood vessel, surrounding the tunica media. It is mainly composed of collagen and, in arteries, i ...

, composed of loose collagen fibers. Innervated by

barometric A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...

nerve terminals, the aortic arch is responsible for sensing changes in the dilation of the vascular walls, inducing changes in heart rate to compensate for changes in blood pressure.

Development

The aortic arch is the connection between the ascending and descending aorta, and its central part is formed by the left 4th

aortic arch The aortic arch, arch of the aorta, or transverse aortic arch () is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of the trachea. Structure The aorta begins ...

during early development. The

ductus arteriosus The ''ductus arteriosus'', also called the ''ductus Botalli'', named after the Italian physiologist Leonardo Botallo, is a blood vessel in the developing fetus connecting the trunk of the pulmonary artery to the proximal descending aorta. It a ...

connects to the lower part of the arch in foetal life. This allows blood from the right ventricle to mostly bypass the pulmonary vessels as they develop. The final section of the aortic arch is known as the aortic isthmus. This is so called because it is a narrowing (

isthmus An isthmus (; ; ) is a narrow piece of land connecting two larger areas across an expanse of water by which they are otherwise separated. A tombolo is an isthmus that consists of a spit or bar, and a strait is the sea counterpart of an isthmus ...

) of the aorta as a result of decreased blood flow when in foetal life. As the

left ventricle A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood towards the peripheral beds within the body and lungs. The blood pumped by a ventricle is supplied by an atrium, an adjacent chamber in the uppe ...

of the heart increases in size throughout life, the narrowing eventually dilates to become a normal size. If this does not occur, this can result in

coarctation of the aorta Coarctation of the aorta (CoA or CoAo), also called aortic narrowing, is a congenital condition whereby the aorta is narrow, usually in the area where the ductus arteriosus (ligamentum arteriosum after regression) inserts. The word ''coarctation' ...

. The

connects to the final section of the arch in foetal life. Ductus arteriosus then regresses to become

during later life.

Variation

There are three common variations in how arteries branch from the aortic arch. In about 75% of individuals, the branching is "normal", as described above. In some individuals the left common carotid artery originates from the brachiocephalic artery rather than the aortic arch. In others, the brachiocephalic artery and left common carotid artery share an origin. This variant is found in approximately a 20% of the population. In a third variant, the brachiocephalic artery splits into three arteries: the left common carotid artery, the right common carotid artery and the right subclavian artery; this variant is found in an estimated 7% of individuals. In rare cases, the

thyroid ima artery The thyroid ima artery (thyroidea ima artery, ''arteria thyroidea ima'', thyroid artery of Neubauer or the lowest thyroid artery) is an artery of the head and neck. It is an anatomical variant that, when present, supplies blood to the thyroid gl ...

, a variant artery supplying the thyroid gland may arise from the aortic arch.

Clinical significance

The ''aortic knob'' is the prominent shadow of the aortic arch on a frontal chest radiograph.wrongdiagnosis.com > Aortic knob
Citing: Stedman's Medical Spellchecker, 2006 Lippincott Williams & Wilkins. Aortopexy is a surgical procedure in which the aortic arch is fixed to the

sternum The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Sha ...

in order to keep the

open. Aortic isthmus is the relatively fixed part of the aortic arch. It is prone to

shearing force In solid mechanics, shearing forces are unaligned forces acting on one part of a body in a specific direction, and another part of the body in the opposite direction. When the forces are collinear (aligned with each other), they are called ...

and trauma that can cause it to tear and result in massive bleeding.

Additional images

Image:Gray490.png, The arch of aorta can be seen here, with the lungs to either side and emerging from the

heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to t ...

, below. Image:Gray793.png, A branch of the

vagus nerve The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and righ ...

, the

recurrent laryngeal nerve The recurrent laryngeal nerve (RLN) is a branch of the vagus nerve ( cranial nerve X) that supplies all the intrinsic muscles of the larynx, with the exception of the cricothyroid muscles. There are two recurrent laryngeal nerves, right and ...

, passes underneath the arch of aorta. The nerve is seen here.

References

External links

Anatomy Teaching Case from MedPix {{DEFAULTSORT:Aortic Arch Arteries of the thorax arch