The aorta (/eɪˈɔːrtə/ ay-OR-tə) 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 oxygenated blood to all parts of the body through the systemic circulation.
Schematic view of the aorta and its segments
Branches of the aorta
|Precursor||Truncus arteriosus Fourth left branchial artery Paired dorsal aortae (combine into the single descending aorta)|
Arch of aorta (supra-aortic vessels):
Descending aorta, thoracic part:
Descending aorta, abdominal part:
|Vein||Combination of coronary sinus, superior vena cava and inferior vena cava|
|Supplies||The systemic circulation|
(entire body with exception of the respiratory zone of the lung which is supplied by the pulmonary circulation)
|Latin||Aorta, arteria maxima|
One way of classifying a part of the aorta is by anatomical compartment, where the thoracic aorta (or thoracic portion of the aorta) runs from the heart to the diaphragm. The aorta then continues downward as the abdominal aorta (or abdominal portion of the aorta) diaphragm to the aortic bifurcation.
Another system divides the aorta with respect to its course and the direction of blood flow. In this system, the aorta starts as the ascending aorta then travels superiorly from the heart and then makes a hairpin turn known as the aortic arch. Following the aortic arch, the aorta then travels inferiorly as the descending aorta. The descending aorta has two parts. The aorta begins to descend in the thoracic cavity, and consequently is known as the thoracic aorta. After the aorta passes through the diaphragm, it is known as the abdominal aorta. The aorta ends by dividing into two major blood vessels, the common iliac arteries and a smaller midline vessel, the median sacral artery.:18
The ascending aorta begins at the opening of the aortic valve in the left ventricle of the heart. It runs through a common pericardial sheath with the pulmonary trunk. These two blood vessels twist around each other, causing the aorta to start out posterior to the pulmonary trunk, but end by twisting to its right and anterior side.:191,204 The transition from ascending aorta to aortic arch is at the pericardial reflection on the aorta.:Plate 211
At the root of the ascending aorta, the lumen has three small pockets between the cusps of the aortic valve and the wall of the aorta, which are called the aortic sinuses or the sinuses of Valsalva. The left aortic sinus contains the origin of the left coronary artery and the right aortic sinus likewise gives rise to the right coronary artery. Together, these two arteries supply the heart. The posterior aortic sinus does not give rise to a coronary artery. For this reason the left, right and posterior aortic sinuses are also called left-coronary, right-coronary and non-coronary sinuses.:191
The aortic arch loops over the left pulmonary artery and the bifurcation of the pulmonary trunk, to which it remains connected by the ligamentum arteriosum, a remnant of the fetal circulation that is obliterated a few days after birth. In addition to these blood vessels, the aortic arch crosses the left main bronchus. Between the aortic arch and the pulmonary trunk is a network of autonomic nerve fibers, the cardiac plexus or aortic plexus. The left vagus nerve, which passes anterior to the aortic arch, gives off a major branch, the recurrent laryngeal nerve, which loops under the aortic arch just lateral to the ligamentum arteriosum. It then runs back to the neck.
The aortic arch has three major branches: from proximal to distal, they are the brachiocephalic trunk, the left common carotid artery, and the left subclavian artery. The brachiocephalic trunk supplies the right side of the head and neck as well as the right arm and chest wall, while the latter two together supply the left side of the same regions.
The thoracic descending aorta gives rise to the intercostal and subcostal arteries, as well as to the superior and inferior left bronchial arteries and variable branches to the esophagus, mediastinum, and pericardium. Its lowest pair of branches are the superior phrenic arteries, which supply the diaphragm, and the subcostal arteries for the twelfth rib.:195
The abdominal aorta begins at the aortic hiatus of the diaphragm at the level of the twelfth thoracic vertebra. It gives rise to lumbar and musculophrenic arteries, renal and middle suprarenal arteries, and visceral arteries (the celiac trunk, the superior mesenteric artery and the inferior mesenteric artery). It ends in a bifurcation into the left and right common iliac arteries. At the point of the bifurcation, there also springs a smaller branch, the median sacral artery.:331
The ascending aorta develops from the outflow tract which initially starts as a single tube connecting the heart with the aortic arches (which will form the great arteries) in early development, but then is separated into the aorta and the pulmonary trunk.
The aortic arches start as five pairs of symmetrical arteries connecting the heart with the dorsal aorta, and then undergo a significant remodelling to form the final asymmetrical structure of the great arteries, with the 3rd pair of arteries contributing to the common carotids, the right 4th forming the base and middle part of the right subclavian artery and the left 4th being the central part of the aortic arch. The smooth muscle of the great arteries and the population of cells that form the aorticopulmonary septum that separates the aorta and pulmonary artery is derived from cardiac neural crest. This contribution of the neural crest to the great artery smooth muscle is unusual as most smooth muscle is derived from mesoderm. In fact the smooth muscle within the abdominal aorta is derived from mesoderm, and the coronary arteries, which arise just above the semilunar valves, possess smooth muscle of mesodermal origin. A failure of the aorticopulmonary septum to divide the great vessels results in persistent truncus arteriosus.
The aorta is an elastic artery, and as such is quite distensible. The aorta consists of a heterogeneous mixture of smooth muscle, nerves, intimal cells, endothelial cells, fibroblast-like cells, and a complex extracellular matrix. The vascular wall consists of several layers known as the tunica externa, tunica media, and tunica intima. The thickness of the aorta requires an extensive network of tiny blood vessels called vasa vasorum, which feed the tunica externa and tunica media outer layers of the aorta. The aortic arch contains baroreceptors and chemoreceptors that relay information concerning blood pressure and blood pH and carbon dioxide levels to the medulla oblongata of the brain. This information is processed by the brain and the autonomic nervous system mediates the homeostatic responses.
Within the tunica media, smooth muscle and the extracellular matrix are quantitatively the largest components of the aortic vascular wall. The fundamental unit of the aorta is the elastic lamella, which consists of smooth muscle and elastic matrix. The medial layer of the aorta consist of concentric musculoelastic layers (the elastic lamella) in mammals. The smooth muscle component does not dramatically alter the diameter of the aorta but rather serves to increase the stiffness and viscoelasticity of the aortic wall when activated. The elastic matrix dominates the biomechanical properties of the aorta. The elastic matrix forms lamellae, consisting of elastic fibers, collagens (predominately type III), proteoglycans, and glycoaminoglycans.
Variations may occur in the location of the aorta, and the way in which arteries branch off the aorta. The aorta, normally on the left side of the body, may be found on the right in dextrocardia, in which the heart is found on the right, or situs inversus, in which the location of all organs are flipped.:188
The aorta supplies all of the systemic circulation, which means that the entire body, except for the respiratory zone of the lung, receives its blood from the aorta. Broadly speaking, branches from the ascending aorta supply the heart; branches from the aortic arch supply the head, neck and arms; branches from the thoracic descending aorta supply the chest (excluding the heart and the respiratory zone of the lung); and branches from the abdominal aorta supply the abdomen. The pelvis and legs get their blood from the common iliac arteries.
The pulsatile nature of blood flow creates a pulse wave that is propagated down the arterial tree, and at bifurcations reflected waves rebound to return to semilunar valves and the origin of the aorta. These return waves create the dicrotic notch displayed in the aortic pressure curve during the cardiac cycle as these reflected waves push on the aortic semilunar valve. With age, the aorta stiffens such that the pulse wave is propagated faster and reflected waves return to the heart faster before the semilunar valve closes, which raises the blood pressure. The stiffness of the aorta is associated with a number of diseases and pathologies, and noninvasive measures of the pulse wave velocity are an independent indicator of hypertension. Measuring the pulse wave velocity (invasively and non-invasively) is a means of determining arterial stiffness. Maximum aortic velocity may be noted as Vmax or less commonly as AoVmax.
Mean arterial pressure (MAP) is highest in the aorta and the MAP decreases across the circulation from aorta to arteries to arterioles to capillaries to veins back to atrium. The difference between aortic and right atrial pressure accounts for blood flow in the circulation. When the left ventricle contracts to force blood into the aorta, the aorta expands. This stretching gives the potential energy that will help maintain blood pressure during diastole, as during this time the aorta contracts passively. This Windkessel effect of the great elastic arteries has important biomechanical implications. The elastic recoil helps conserve the energy from the pumping heart and smooth out the pulsatile nature created by the heart. Aortic pressure is highest at the aorta and becomes less pulsatile and lower pressure as blood vessels divide into arteries, arterioles, and capillaries such that flow is slow and smooth for gases and nutrient exchange.
All amniotes have a broadly similar arrangement to that of humans, albeit with a number of individual variations. In fish, however, there are two separate vessels referred to as aortas. The ventral aorta carries de-oxygenated blood from the heart to the gills; part of this vessel forms the ascending aorta in tetrapods (the remainder forms the pulmonary artery). A second, dorsal aorta carries oxygenated blood from the gills to the rest of the body, and is homologous with the descending aorta of tetrapods. The two aortas are connected by a number of vessels, one passing through each of the gills. Amphibians also retain the fifth connecting vessel, so that the aorta has two parallel arches.
The word 'Aorta' stems from the Late Latin aorta from Classical Greek aortē (ἀορτή), from aeirō, "I lift, raise" (ἀείρω) This term was first applied by Aristotle when describing the aorta and describes accurately how it seems to be 'suspended' above the heart.
The abdominal aorta is the largest artery in the abdominal cavity. As part of the aorta, it is a direct continuation of the descending aorta (of the thorax).Aneurysm
An aneurysm is an outward bulging, likened to a bubble or balloon, caused by a localized, abnormal, weak spot on a blood vessel wall. Aneurysms are a result of a weakened blood vessel wall, and may be a result of a hereditary condition or an acquired disease. Aneurysms can also be a nidus (starting point) for clot formation (thrombosis) and embolization. The word is from Greek: ἀνεύρυσμα, aneurysma, "dilation", from ἀνευρύνειν, aneurynein, "to dilate". As an aneurysm increases in size, the risk of rupture increases, leading to uncontrolled bleeding. Although they may occur in any blood vessel, particularly lethal examples include aneurysms of the Circle of Willis in the brain, aortic aneurysms affecting the thoracic aorta, and abdominal aortic aneurysms. Aneurysms can arise in the heart itself following a heart attack, including both ventricular and atrial septal aneurysms.Aortic aneurysm
An aortic aneurysm is an enlargement (dilatation) of the aorta to greater than 1.5 times normal size. They usually cause no symptoms except when ruptured. Occasionally, there may be abdominal, back, or leg pain.They are most commonly located in the abdominal aorta, but can also be located in the thoracic aorta. Aortic aneurysms cause weakness in the wall of the aorta and increase the risk of aortic rupture. When rupture occurs, massive internal bleeding results and, unless treated immediately, shock and death can occur.
Screening with ultrasound is indicated in those at high risk. Prevention is by decreasing risk factors, such as smoking, and treatment is either by open or endovascular surgery. Aortic aneurysms resulted in about 152,000 deaths worldwide in 2013, up from 100,000 in 1990.Aortic arch
The aortic arch, arch of the aorta, or transverse aortic arch (English: ) 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.Aortic dissection
Aortic dissection (AD) occurs when an injury to the innermost layer of the aorta allows blood to flow between the layers of the aortic wall, forcing the layers apart. In most cases, this is associated with a sudden onset of severe chest or back pain, often described as "tearing" in character. Also, vomiting, sweating, and lightheadedness may occur. Other symptoms may result from decreased blood supply to other organs, such as stroke or mesenteric ischemia. Aortic dissection can quickly lead to death from not enough blood flow to the heart or complete rupture of the aorta.AD is more common in those with a history of high blood pressure, a number of connective tissue diseases that affect blood vessel wall strength including Marfan syndrome and Ehlers Danlos syndrome, a bicuspid aortic valve, and previous heart surgery. Major trauma, smoking, cocaine use, pregnancy, a thoracic aortic aneurysm, inflammation of arteries, and abnormal lipid levels are also associated with an increased risk. The diagnosis is suspected based on symptoms with medical imaging, such as computed tomography, magnetic resonance imaging, or ultrasound used to confirm and further evaluate the dissection. The two main types are Stanford type A, which involves the first part of the aorta, and type B, which does not.Prevention is by blood pressure control and not smoking. Management of AD depends on the part of the aorta involved. Dissections that involve the first part of the aorta usually require surgery. Surgery may be done either by an opening in the chest or from inside the blood vessel. Dissections that involve the second part of the aorta can typically be treated with medications that lower blood pressure and heart rate, unless there are complications.AD is relatively rare, occurring at an estimated rate of three per 100,000 people per year. It is more common in males than females. The typical age at diagnosis is 63, with about 10% of cases occurring before the age of 40. Without treatment, about half of people with Stanford type A dissections die within three days and about 10% of people with Stanford type B dissections die within one month. The first case of AD was described in the examination of King George II of Great Britain following his death in 1760. Surgery for AD was introduced in the 1950s by Michael E. DeBakey.Aortic stenosis
Aortic stenosis (AS or AoS) is the narrowing of the exit of the left ventricle of the heart (where the aorta begins), such that problems result. It may occur at the aortic valve as well as above and below this level. It typically gets worse over time. Symptoms often come on gradually with a decreased ability to exercise often occurring first. If heart failure, loss of consciousness, or heart related chest pain occurs due to AS the outcomes are worse. Loss of consciousness typically occurs with standing or exercise. Signs of heart failure include shortness of breath especially when lying down, at night, or with exercise, and swelling of the legs. Thickening of the valve without narrowing is known as aortic sclerosis.Causes include being born with a bicuspid aortic valve, and rheumatic fever. A bicuspid aortic valve affects about one to two percent of the population. As of 2014 rheumatic heart disease mostly occurs in the developing world. A normal valve may also harden over the decades. Risk factors are similar to those of coronary artery disease and include smoking, high blood pressure, high cholesterol, diabetes, and being male. The aortic valve usually has three leaflets and is located between the left ventricle of the heart and the aorta. AS typically results in a heart murmur. Its severity can be divided into mild, moderate, severe, and very severe, distinguishable by ultrasound of the heart.Aortic stenosis is typically followed using repeated ultrasound scans. Once it has become severe, treatment primarily involves valve replacement surgery, with transcatheter aortic valve replacement (TAVR) being an option in some who are at high risk from surgery. Valves may either be mechanical or bioprosthetic, with each having risks and benefits. Another less invasive procedure, balloon aortic valvuloplasty (BAV), may result in benefit, but for only a few months. Complications such as heart failure may be treated in the same way as in those with mild to moderate AS. In those with severe disease a number of medications should be avoided, including ACE inhibitors, nitroglycerin, and some beta blockers. Nitroprusside or phenylephrine may be used in those with decompensated heart failure depending on the blood pressure.Aortic stenosis is the most common valvular heart disease in the developed world. It affects about 2% of people who are over 65 years of age. Estimated rates were not known in most of the developing world as of 2014. In those who have symptoms, without repair the chance of death at five years is about 50% and at 10 years is about 90%. Aortic stenosis was first described by French physician Lazare Rivière in 1663.Aortic valve
The aortic valve is a valve in the human heart between the left ventricle and the aorta. It is one of the two semilunar valves of the heart, the other being the pulmonary valve. The heart has four valves and the other two are the mitral and the tricuspid valves. The aortic valve normally has three cusps or leaflets, although in 1–2% of the population it is found to congenitally have two leaflets. The aortic valve is the last structure in the heart the blood travels through before flowing through the systemic circulation.Aortography
Aortography involves placement of a catheter in the aorta and injection of contrast material while taking X-rays of the aorta. The procedure is known as an aortogram. The diagnosis of aortic dissection can be made by visualization of the intimal flap and flow of contrast material in both the true lumen and the false lumen. The catheter has to be inserted through the right femoral artery, because in about two thirds of cases the aortic dissection spreads into the left common iliac artery.
The aortogram was previously considered the gold standard test for the diagnosis of aortic dissection, with a sensitivity of up to 80% and a specificity of about 94%. It is especially poor in the diagnosis of cases where the dissection is due to hemorrhage within the media without any initiating intimal tear.
The advantage of the aortogram in the diagnosis of aortic dissection is that it can delineate the extent of involvement of the aorta and branch vessels and can diagnose aortic insufficiency. The disadvantages of the aortogram are that it is an invasive procedure and it requires the use of iodinated contrast material.Aortography has largely been replaced by the diagnostic tools of MRI, CT, and transesophageal echocardiography (TEE) all of which have high sensitivities. TEE is favored in emergency situations, as it is relatively non-invasive and a rapid procedure (more so than MRI, which can takes hours).Aortoiliac occlusive disease
In medicine, aortoiliac occlusive disease, also known as Leriche's syndrome and Leriche syndrome, is a form of central artery disease involving the blockage of the abdominal aorta as it transitions into the common iliac arteries.Ascending aorta
The ascending aorta (AAo) is a portion of the aorta commencing at the upper part of the base of the left ventricle, on a level with the lower border of the third costal cartilage behind the left half of the sternum.Bicuspid aortic valve
Bicuspid aortic valve (BAV) is an inherited form of heart disease in which two of the leaflets of the aortic valve fuse during development in the womb resulting in a two-leaflet valve (bicuspid valve) instead of the normal three-leaflet valve (tricuspid). BAV is the most common cause of heart disease present at birth and affects approximately 1.3% of adults. Normally, the mitral valve is the only bicuspid valve and this is situated between the heart's left atrium and left ventricle. Heart valves play a crucial role in ensuring the unidirectional flow of blood from the atrium to the ventricles, or from the ventricle to the aorta or pulmonary trunk.Celiac artery
The celiac (or coeliac; ) artery, also known as the celiac trunk, or truncus coeliacus, is the first major branch of the abdominal aorta.
It is 1.25 cm in length.
Branching from the aorta at thoracic vertebra 12 (T12) in humans, it is one of three anterior/ midline branches of the abdominal aorta (the others are the superior and inferior mesenteric arteries).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" means narrowing. Coarctations are most common in the aortic arch. The arch may be small in babies with coarctations. Other heart defects may also occur when coarctation is present, typically occurring on the left side of the heart. When a patient has a coarctation, the left ventricle has to work harder. Since the aorta is narrowed, the left ventricle must generate a much higher pressure than normal in order to force enough blood through the aorta to deliver blood to the lower part of the body. If the narrowing is severe enough, the left ventricle may not be strong enough to push blood through the coarctation, thus resulting in lack of blood to the lower half of the body. Physiologically its complete form is manifested as interrupted aortic arch.Descending aorta
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 or segments, the thoracic and the abdominal aorta, in correspondence with the two great cavities of the trunk in which it is situated. Within the abdomen, the descending aorta branches into the two common iliac arteries which serve the pelvis and eventually legs.
The ductus arteriosus connects to the junction between the pulmonary artery and the descending aorta in foetal life. This artery later regresses as the ligamentum arteriosum.Descending thoracic aorta
The descending thoracic aorta is a part of the aorta located in the thorax. It is a continuation of the descending aorta and contained in the posterior mediastinal cavity. The descending thoracic aorta begins at the lower border of the fourth thoracic vertebra where it is continuous with the aortic arch, and ends in front of the lower border of the twelfth thoracic vertebra, at the aortic hiatus in the diaphragm where it becomes the abdominal aorta.
At its commencement, it is situated on the left of the vertebral column; it approaches the median line as it descends; and, at its termination, lies directly in front of the column.
The descending thoracic aorta has a curved shape that faces forward, and has small branches. It has a radius of approximately 1.16 cm.Familial aortic dissection
Familial aortic dissection or FAD refers to the splitting of the wall of the aorta in either the arch, ascending or descending portions. FAD is thought to be passed down as an autosomal dominant disease and once inherited will result in dissection of the aorta, and dissecting aneurysm of the aorta, or rarely aortic or arterial dilation at a young age. Dissection refers to the actual tearing open of the aorta. However, the exact gene(s) involved has not yet been identified. It can occur in the absence of clinical features of Marfan syndrome and of systemic hypertension. Over time this weakness, along with systolic pressure, results in a tear in the aortic intima layer thus allowing blood to enter between the layers of tissue and cause further tearing. Eventually complete rupture of the aorta occurs and the pleural cavity fills with blood. Warning signs include chest pain, ischemia, and hemorrhaging in the chest cavity. This condition, unless found and treated early, usually results in death. Immediate surgery is the best treatment in most cases. FAD is not to be confused with PAU (penetrating atherosclerotic ulcers) and IMH (intramural hematoma), both of which present in ways similar to that of familial aortic dissection.Heart valve
A heart valve normally allows blood to flow in only one direction through the heart. The four valves are commonly represented in a mammalian heart that determines the pathway of blood flow through the heart. A heart valve opens or closes incumbent on differential blood pressure on each side.The four valves in the mammalian heart are:
The two atrioventricular (AV) valves, the mitral valve (bicuspid valve), and the tricuspid valve, which are between the upper chambers (atria) and the lower chambers (ventricles).
The two semilunar (SL) valves, the aortic valve and the pulmonary valve, which are in the arteries leaving the heart.The mitral valve and the aortic valve are in the left heart; the tricuspid valve and the pulmonary valve are in the right heart.
The heart also has a coronary sinus valve, and a inferior vena cava valve, not discussed here.Marfan syndrome
Marfan syndrome (MFS) is a genetic disorder of the connective tissue. The degree to which people are affected varies. People with Marfan tend to be tall and thin, with long arms, legs, fingers and toes. They also typically have flexible joints and scoliosis. The most serious complications involve the heart and aorta, with an increased risk of mitral valve prolapse and aortic aneurysm. Other commonly affected areas include the lungs, eyes, bones and the covering of the spinal cord.MFS is an autosomal dominant disorder. About 75% of the time, the condition is inherited from a parent, while 25% of the time it is a new mutation. It involves a mutation to the gene that makes fibrillin, which results in abnormal connective tissue. Diagnosis is often based on the Ghent criteria.There is no known cure for Marfan syndrome. Many people have a normal life expectancy with proper treatment. Management often includes the use of beta blockers such as propranolol or atenolol or, if that is not tolerated, calcium channel blockers or ACE inhibitors. Surgery may be required to repair the aorta or replace a heart valve. It is recommended that strenuous exercise be avoided.About 1 in 5,000 to 10,000 individuals have Marfan syndrome. It occurs equally in males and females. Rates are similar between races and in different regions of the world. It is named after Antoine Marfan, a French pediatrician who first described the condition in 1896.Thoracic aortic aneurysm
A thoracic aortic aneurysm is an aortic aneurysm that presents primarily in the thorax.
A thoracic aortic aneurysm is the "ballooning" of the upper aspect of the aorta, above the diaphragm. Untreated or unrecognized they can be fatal due to dissection or "popping" of the aneurysm leading to nearly instant death. Thoracic aneurysms are less common than an abdominal aortic aneurysm. However, a syphilitic aneurysm is more likely to be a thoracic aortic aneurysm than an abdominal aortic aneurysm. This condition is commonly treated via a specialised multidisciplinary approach with both Vascular Surgeons and Cardiac Surgeons.