Aorta

The aorta is the body's largest artery. The aorta starts at the top of the heart's muscular pumping chamber, the left ventricle. The valve in the aorta allows blood from the left ventricle to flow into the aorta. The aortic valve has three leaflets that open and close with each heartbeat to allow one-way blood flow. Through systemic circulation, the systemic aorta distributes oxygenated blood to all areas of the body.

The aorta is a tube with a diameter of just over an inch and a length of about a foot. There are four parts of the aorta.

• The ascending aorta is a 2-inch long artery that grows from the heart. The ascending aorta branches into coronary arteries, which supply blood to the heart.

• The aortic arch curves over the heart, branching out to supply blood to the head, neck, and arms.

• The descending thoracic aorta runs through the centre of the chest. The ribs and other chest structures receive blood from their tiny branches.

• The abdominal aorta starts at the diaphragm and splits into two iliac arteries in the lower abdomen. Branches of the abdominal aorta provide blood to most of the main organs.

Aorta Anatomy

The aorta is normally divided into sections in anatomical sources. The thoracic aorta, which runs from the heart to the diaphragm, is one way of classifying a section of the aorta by anatomical compartment. From the diaphragm to the aortic bifurcation, the aorta proceeds inward as the abdominal aorta.

Another system separates the aorta according to its path and blood flow direction. The aorta in this system begins as the ascending aorta, travels superiorly from the heart, and then makes the aortic arch, a hairpin turn. The aorta then travels inferiorly to the descending aorta after passing through the aortic arch. 

The descending aorta is divided into two parts. Since the aorta starts to descend in the thoracic cavity, it is called the thoracic aorta. The abdominal aorta is formed as the aorta passes through the diaphragm. The aorta splits into two main blood vessels, the common iliac arteries and the median sacral artery, and a smaller midline vessel, the femoral artery.

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There are four sections of the aorta which are explained as follows:

• Ascending aorta

• Aortic arch

• Descending thoracic aorta or thoracic aorta 

• Abdominal aorta

Ascending Aorta

• The ascending aorta starts in the left ventricle of the heart, where the aortic valve opens.

• It connects to the pulmonary trunk through a typical pericardial sheath.

• The aorta begins posterior to the pulmonary trunk and twists to the right and anterior side as these two blood vessels twist around each other.

• The pericardial reflection on the aorta is where the ascending aorta meets the aortic arch.

• The aortic sinuses, also known as the sinuses of Valsalva, are three narrow pockets between the cusps of the aortic valve and the aorta's wall at the root of the ascending aorta.

• The two coronary arteries that supply the heart are the only branches of the ascending aorta. They originate at the beginning of the aorta from the aortic sinuses on the opposite side of the aortic valve.

• The left coronary artery originates in the left aortic sinus, and the right coronary artery originates in the right aortic sinus. These two arteries supply the heart together.

• A coronary artery should not arise from the posterior aortic sinus. The left, right, and posterior aortic sinuses are referred to as left-coronary, right-coronary, and non-coronary sinuses, respectively.

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Aortic Arch

• The aortic arch starts at the level of the second sternocostal joint and is a continuation of the ascending aorta. Before going inferiorly, it arches superiorly, posteriorly, and to the left.

• At the stage of the T4 vertebra, the aortic arch comes to an end. The ligamentum arteriosum, a remnant of the foetal ductus arteriosus, also connects the arch to the pulmonary aorta.

• From the proximal to the distal the aortic arch is divided into three main divisions. 

• The first and largest branch of the brachiocephalic trunk ascends laterally to break into the right common carotid and right subclavian arteries. The right side of the head and spine, as well as the right upper limb, are supplied by these arteries.

• The left common carotid artery is responsible for supplying blood to the left side of the head and neck.

• The left upper limb is supplied by the left subclavian artery.

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Descending Thoracic Aorta or Thoracic Aorta

From T4 to T12, the descending thoracic aorta is located. It descends from the aortic arch, starting to the left of the vertebral column but eventually reaching the midline. The abdominal aorta emerges from the thorax from the aortic hiatus in the diaphragm.

The Following Are the Divisions of the Descending Thoracic Aorta:

• Bronchial arteries are lateral visceral branches that supply bronchial and peribronchial tissue as well as the visceral pleura. However, only the paired left bronchial artery normally branches off directly from the aorta, while the right usually branches off from the third posterior intercostal artery.

• The lymph glands and loose areolar tissue in the posterior mediastinum are supplied by mediastinal arteries, which are small arteries.

• The oesophageal arteries are unpaired visceral branches that emerge anteriorly to supply the oesophagus with blood.

• Small unpaired arteries that emerge anteriorly to supply the dorsal portion of the pericardium are known as pericardial arteries.

• The superior phrenic arteries are paired parietal branches that supply the diaphragm's upper part.

• Tiny paired arteries that branch out along the length of the posterior thoracic aorta are known as intercostal and subcostal arteries. With the exception of the first and second intercostal spaces, which are supplied by a branch from the subclavian artery, the intercostal spaces are supplied by nine pairs of intercostal arteries. The flat abdominal wall muscles are supplied by the subcostal arteries.

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Abdominal Aorta

Beginning at the level of the T12 vertebrae, the abdominal aorta continues the thoracic aorta. It measures around 13cm in length and terminates at the level of the L4 vertebra. The aorta bifurcates at this stage, forming the right and left common iliac arteries, which supply the lower body.

The following are the divisions of the abdominal aorta and their functions:

• The inferior phrenic arteries are a pair of parietal arteries that emerge from the back of the head at the level of T12. The diaphragm is supplied by them.

• The coeliac artery is a broad, unpaired visceral artery that arises anteriorly at T12. The liver, lung, abdominal oesophagus, spleen, superior duodenum, and superior pancreas are all supplied by the celiac trunk.

• The superior mesenteric artery is a broad, unpaired visceral artery that arises just below the celiac artery and runs anteriorly. The distal duodenum, jejuno-ileum, ascending colon, and a portion of the transverse colon are all supplied by it. It appears at L1's lower stage.

• The small paired visceral arteries that emerge either side posteriorly at the level of L1 to supply the adrenal glands are known as the middle suprarenal arteries.

• Renal arteries are a pair of visceral arteries that emerge laterally between the L1 and L2 vertebrae. They are responsible for supplying the kidneys.

• The gonadal arteries are a pair of visceral arteries that emerge from the stage of L2 laterally. The male gonadal artery is known as the testicular artery, while the female gonadal artery is known as the ovarian artery.

• The inferior mesenteric artery is a broad, unpaired visceral artery that emerges anteriorly at the level of L3 and runs through the abdomen. From the splenic flexure to the upper portion of the rectum, it supplies the large intestine.

• The coccyx, lumbar vertebrae, and sacrum are supplied by the median sacral artery, which emerges posteriorly at the level of L4 and supplies the coccyx, lumbar vertebrae, and sacrum.

• The abdominal wall and spinal cord are supplied by four pairs of parietal lumbar arteries that occur posterolaterally between the stages of L1 and L4.

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Conditions of Aorta

• Aortic atherosclerosis occurs when cholesterol plaques form in the aorta's wall, increasing the risk of stroke. Frequently, high blood pressure and abnormal cholesterol levels are to blame.

• An aortic aneurysm is a weakness in the infrarenal aorta's wall that causes a portion to swell outward. While aortic aneurysms develop slowly, they can be fatal if they rupture.

• High blood pressure causes the layers of the aorta's wall to break, resulting in aortic dissection. Aortic dissection is a potentially fatal condition.

• An interrupted aortic arch (IAA) is a rare heart condition in which the aorta fails to fully develop. The aorta is the heart's largest blood vessel, transporting oxygen-rich blood to the rest of the body. It's usually formed like an arch or curve. A part of the aorta is absent in an interrupted aortic arch, creating a void.

• When the aortic valve does not close fully, blood flows back into the heart with each beat, causing aortic insufficiency. Aortic insufficiency may be caused by autoimmune disorders, Marfan's syndrome, or endocarditis.

• Aortic insufficiency is also known as aortic regurgitation. Blood regurgitates into the left ventricle of the heart due to an incompletely closed aortic valve.

• Aortic stenosis occurs when the aortic valve narrows, causing the heart to work harder to pump blood through it. Aortic stenosis, which may cause chest pain and shortness of breath, is most often caused by rheumatic fever.

• The aorta narrows between its branches to the arms and those to the legs, causing coarctation. Owing to elevated blood pressure in the upper body, this birth defect causes heart strain.

• Aortitis is a condition in which the aorta becomes inflamed. Aortitis is commonly caused by infections or autoimmune diseases.

• Humans and animals with tortuous aortas and veins are normal. Although mild tortuosity is asymptomatic, extreme tortuosity may result in distal organ ischemia. Atherosclerosis, hypertension, genetic abnormalities, and diabetes mellitus have all been related to tortuous arteries and veins in clinical studies.

Dissection of Aorta

The inner layer of the aorta, the massive blood vessel branching off the heart, tears in an aortic dissection, which is a severe disorder. The inner and middle layers of the aorta dissect as blood rushes through the tear. Dissection of the aorta is often fatal when the blood-filled channel ruptures through the outside aortic wall. Aortic dissection is a rare occurrence. Men in their 60s and 70s are the most commonly affected. When an aortic dissection is diagnosed early and treated immediately, however, the chances of survival increase dramatically.

Symptoms of Dissection of Aorta

• Sudden extreme chest or upper back pain that radiates to the neck or down the back, sometimes characterised as tearing, ripping, or shearing

• Abdominal pain that comes on suddenly.

• Consciousness loss

• Breathing problems

• Similar to the symptoms of a stroke, you can experience sudden trouble communicating, loss of vision, weakness or paralysis on one side of the body.

• Leg pain with a weak pulse in one arm or thigh relative to the other

• Leg paralysis causes difficulty walking.

Causes of Dissection of Aorta

An aortic dissection occurs when a section of the aortic wall becomes compromised. The aortic tissue can be stressed by chronic high blood pressure, making it more vulnerable to tearing. You may also be born with a disorder that causes a weakened and swollen aorta, such as Marfan syndrome, bicuspid aortic valve, or other less common disorders that cause blood vessel walls to weaken. Aortic dissections are caused by serious injuries to the chest region, such as those sustained in car accidents, on a rare occasion.

Depending on the part of the aorta is affected, aortic dissections are divided into two groups:

• Type A: A tear in the section of the aorta where it leaves the heart or a tear in the upper aorta (ascending aorta), which may stretch into the abdomen, is the most common and dangerous kind.

• Type B: A tear in the lower aorta (descending aorta) causes Type B, which may spread into the abdomen.

Complications of Dissection of Aorta

• Death from extreme internal bleeding may result from an aortic dissection.

• Kidney failure or life-threatening intestinal injury are examples of organ damage.

• Stroke.

• Harm to the aortic valve (aortic regurgitation) or a rupture into the heart's lining (cardiac tamponade).

Medical Tests on Aorta

• An aortogram, also known as an angiogram, is a procedure in which a catheter is inserted into a groyne artery and progressed into the aorta. X-rays may create an image of the aorta on a screen thanks to contrast material injected into the body.

• Abdominal ultrasound is a test that uses sound waves to create a picture of the abdomen. Aortic aneurysms in the abdomen may be diagnosed and assessed to determine the likelihood of rupture.

• CT scan is a procedure in which a CT scanner creates images of the aorta and associated structures using X-rays and a monitor.

• A magnetic resonance imaging (MRI) scan is a procedure in which radio waves are used to create images of the aorta within a magnetic field.

• A transthoracic echocardiogram is a procedure in which an ultrasound probe is mounted on the chest and ultrasound waves are projected onto the aorta and heart. During transthoracic echocardiograms, the sternum (breastbone) blocks direct ultrasound views of the aorta.

• An ultrasound probe on the end of a flexible tube is advanced through the mouth and down the oesophagus in a transesophageal echocardiogram. Transesophageal echocardiograms provide a clearer view of the aorta's first section.

Treatments of Aorta

• When aortic aneurysms exceed a certain size, surgery may be required to prevent them from rupturing. This is usually done through an abdominal incision.

• Aorta grafting, also known as endograft, is a procedure that involves surgically replacing or reinforcing a damaged section of the aorta with synthetic mesh.

• Aortic valve replacement is a surgical procedure that replaces a weakened aortic valve to treat aortic stenosis. The new aortic valve may be man-made or pig-derived.

• When an aortic aneurysm, dissection, or coarctation occurs, a portion of the aorta can need to be surgically removed. The cut edges are either directly connected or connected with a graft by a surgeon.

Conclusion

The aorta is the major and the largest artery that connects your heart to the rest of the body. The aortic valve is where blood exits the heart. The blood then passes through the aorta, where it forms a cane-shaped curve that enables other major arteries to provide oxygen-rich blood to the brain, muscles, and other cells. When the aorta has a problem, it puts the heart and the whole body's blood supply at risk.