Aorta

What is Aorta?

The oxygen rich blood is pumped by the heart every time when it contracts and it needs to be delivered to every single organ and cell of the human body. It is the aorta that carries this enriched blood out from the heart and distributes it, through a pipeline resembling system, by dividing itself in smaller and thinner tubes known as arteries and capillaries. The aorta is the main and largest artery of the human body. Its length and structure are important, for the appropriate flow and pressure of blood within, to ensure an adequate delivery of blood to every section of the human body.

Location of Aorta

Location of aorta in the human heart

The main artery of the body begins at the heart and ends when it divides itself in the iliac arteries to supply blood to the lower limbs. The aorta is found in the trunk of the human body and it is divided and named according to its location in thoracic aorta and abdominal aorta. The diaphragm is the point of reference between these two regions of the aorta.

Aorta Structure

The aorta is a complex structure formed by the combination of different tissues and components such as nerves, extracellular matrix, endothelial cells, intimal cells and smooth muscle.

The walls of this “pipeline” are formed, from inside-out by:

  • Tunica intima or simply “intima” which is made of one layer of epithelial cells and is in contact with the blood. It provides a soft surface for the blood’s flow through the aorta.
  • Tunica media is, as its name refers, the middle layer of the aorta. The media, for short, is made of between five to seven layers of smooth muscle, surrounding the lumen of the aorta, and elastic tissue. This particular composition of the media layer provides the aorta with flexibility which is needed for its contraction or expansion with every heartbeat. This tissue layer also helps the appropriate distribution of the blood.
  • Tunica externa or adventitia is the outer layer of the aorta. The adventitia is formed mainly of collagen. The collagen is important to keep the vessel attached or anchored to the surrounding tissues and organs.

There is a regional division of the aorta according to the direction of the blood flow through the vessel.

Structure of Aorta

The ascending aorta is the first of the four regions. In the ascending aorta the blood has a high pressure as it exits from the left ventricle due to its strong contraction. The beginning of this region is marked by the aortic valve of the heart and just beneath it the aorta has three small orifices known as aortic sinuses. These sinuses supply the coronary arteries (arteries of the heart) with blood.

The following region is the aortic arch. Its importance is in regulating the pressure and the pH of the blood as it goes out from the heart’s left ventricle due to the presence of chemoreceptors and baroreceptors. This first portion of the aorta sends the information to the brain to do the most convenient adjustments to ensure the balance and equilibrium of the blood delivery. The aortic arch has three important branches that supply the upper part of the body and brain with blood, this branches are:

  • Subclavian artery
  • Left common carotid artery
  • Brachiocephalic trunk

Aorta diagram – showing different regions

The third region is known as the descending thoracic aorta. As its name refers, this region is located in the thorax and supplies the blood to the organs and other structures of this cavity. The descending thoracic aorta branches are:

  • Intercostal arteries
  • Subcostal arteries
  • Left bronchial arteries
  • Branch to the esophagus
  • Branch to the mediastinum
  • Branch to the pericardium
  • Superior phrenic arteries

As the descending aorta passes through the diaphragm its name changes to abdominal aorta where it creates the branches to supply the organs and structures of the abdomen with blood. The abdominal aorta branches are:

  • Lumbar arteries
  • Musculophrenic arteries
  • Renal arteries
  • Suprarenal arteries
  • Median sacral arteries
  • Visceral arteries (Superior and inferior mesenteric arteries, celiac trunk)
  • Gonadal arteries (Ovarian arteries in women, Testicular arteries in men)

Function of Aorta

The main role of this vital structure in the human body is to supply blood to the entire economy of the body with the exception of the lungs. The structure of the aorta is indispensable to complete this function. The pumping of the blood from the heart with each contraction creates a pulsatile flow that needs to be kept in order to ensure an appropriate supply of the blood to the body. The elasticity, flexibility and receptors of the aorta make this function possible.

Clinical significance

There are different types of pathologies that can affect the aorta but we can also find some abnormalities occurring with the aorta as it is the case with the narrowing of the lumen (interior) of the aorta. This condition is known as “coarctation of the aorta”. The coarctation of the aorta is a congenital condition and it is commonly found in the aortic arch. The condition causes the left ventricle to expel the blood stronger in order for it to be able to get to the lower regions of the body. This can lead to an enlargement of the ventricle and posterior failure of the heart function.

The opposite situation, where the lumen is enlarged, is scientifically known as “aneurysm of the aorta”. The aneurysms are formed due to the effect of the blood pressure in the walls of the aorta creating a protrusion that, with the time, can progress in its severity. This condition may cause internal bleeding due to the rupture of the walls of the aorta. The aneurysm of the aorta can be present in any region of the aorta but it is most commonly found in the abdominal region.

Because the aorta is such a large and important artery a rupture in any of its regions is a life-threatening condition. There are some risk factors related with the aneurysms of the aorta such as: the age (it is common to find this condition in patients of 65 years old or more), gender (the condition being more common in men than in women), lifestyle habits (particularly common in smokers), pathological conditions (for example, high blood pressure) and the presence of cases of aneurysms in the family history. For prevention reasons it is vital to perform periodicals checkups aimed at the early discovery of the aneurysms.

The diagnosing of the aortic aneurysms is made with the help of ultrasound and MRI. The treatment depends on the severity of the aneurysm and it can be done with a minimally invasive surgery or an open-heart surgery. During the recovery process from both procedures it is necessary to change and improve existing risks factors. A better diet, physical activity, medications and blood pressure control are vital for achieving a full recovery.

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