What Are Aorta Clinical Significance

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 i.e. the common iliac arteries. It distributes oxygenated blood to all parts of the body through the systemic circulation. Having a vital role and function of the aorta, Siddha Spirituality of Swami Hardas Life System appeals to our valuable readers to read this article for well-being.

Aorta Meaning (??????? ?? ????)

The word ‘Aorta’ stems from the Late Latin aorta from Classical Greek aort? (?????), from aeir?, “I lift, raise” (?????). This term was first applied by Aristotle when describing the aorta and describes accurately how it seems to be ‘suspended’ above the heart.

Aorta Structure (??????? ?? ??????)

Sections (??????)

One way of classifying a part of the aorta is by anatomical compartment, where the thoracic, or thoracic portion, runs from the heart to the diaphragm, which then continues downward as the abdominal, 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, it starts as the ascending then travels superiorly from the heart and then makes a hairpin turn known as the aortic arch. Following the aortic arch, it then travels inferiorly as the descending. The descending has two parts, which begins to descend in the thoracic cavity and consequently is known as the thoracic. After it passes through the diaphragm, it is known as the abdominal aorta, which ends by dividing into two major blood vessels, the common iliac arteries and a smaller midline vessel, the median sacral artery.

Ascending aorta (????? ???????)

The ascending 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 to start out posterior to the pulmonary trunk, but end by twisting to its right and anterior side. The transition from ascending to the aortic arch is at the pericardial reflection.

At the root of the ascending, the lumen has three small pockets between the cusps of the aortic valve and the wall, 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.

Aortic arch (??????? ???)

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 aortic arch ends and the descending begins at the level of the intervertebral disc between the fourth and fifth thoracic vertebrae.

Thoracic aorta (????-???????)

The thoracic descending 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.

Abdominal aorta (??? ???????)

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.

Abdominal aorta Risk factors (??? ??????? ?? ????? ????)

AAAs generally affect elderly white men. Smoking appears to be the risk factor most strongly associated with AAA. In addition to increasing age and male sex, other factors include increased height, weight, body mass index, and body surface area.

A familiar clustering has been noted in 15-25% of patients undergoing surgical repair of AAA. Female sex, African American race, and the presence of diabetes mellitus are negatively associated with AAA. 

Aorta Development (??????? ?????)

The aortic arches start as five pairs of symmetrical arteries connecting the heart with the dorsal aorta, and then undergo a significant remodeling 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.

A failure of the aorticopulmonary septum to divide the great vessels results in persistent truncus arteriosus.

Microanatomy (??????????????)

The aorta is an elastic artery, and as such is quite distensible. It 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 requires an extensive network of tiny blood vessels called vasa vasorum, which feed the tunica externa and tunica media outer layers. 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 consists of concentric musculoelastic layers in mammals. 

Variation (???????)

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 is flipped.

Variations in the branching of individual arteries may also occur. For example, the left vertebral artery may arise from the aorta, instead of the left common carotid artery.

In patent ductus arteriosus, a congenital disorder, the fetal ductus arteriosis fails to close, leaving an open vessel connecting the pulmonary artery to the proximal descending aorta.

Aorta Function (??????? ?? ?????)

The aorta supplies all of the systemic circulations, 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.

Blood flow and velocity (???? ?????? ?? ???)

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. 

Aorta Diseases (??????? ?? ???)

Aorta Clinical significance (??????? ?? ??????? ?????)

• Aortic aneurysm – mycotic, bacterial e.g. syphilis, senile, genetic, associated with valvular heart disease
• Aortic coarctation – pre-ductal, post-ductal
• Dissection, and stenosis
• Aortitis, inflammation of the aorta that can be seen in trauma, infections, and autoimmune disease
• Atherosclerosis
• Ehlers–Danlos syndrome
• Marfan syndrome
• Trauma, such as traumatic aortic rupture
• Transposition of the great vessels

Other animals (????? ?????)

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. A second, dorsal aorta carries oxygenated blood from the gills to the rest of the body and is homologous with the descending of tetrapods. Amphibians also retain the fifth connecting vessel, so that it has two parallel arches.

 

Reference:

• https://en.wikipedia.org/wiki/Aorta
• https://www.medscape.com/answers/1979501-30916/what-are-the-risk-factors-for-abdominal-aortic-aneurysm-aaa
• https://en.wikipedia.org/wiki/Category:Diseases_of_the_aorta