The ascending aorta (AAo) is a portion 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 ...

commencing at the upper part of the base of 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 upper ...

, on a level with the lower border of the third costal cartilage behind the left half of 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. Sh ...

Structure

It passes obliquely upward, forward, and to the right, in the direction of the heart's axis, as high as the upper border of the second right

costal cartilage The costal cartilages are bars of hyaline cartilage that serve to prolong the ribs forward and contribute to the elasticity of the walls of the thorax. Costal cartilage is only found at the anterior ends of the ribs, providing medial extension. ...

, describing a slight curve in its course, and being situated, about behind the posterior surface of the

. The total length is about .

Components

The aortic root is the portion of the aorta beginning at the aortic annulus and extending to the sinotubular junction. It is sometimes regarded as a part of the ascending aorta, and sometimes regarded as a separate entity from the rest of the ascending aorta. Between each commissure of the

aortic valve The aortic valve is a valve in the heart of humans and most other animals, located between the left ventricle and the aorta. It is one of the four valves of the heart and one of the two semilunar valves, the other being the pulmonary valve. The ...

and opposite the cusps of the aortic valve, three small dilatations called the

aortic sinuses An aortic sinus, also known as a sinus of Valsalva, is one of the anatomic dilations of the ascending aorta, which occurs just above the aortic valve. These widenings are between the wall of the aorta and each of the three cusps of the aortic valv ...

. The sinotubular junction is the point in the ascending aorta where the aortic sinuses end and the aorta becomes a tubular structure.

Size

A thoracic aortic diameter greater than 3.5 cm is generally considered dilated, whereas a diameter greater than 4.5 cm is generally considered to be a

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 dissec ...

. Still, the average diameter in the population varies by for example age and sex. The upper limit of standard reference range of the ascending aorta may be up to 4.3 cm among large, elderly individuals.

Relations

At the union of the ascending aorta with the

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 a ...

the caliber of the vessel is increased, owing to a bulging of its right wall. This dilatation is termed the bulb of the

, and on transverse section presents a somewhat oval figure. The ascending aorta is contained within the

pericardium The pericardium, also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong connective tissue (fibrous pericardium), and an inner layer made of ...

, and is enclosed in a tube of the serous pericardium, common to it and the

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 t ...

. The ascending aorta is covered at its commencement by the trunk of the

and the right auricula, and, higher up, is separated from the sternum by the pericardium, the right pleura, the anterior margin of the right lung, some loose areolar tissue, and the remains of the thymus; posteriorly, it rests upon the left atrium and right pulmonary artery. On the right side, it is in relation with the

superior vena cava The superior vena cava (SVC) is the superior of the two venae cavae, the great venous trunks that return deoxygenated blood from the systemic circulation to the right atrium of the heart. It is a large-diameter (24 mm) short length vein th ...

and

right atrium The atrium ( la, ātrium, , entry hall) is one of two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular valves. There are two atr ...

, the former lying partly behind it; on the left side, with the pulmonary artery.

Branches

The only branches of the ascending aorta are the two

coronary arteries The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart muscle. The heart requires a continuous supply of oxygen to function and survive, much like any other tissue or organ of ...

which supply the heart; they arise near the commencement of the aorta from the aortic sinuses which are opposite the

Clinical significance

' is extensive

atherosclerotic Atherosclerosis is a pattern of the disease arteriosclerosis in which the wall of the artery develops abnormalities, called lesions. These lesions may lead to narrowing due to the buildup of atheromatous plaque. At onset there are usually no sy ...

calcification of the ascending aorta. It makes

aortic surgery Open aortic surgery (OAS), also known as open aortic repair (OAR), describes a technique whereby an abdominal, thoracic or retroperitoneal surgical incision is used to visualize and control the aorta for purposes of treatment, usually by the repla ...

difficult, especially

aortic cross-clamp An aortic cross-clamp is a surgical instrument used in cardiac surgery to clamp the aorta and separate the systemic circulation from the outflow of the heart. An aortic cross-clamping procedure serves, for example, in the repairing of coarctati ...

ing, and incisions may result in excessive aortic injury and/or

arterial embolism Arterial embolism is a sudden interruption of blood flow to an organ or body part due to an embolus adhering to the wall of an artery blocking the flow of blood, the major type of embolus being a blood clot (thromboembolism). Sometimes, pulmona ...

Images

Image:Gray490.png, Front view of heart and lungs. Image:Gray505.png, The arch of the aorta, and its branches. File:Thoracic cavity of foetus - great vessels.JPG, Fetal ascending aorta File:Slide7eeee.JPG, Ascending aorta File:Slide12eeee.JPG, Ascending aorta File:Slide8gggg.JPG, Ascending aorta File:Slide2wwww.JPG, Ascending aorta File:Slide5444.JPG, Ascending aorta File:Slide11444.JPG, Ascending aorta File:Ascending aorta.png, Ascending aorta

References

External links

{{Authority control Arteries of the thorax Aorta de:Aorta#Abschnitte