Location, function and size of the aorta

What is the aorta and where is it located?

The aorta is considered the largest vessel in the body and plays a key role in maintaining normal hemodynamics. It is with her that a large circle of blood circulation begins, which supplies oxygen-rich blood to all structures of the body. It departs from the left ventricle of the heart, for the most part is located along the spinal column and ends, diverging into two branches: the right and left iliac.

Structure and departments

Belongs to the elastic type of arteries, histologically, its wall is formed by three layers:

1. Internal (intima) - represented by the endothelium. It is he who is most susceptible to pathological processes, including atherosclerosis. This membrane forms the aortic valve.
2. Medium (media) - mainly consists of elastic fibers, which, stretching, increase the lumen of the channel. This allows you to maintain a stable blood pressure. It also contains small amounts of smooth muscle fibers.
3. External (adventitia) - consists mainly of connective tissue elements with a low content of elastic fibers and a high content of collagen, which gives the vessel additional rigidity, despite the small wall thickness.

Topographically, the artery consists of three main parts: the ascending section, the arch and the descending.

The ascending section begins in the region of the third intercostal space, along the left edge of the sternum. At the point where the vessel leaves the heart are the aortic valves. Their second name is "lunar" because they resemble curved pockets, consisting of three valves and preventing backflow of blood after the aorta has exited the ventricle. There are also small bulges - sinuses, in which the coronary arteries that feed the myocardium begin. In the same place, there is a short extended section - an onion. Opposite the articulation of the second right rib with the sternum, the ascending aorta passes into an arch.

The arc turns to the left and ends near the fourth thoracic vertebra, forming the so-called isthmus - the place where the artery is somewhat narrowed. Behind it is the tracheal bifurcation (the point at which the breathing tube divides into two bronchi). Branches that feed the upper body extend from its upper side:

• brachiocephalic trunk;
• left general sleepy;
• left subclavian.

The descending section is the longest part of the vessel, consisting of the thoracic (thoracic) and abdominal (or abdominal) sections. It originates from the isthmus of the arch, for the most part is located in front of the spine and ends near the fourth lumbar vertebra. At this point, the aorta diverges into the right and left iliac branches.

The thoracic region is located in the thoracic cavity and goes to the aortic opening of the respiratory muscle of the diaphragm (opposite the 12th vertebra). All along, branches depart from it, blood supplying organs of the mediastinum, lungs, pleura, muscles and ribs.

The final, abdominal part, provides blood supply to the abdominal and pelvic organs, the abdominal wall, as well as the lower extremities.

Normal values ​​for vessel size

Determining the diameter of the aorta is very important in the diagnosis of many of its pathologies, especially aneurysms or atherosclerosis. This is usually done using x-rays (such as computed tomography or magnetic resonance imaging) or ultrasound (echocardiography) examinations. It is important to remember that this value is very variable, since it changes depending on age and gender.

Blood flow, velocity and pressure

Also, to study the work of the aorta, its functional indicators are examined. This is usually done with ultrasound or Doppler ultrasound.

The systolic pressure in the vessel is about 120-140 mm Hg. Art., diastolic - 70-90 mm Hg. Art. The value may differ slightly depending on age and individual characteristics.

The linear blood flow velocity in the initial sections is about 0.7-1.3 m / s. More distally (i.e., farther from the beginning) it decreases to 0.5 m / s.

The volumetric velocity is normally 4-5 liters per minute.

How are changes in the work of the aorta reflected in the systemic blood flow?

The aorta is the only vessel from which the systemic circulation begins. Any of her diseases cause severe hemodynamic disturbances, up to cardiovascular failure.

First of all, pressure suffers. As a result of sclerosis and calcification, the arterial wall becomes rigid and loses its elasticity, and this is one of the causes of hypertension. When an aneurysm ruptures, the opposite is true - blood pressure drops sharply.

Defects of the aortic valves are very dangerous. Failure leads to regurgitation, that is, the return of blood to the ventricle, due to which it is overstretched, which leads to cardiomyopathy. Cardiac output is also reduced as a result of stenosis. However, this is due to the fact that the flaps do not open completely. At the same time, blood flow in the coronary arteries is disturbed. This leads to the development of angina pectoris.

The degree of blood flow disturbance largely depends on the localization of the pathological process: the closer it is to the beginning of the vessel, the more systemic its effect will be, while damage to only the abdominal region causes hypoxia of a limited area of ​​the body (lower body).

Major diseases and developmental anomalies

All diseases of the aorta, depending on the origin, are divided into two large classes: congenital and acquired.

The first include genetically determined developmental defects:

1. Insufficiency of the valves - due to the underdevelopment of the valves, they do not completely close, and therefore, in diastole, part of the blood returns to the ventricle. As a result, myocardial hypertrophy develops and the initial section of the aorta expands.
2. Valve stenosis - characterized by fusion of the leaflets, which makes it difficult for blood to pass through the narrow opening, which causes a decrease in systolic output and the development of dilated cardiomyopathy.
3. Coarctation is a narrowing of the thoracic aorta. The altered segment can be from two millimeters to several centimeters long, as a result of which the pressure increases significantly in the area above the narrow part, but drops significantly in the lower parts.
4. Marfan's syndrome is a genetically determined disease characterized by damage to the connective tissue. Differs in the frequent appearance of aneurysms and valvular defects.
5. Double aortic arch is a defect in which the vessel is divided into two parts. Each of them bends around the esophagus and trachea, as a result of which they are enclosed in a ring. Hemodynamics are usually not impaired, the clinic is characterized by difficulty in swallowing and breathing.
6. Right-sided aortic arch - with this anomaly, the artery does not go to the left, as it should be normal, but to the right. Usually, the course of the disease is asymptomatic, except when the aortic ligament forms a ring around the trachea and esophagus, thereby squeezing them.

Acquired diseases include:

1. Aneurysm is a more than double expansion of a portion of a vessel, which occurs due to the pathology of the walls.This leads to serious hemodynamic disturbances, primarily to hypoxia of certain organs. The specific symptomatology is due to the localization of the lesion.
2. A dissecting aneurysm is characterized by a rupture of the sclerosed inner membrane, due to which blood flows into the cavity formed between the walls and causes their further stratification. Over time (usually after several days), a complete destruction of the defect occurs, which causes massive internal bleeding and instant death.
3. Atherosclerosis - characterized by the deposition of lipoprotein complexes in the inner layer, which leads to the formation of plaques, calcification and narrowing of the lumen. As a result, there is oxygen starvation (hypoxia) of organs and tissues, as well as thrombotic complications (including strokes).
4. Nonspecific aortoarteritis (Takayasu syndrome) is an autoimmune vasculitis in which proliferative inflammation develops in the vessel wall, leading to induration, obstruction, or aneurysm formation.

What methods of treatment and correction exist and are considered effective?

A feature of the pathologies of the aorta is that in their treatment, invasive surgical intervention is mainly used. Conservative therapy is used only to support vital signs and relieve symptoms so that surgery can be performed safely.

There is now a trend towards minimally invasive endoscopic surgeries that are safer and more effective.

Today, the following surgical methods of treatment are used:

• resection with anastomosis - used for small aneurysms or coarctations;
• prosthetics;
• coronary artery bypass grafting (creation of bypass pathways of blood circulation) - for occlusive diseases, coronary artery disease or heart attack;
• implantation of artificial valves, balloon valvuloplasty,

Conclusions

Due to the peculiarities of anatomy and physiology, the aorta is the leading vessel of the human body. It provides blood supply to all tissues, and therefore any of its pathologies lead to extensive disturbances in the activity of the whole organism. In recent years, the mortality rate from vascular pathologies has been decreasing due to the introduction of new minimally invasive surgical techniques.