The aorta is the largest vessel in the body both in length and diameter, and in the volume of blood flow, therefore, proper blood supply to all organs and systems of the body depends on it. The pathology of this largest artery in the human body negatively affects the work of all organs, the vessels of which branch below the level of damage.
Aortic anatomy
Conventionally, this large vessel is divided into three parts, based on its direction:
- Upstream department.
- The aortic arch, the anatomy of which is considered separately.
- The descending part. This department is the longest. It ends when approaching the fourth lumbar vertebra. Here the common iliac arteries begin , into which the abdominal aorta is divided.
Anatomy and Topography
The ascending aorta extends from the left ventricle. Having reached the second rib, it passes into the so-called arc, which, curving to the left, at the level of the fourth vertebra of the thoracic spine, goes into the descending part.
The anatomy of the aorta and the location of its departments and main branches relative to other internal organs at various levels is of great importance in studying the structure of the chest and abdominal cavities.
Thoracic department
Starting at the level of the fourth thoracic vertebra, the thoracic segment of the aorta is directed almost vertically downward, located in the posterior mediastinum. To the right of the aorta, the thoracic duct and unpaired vein lie in this place; left - parietal pleura.
Abdominal
This section begins when the aortic vessel passes through the corresponding hole in the diaphragm and extends to the level of the fourth lumbar vertebra. In the abdominal cavity, aortic anatomy has its own peculiarity: it lies in the retroperitoneal cellular space, on top of the vertebral bodies of the lumbar region, surrounded by the following organs:
- to the right of it lies the inferior vena cava;
- on the front side, the posterior surface of the pancreas, the horizontal segment of the duodenum, and also part of the root of the mesentery of the small intestine are adjacent to the abdominal aorta.
Having reached the level of the fourth vertebra of the lumbar, the abdominal aorta is divided into two iliac arteries. They provide blood supply to the lower extremities (this place is called bifurcation, aortic bifurcation, and is its end).
In accordance with the location of the parts of this large vessel, the anatomy of the aorta and its branches is examined by departments.
Branches of the ascending department
This is the initial section of the vessel. Its duration is short: from the left ventricle of the heart to the cartilage of the second rib on the right.
At the very beginning of the ascending aorta, the right and left coronary arteries branch from it , the heart supplying area of which is the heart.
Aortic arch branches
The anatomy of the arc has the following feature: large arteries originating from the convex part of it, carrying blood supply to the skull and upper limbs. The concave part gives a small size of the branch, not having a permanent location.
The following branches extend from the convex side of the aortic arch (from right to left):
- brachiocephalic trunk ("brachiocephalic");
- left common carotid artery;
- left subclavicular artery.
The concave part of the arc gives off thin arterial vessels suitable for the trachea and bronchi. Their number and location may be different.
Descending Branch
The descending aorta, in turn, is divided into departments:
- Thoracic, located above the diaphragm;
- Abdominal, located below the diaphragm.
Thoracic department:
- Parietal arterial vessels for blood supply to the walls of the chest: upper diaphragmatic arteries, branching surfaces of the diaphragm from the side of the chest cavity, and posterior intercostal arterial vessels supplying blood to the intercostal and rectus abdominal muscles, mammary gland, spinal cord, and also soft tissues of the back.
- Visceral vessels extending from the thoracic branch, branch in the organs of the posterior mediastinum.
Abdominal:
- Parietal branches branching in the walls of the abdominal cavity (four pairs of lumbar arteries supplying the muscles and skin of the lumbar region, abdominal walls, lumbar spine and spinal cord) and the lower surface of the diaphragm.
- Visceral arterial branches going to the abdominal organs are paired (to the adrenal glands, kidneys, ovaries and testicles; moreover, the names of the arteries correspond to the names of the organs supplied to them by the blood) and unpaired. The names of the visceral arteries correspond to the names of the organs supplied to them by blood.
Vessel wall structure
The term “aortic anatomy” also includes the wall structure of this largest arterial vessel in the body. The structure of its wall has certain differences from the wall structure of all other arteries.
The structure of the aortic wall is as follows:
- The inner shell (intima). It is a basement membrane lined with endothelium. The endothelium actively responds to signals received from the blood circulating in the vessel, transforms them and transfers them to the smooth muscle layer of the vascular wall.
- The middle shell. This layer consists of circularly located elastic fibers in the aorta (unlike other arterial vessels in the body, where collagen, smooth muscle, and elastic fibers are present - without any of them being clearly dominant). The aortic anatomy has a feature: the middle membrane of the aortic wall is formed mainly by elastic fibers. The function of the middle shell is to maintain the shape of the vessel, and also provides its motility. The middle layer of the vascular wall is surrounded by interstitial substance (fluid), the bulk of which penetrates here from the blood plasma.
- Adventitia (outer shell of the vessel). This connective tissue layer contains mainly collagen fibers and perivascular fibroblasts. It is penetrated by blood capillaries and contains a large number of vegetative nerve fiber endings. The perivascular connective tissue layer is also a conductor of signals directed to the vessel, as well as the pulses emanating from it.
Functionally, all layers of the vascular wall are interconnected and are capable of transmitting an information impulse to each other - both from intima to the middle layer and adventitia, and in the opposite direction.