Generality
The abdominal aorta is the second of the two large sections, in which the aorta is divided, that is the main artery of the human body.
Next to the thoracic aorta - which is therefore the first large section of the aorta - the abdominal aorta traverses the abdomen in the direction of the lower limbs, starting its course at the level of the diaphragm and ending at the IV lumbar vertebra, where it bifurcates in the right common iliac artery and left common iliac artery.
During his journey along the abdomen, the abdominal aorta gives rise to numerous branches (branches of the abdominal aorta), which serve to distribute the oxygenated blood in the various tissues and organs of the abdomen and pelvis.
In the pathological field, the abdominal aorta is known, above all, for a condition called abdominal aortic aneurysm.
Short review of the Aorta
The aorta is the largest and most important artery in the human body.
With origin in the heart (to be precise from the left ventricle of the heart), this fundamental arterial vessel is provided, from the beginning, with branches (or branches), through which it supplies oxygenated blood to every district of the human body, from the head in the lower limbs, passing through the upper limbs and the trunk.
What is the Abdominal Aorta?
The abdominal aorta is the main artery of the abdominal cavity .
The last part of the aorta, the abdominal aorta is the continuation of the thoracic aorta, which is that section of the aorta that can be subdivided, starting from the heart, into: ascending aorta, aortic arch and descending aorta .
In light of the information just provided on the abdominal aorta and the thoracic aorta, a valid definition of abdominal aorta could also be: "the abdominal aorta is the aorta tract that follows the thoracic descending aorta and that concludes the path of the main artery of the human body ".
Anatomy
The abdominal aorta begins its course at the height of the XII thoracic vertebra (vertebra T12 ), more or less in correspondence of the diaphragm . From here, it runs along the entire abdomen, keeping slightly to the left of the spine, up to the IV lumbar vertebra ( L4 vertebra), where it separates into the two common iliac arteries (right common iliac artery and left common iliac artery).
During his journey, the abdominal aorta gives rise to numerous branches, which, in technical jargon, are called branches of the abdominal aorta .
Origin of the Abdominal Aorta: the details
To mark the beginning of the abdominal aorta is the passage of the aorta through the so-called aortic hiatus .
Also known as an aortic or aortic foramen, the aortic hiatus is the posterior opening to the diaphragm, resulting from the particular disposition of the latter with respect to the vertebral column.
The aortic hiatus resides in the posterior part of the diaphragm and is delimited by the median arcuate ligament, anteriorly, from the pillars (the so-called crus ) right and left of the diaphragm, laterally, and from the inferior margin of the body of the XII thoracic vertebra, posteriorly.
In addition to the abdominal aorta, the thoracic duct (structure of the lymphatic system) and the azygos vein pass through the aortic hiatus.
In crossing the aortic hiatus, the abdominal aorta passes, anteriorly, to the body of the T12 vertebra and, posteriorly, to the diaphragm.
Abdominal Aorta Path: the details
From where it begins, the abdominal aorta follows a path downwards (ie towards the lower limbs), which sees it reside in the posterior part of the abdomen, in front of and slightly to the left of the vertebral column, in an anatomical space called retroperitoneal space .
During this journey, it runs parallel to the inferior vena cava, which is located to its right.
As it approaches the end (that is the bifurcation in the two iliac arteries), the abdominal aorta tends to decrease slightly in diameter, passing from about 2 centimeters (in an average individual) to slightly less.
The end of the course of the abdominal aorta is clear; in fact, in the IV lumbar vertebra, the abdominal aorta is the protagonist of a real bifurcation.
The result of this bifurcation, the two common iliac arteries, are the arterial vessels destined to spread, through the different branches, to the lower limbs (obviously, the right iliac artery is oriented towards the right lower limb, while the iliac artery left is oriented towards the left lower limb).
Branches of the Abdominal Aorta
Distinct in parietal (that is, that they supply the muscles and tissues of the so-called abdominal wall, visceral (that is, which supply the abdomen and pelvis organs) and terminals (ie which mark the end of the abdominal aorta), the branches of the abdominal aorta are, starting from the origin:
- The two lower phrenic arteries (one on each side).
Origin: XII thoracic vertebra.
Type: parietal.
Orientation: rear.
- The celiac artery .
Origin: XII thoracic vertebra.
Type: visceral.
Orientation: front.
- The superior mesenteric artery .
Origin: The lumbar vertebra.
Type: visceral.
Orientation: front.
- The two average adrenal arteries (one on each side).
Origin: The lumbar vertebra.
Type: visceral.
Orientation: rear.
- The two renal arteries (one on each side).
Origin: between I and II lumbar vertebra.
Type: visceral.
Orientation: front.
- The two genital arteries (one on each side).
Origin: II lumbar vertebra.
Type: visceral.
Orientation: front.
Short note: in humans, the genital arteries are also called testicular arteries ; in women, however, they are also called ovarian arteries .
- The four lumbar arteries (two per side).
Origin: between the I lumbar vertebra and the IV lumbar vertebra.
Type: parietal.
Orientation: rear.
- The inferior mesenteric artery .
Origin: III lumbar vertebra.
Type: visceral.
Orientation: front.
- The medial sacral artery .
Origin: IV lumbar vertebra.
Type: parietal.
Orientation: rear.
- The two common iliac arteries (one on each side).
Origin: IV lumbar vertebra.
Type: terminal.
Orientation: rear.
It should be noted that among these branches there are further branched and unbranched branches.
The branches of the abdominal aorta further branched are: the celiac artery, the superior mesenteric artery, the inferior mesenteric artery and the two common iliac arteries.
Subdivisions of the Abdominal Aorta
According to the most classical anatomical descriptions of the abdominal aorta, the latter can be divided into two segments: the so-called paravisceral segment (or suprarenal abdominal segment ) and the so-called infrared segment .
The paravisceral segment is the abdominal aorta tract that goes from the diaphragm to the renal arteries, while the infrared segment is the abdominal aorta tract that extends from after the renal arteries to the branch in the two iliac arteries.
Relationships of the Abdominal Aorta
- At the point of origin (XII thoracic vertebra), the abdominal aorta is bordered by:
- The median arcuate ligament, anteriorly;
- The anterior longitudinal ligament and the underlying body of the XII thoracic vertebra, posteriorly;
- The vein azygos, the thoracic duct and the right pillar of the diaphragm (or right crus of the diaphragm), on the right side;
- The left pillar of the diaphragm (or left crus of the diaphragm), on the left side.
- Starting from after the point of origin, the abdominal aorta establishes relations of closeness with:
- The small omentum and the stomach, anteriorly but only up to where the two anatomical elements just mentioned extend;
- The splenic vein and the body of the pancreas, anteriorly but only in the section between the origin of the celiac artery and the origin of the superior mesenteric artery;
- The left renal vein, the uncinate process of the pancreas and the lower part of the duodenum, anteriorly but only in the section between the origin of the superior mesenteric artery and the origin of the inferior mesenteric artery;
- The anterior longitudinal ligament tract that covers the lumbar vertebrae, posteriorly;
- The inferior vena cava, on the right side. This association continues until the bifurcation of the abdominal aorta in the two common iliac arteries. Initially, for accuracy up to the navel, the abdominal aorta resides, with respect to the inferior vena cava, in a more backward position; from then the navel, instead, takes a more advanced position;
- The ascending duodenum and subsequent small intestine loops, on the left side.
Function
Thanks to its innumerable branches, the abdominal aorta covers the important function of supplying the tissues and organs of the abdomen, the tissues and organs of the pelvis and lower limbs with oxygenated blood.
The table below shows in a clear and immediate way to which anatomical districts the different branches of the abdominal aorta provide oxygenated blood.
diseases
In pathology, the abdominal aorta owes its notoriety, mainly, to a condition called as an abdominal aortic aneurysm and, secondly, to the injuries sustained to it due to trauma (eg: traffic accident) or penetrating wounds in the abdomen (eg, subsequent injuries to stabbings or shootings).
What is Abdominal Aortic Aneurysm?
Also known as an abdominal aneurysm or with the simple acronym AAA, the abdominal aortic aneurysm is a permanent abnormal dilatation, with a saccular or fusiform aspect, of a short segment of abdominal aorta.
In medicine, to be able to talk about abdominal aortic aneurysm it is necessary that the diameter of a tract of the latter measures more than 3 centimeters (NB: remember that, in normal conditions, the diameter of the abdominal aorta is 2 centimeters, except for slight variations).
Although it often lacks an associated symptomatology, the abdominal aortic aneurysm represents an important threat to the survival of its bearer; where it has formation, in fact, it weakens the vessel wall and may favor its rupture, a phenomenon from which an internal hemorrhage with an almost always fatal outcome derives; moreover, it is a risk factor for thrombo-embolic phenomena at the aortic level.
At present, the precise cause of abdominal aortic aneurysms is unknown; however, it is the unanimous opinion of the doctors that factors such as aging, atherosclerosis, hypertension, cigarette smoking, vasculitis and genetic predisposition to abdominal aortic aneurysm have a decisive influence on the phenomenon in question. .
