The structure and parameters of the abdominal aorta

What is the abdominal aorta and where is it located?

As you know, the largest human artery - the aorta - consists of several sections. Most of them are located within the chest. Only one part (abdominal or abdominal) passes into the abdominal cavity, under the diaphragm. Throughout it is located in front of the spine and nourishes the entire lower half of the body with arterial blood.

Abdominal aorta anatomy

Topographically, this vessel begins at the level of the 12th thoracic vertebra, leaving the aortic opening of the diaphragm. In the abdominal cavity, the aorta is displaced anteriorly from the spinal column, slightly to the left of the midline. Throughout its entire length, the vessel gives off multiple branches that feed the structures of the abdominal cavity.

The size of the abdominal aorta is normal:

• length - from 13 to 15 cm;
• diameter - 18-20 mm.

The abdominal aorta ends at the level of the 4th or 5th lumbar vertebra, at the point of bifurcation (i.e., bifurcation), where it diverges into the right and left iliac arteries.

Behind the abdominal aorta is the spine, in front - the mesentery root of the small intestine, pancreas and duodenum. On the right is the inferior vena cava, and on the left is the left adrenal gland and kidney.

The branches of the abdominal region are divided into parietal (feeding the abdominal wall) and visceral (feeding the internal organs).

The first group includes such paired arteries:

• lower diaphragmatic;
• lumbar (4 on each side);
• unpaired sacral.

Visceral branches are paired and unpaired.

Couples include:

• middle suprarenal;
• renal (renal);
• testicular (in women - ovarian), which supply blood to the genitals.

Unpaired branches:

• celiac trunk, which gives branches to the liver, stomach, spleen;
• upper and lower mesenteric, feeding all parts of the intestine.

In the photo you can see the layout of the outgoing branches:

Microscopic structure

Like the entire aorta, the abdominal section refers to elastic-type arteries, the wall of which consists of three functional membranes:

1. Intima is the inner layer that has a protective, nourishing and regulating function. The membrane is represented by epithelial cells - endothelial cells, which are most exposed to pathological influences, including lipid deposition, and this is the cause of atherosclerosis.
2. Media is the middle layer that provides mechanical strength and extensibility to the vessel to maintain constant pressure. The sheath is composed of connective tissue containing elastic and collagen fibers.
3. Adventitia is an outer shell that provides a protective function. It is represented by cells of connective tissue, but denser, to create high strength. In addition, it contains nerve fibers and capillaries (called vasa vasorum).

The above layers are not very tightly connected, due to which dissecting aneurysms can form.

What function and tasks does it perform?

This vessel is very important as it supplies oxygen and nutrient-rich blood to the entire abdominal cavity and lower extremities. In fact, such an aorta fully ensures the functioning of the digestive and genitourinary systems of the body, because the pathology of the vessel can lead to disruptions in the work of the corresponding organs.

In addition, this vessel also plays a significant role in maintaining normal blood pressure due to its elastic properties. At the moment of contraction of the heart, a large volume of blood stretches the wall; during relaxation, it returns to its original position. This mechanism prevents too great a gap between systolic and diastolic blood pressure.

Blood flow is greatly influenced by the condition of the walls of the aorta. Normally, a laminar (or linear) blood flow should be observed. However, in the presence of any protrusions (or vice versa, pockets, niches), vortices appear, which causes a turbulent (chaotic) current. There is a large frictional force in it, which slows down the speed and leads to a violation of hemodynamics and perfusion (blood supply) of tissues.

The most common pathological conditions and their complications

Cardiovascular diseases are among the top three causes of death. The group of disorders includes diseases of the aorta, including its abdominal section.

There are such diseases of the abdominal aorta:

1. Atherosclerosis obliterans is the most common disease that occurs as a result of lipid metabolism disorders. It is characterized by the deposition of protein-fat complexes in the inner membrane (intima) of the artery and the proliferation of connective tissue. Because of this, the elasticity of the vessel decreases, plaques are formed, which narrow the lumen and impede the movement of blood. Also, against the background of such a pathology, thromboembolic complications (most often mesenteric artery infarction) and renovascular hypertension may occur. For treatment, drug therapy (anti-cholesterol drugs), diet are used.
2. Aneurysm - this diagnosis is made if a local increase in the diameter of the vessel is found by more than 2 times. Most often it occurs due to hypertension. At the same time, blood flow worsens, blood clots can form. It is characterized by pain, throbbing in the abdomen. Treatment of pathology - planned or emergency surgery.
3. A dissecting aneurysm is characterized by a rupture of the intima, due to which blood flows between the layers of the wall, causing their further stratification and the formation of pathological cavities. It is considered the most dangerous form, since there is a very high probability of a complete breakthrough and death of the patient.
4. Arteriovenous aneurysm - usually caused by trauma, due to which a pathological connection is formed between the artery and vein, and there is a discharge of blood from the aorta. This leads to a significant overload of the right ventricle. As a result, heart failure and venous congestion develop.
5. Aortitis is an inflammatory disease of the artery wall due to bacterial or viral infection, autoimmune aggression. This is a common cause of aneurysms and thromboembolism.
6. Nonspecific aortoarteritis (Takayasu's disease) is an autoimmune inflammatory disease, as a result of which the vessel wall becomes sclerosed, and the perfusion of the lower extremities worsens. Renovascular hypertension is one of the complications of this pathology. In the initial stages, conservative treatment is used (glucocorticosteroids, symptomatic therapy); in the future, surgery may be required.
7. Leriche syndrome is a disease characterized by occlusion (narrowing) of the lumen of the distal abdominal aorta and its branches. This leads to ischemia of the corresponding organs. Most often it becomes a complication of such stenosing pathologies as atherosclerosis or nonspecific aortoarteritis. Another reason may be congenital defects.The classic symptoms are intermittent claudication, lack of peripheral arterial pulsation, and erectile dysfunction.
8. Mesenteric artery infarction is one of the most dangerous complications, which is characterized by ischemia of the visceral peritoneum and intestines as a result of blockage of the vessel by a thrombus. Cardiovascular diseases, congenital and acquired defects, rhythm disturbances lead to pathology. The result is tissue necrosis and peritonitis. Mortality is up to 60%.

Conclusions

As part of the aorta, the largest artery in the human body, its abdominal region plays an essential role in ensuring the normal functioning of the vascular system. In addition, the vessel supplies blood to important structures: the intestines, genitourinary organs and lower limbs. Obliterating diseases of the abdominal aorta lead to insufficient perfusion of the above organs and the development of ischemic changes, which can lead to complete or partial loss of function.