What is the Difference Between Thoracic and Abdominal Aorta

The main difference between thoracic and abdominal aorta is that thoracic aorta levels are from T4 to T12, whereas abdominal aorta levels are from T12 to L4 vertebra. 

The thoracic and abdominal aorta are two of the four sections of the aorta, which is the body’s main artery. They are elastic arteries. 

Key Areas Covered

1. What is Thoracic Aorta
– Definition, Facts, Features
2. What is Abdominal Aorta
– Definition, Facts, Features
3. Similarities Between Thoracic and Abdominal Aorta
– Outline of Common Features
4. Difference Between Thoracic and Abdominal Aorta
– Comparison of Key Differences
5. FAQ – Thoracic and Abdominal Aorta
– Answers to frequently asked questions

Key Terms  

Abdominal Aorta, Thoracic Aorta

What is Thoracic Aorta

The thoracic aorta is the first of the two descending aorta. It spans from level T4 to level T12. Also, it continues from the aortic arch. Initially, it begins from the left of the vertebral column while approaching the midline as it descends. Furthermore, it runs through the aortic hiatus in the diaphragm, leaving the thorax. And, it continues with the abdominal aorta.

Figure 1: Sections of Aorta

Branches of the Thoracic Aorta

• Bronchial arteries: A pair of visceral branches, which arise laterally to supply bronchial and peribronchial tissue and visceral pleura. Only the left bronchial artery arises directly from the aorta. However, the right bronchial artery arises from the third posterior intercostal artery.
• Mediastinal arteries: They are small arteries, which supply blood to the lymph glands and loose areolar tissue occurring in the posterior mediastinum. 
• Esophageal arteries: Unpaired visceral branches of esophageal arteries arise anteriorly, supplying blood to the esophagus.
• Pericardial arteries: Unpaired visceral arteries, which supply blood to the dorsal portion of the pericardium.
• Superior phrenic arteries: Paired parietal branches, which supply blood to the superior portion of the diaphragm. 
• Intercoastal and subcoastal arteries: Small paired arteries, which branch off throughout the length of the posterior thoracic aorta. The subclavian artery supplies blood to the first and the second intercostal arteries. The remaining nine pairs of intercostal arteries supply blood to the intercostal spaces. Also, the subcoastal arteries supply blood to the flat abdominal wall muscles.   

What is the Abdominal Aorta

The abdominal aorta is the second of the two descending aorta. It spans from the level T12 to the L4 vertebra. Also, it continues from the thoracic aorta. Terminally, it divides into two arteries, the right and left common iliac arteries, which supply blood to the lower parts of the body.

Figure 2: Aortic Branches

Branches of the Abdominal Aorta

• Inferior phrenic arteries: Paired parietal arteries, which arise posteriorly at the level of T12. They supply blood to the diaphragm.
• Coeliac artery: A large, unpaired, visceral artery which arises at the level of T12. Another name for the coeliac artery is the celiac trunk. It supplies blood to the liver, stomach, spleen, abdominal esophagus, superior duodenum, and superior pancreas.
• Superior mesenteric artery: A large unpaired visceral artery, which arises at the lower level of L1 below the celiac artery. It supplies blood to the distal duodenum, jejunum-ileum, ascending colon, and part of the transverse colon.
• Middle suprarenal arteries: Small, paired visceral arteries, which arise at the level of L1, supplying blood to the adrenal glands.
• Renal arteries: Paired visceral arteries, which arise between L1 and L2. They supply blood to the kidneys.
• Gonadal arteries: Paired visceral arteries, which arise at the level of L2. The testicular artery refers to the male gonadal artery, while the ovarian artery refers to the female one. 
• Inferior mesenteric artery: A large, unpaired visceral artery, which arises at the level of L3. It supplies blood to the large intestine from the splenic flexure to the upper part of the rectum.
• Media sacral artery: A unpaired parietal artery, which arises at the level of L4. It supplies blood to the coccyx, sacrum, and lumber vertebrae. 
• Lumbar arteries: Four pairs of parietal lumbar arteries between the levels of L1 and L4. They supply blood to the abdominal wall and spinal cord. 

Similarities Between Thoracic and Abdominal Aorta

• The thoracic and abdominal aorta are two of the four aorta sections.
• Both begin at the thoracic level.
• They have branches.
• Both are descending the aorta.   

Difference Between Thoracic and Abdominal Aorta

Definition

The thoracic aorta refers to the part of the aorta in the thorax, while the abdominal aorta refers to the part below the thorax. 

Level

Thoracic aorta levels are from T4 to T12, while abdominal aorta levels are from T12 to L4 vertebra. 

Branches

Bronchial arteries, mediastinal arteries, esophageal arteries, pericardial arteries, superior phrenic arteries, and intercostal and subcoastal arteries are the branches of thoracic artery, while inferior phrenic arteries, coeliac arteries, superior mesenteric arteries, middle suprarenal arteries, renal arteries, gonadal arteries, inferior mesenteric artery, median sacral artery, and lumber artery are the branches of abdominal artery.

FAQ: Thoracic and Abdominal Aorta

What is the difference between AAA and TAA?

An abdominal aortic aneurysm (AAA) occurs in the wall of the aorta within the abdomen, while a thoracic aortic aneurysm (TAA) occurs in the wall of the aorta within the chest.

What divides the aorta into thoracic and abdominal?

The descending aorta is the longest part of the aorta, further subdivided into thoracic and abdominal aorta. The diaphragm is the anatomical division between the two. 

Is the abdominal aorta a continuation of the thoracic aorta?

It is a continuation of the thoracic aorta. It begins at the diaphragm and ends by splitting into two to form common iliac arteries. It supplies oxygenated blood to all abdominal and pelvic organs and the legs.  

Conclusion

In brief, the thoracic and abdominal arteries are the two sections of the aorta. Thoracic aorta levels are from T4 to T12. Also, the branches of the thoracic aorta are the Bronchial, mediastinal, esophageal, pericardial, superior phrenic, and intercostal and subcoastal arteries. In comparison, abdominal aorta levels are from T12 to L4 vertebra. However, Inferior phrenic arteries, coeliac arteries, superior mesenteric arteries, middle suprarenal arteries, renal arteries, gonadal arteries, inferior mesenteric artery, median sacral artery, and lumber artery are the branches of the abdominal artery. Therefore, the main difference between thoracic and abdominal artery is their level and branches.         

References:

1. The aorta. TeachMeAnatomy. (n.d.-a). 

Image Courtesy:

1. “OLI – Drawing Parts of aorta in relation to heart and diaphragm – English labels” By rva – Own Work (CC BY-NC-SA) via Anatomy tool
2. “Aorta branches” By Mikael Häggström – Own Work (CC-BY SA 3.0) via Commons Wikimedia