Difference Between Aorta and Vena Cava

Aorta and vena cava are two main types of blood vessels attached to the heart. The main difference between aorta and vena cava is that aorta carries oxygenated blood whereas vena cava carries deoxygenated blood. Aorta is the main artery that leaves the heart through the left ventricle. It supplies oxygenated blood throughout the body. Two types of venae cavae supply blood to the right atrium of the heart. They are superior vena cava and inferior vena cava. Superior vena cava drains deoxygenated blood from the head, arms, and other upper parts of the body while inferior vena cava drains that from the lower parts of the body.

Key Areas Covered

1. What is Aorta
     – Definition, Structure, Role
2. What is Vena Cava
     – Definition, Structure, Role
3. What are the Similarities Between Aorta and Vena Cava
     – Outline of Common Features
4. What is the Difference Between Aorta and Vena Cava
     – Comparison of Key Differences

Key Terms: Aorta, Blood Vessels, Heart, Inferior Vena Cava, Superior Vena Cava

What is Aorta

Aorta is the main artery of the body, which begins at the left ventricle of the heart. The aortic valve separates aorta from the heart and composes three leaflets. Further, it opens in each heartbeat, allowing one-way flow of blood from the heart to the aorta. The aorta is about one inch in diameter. The four sections of the aorta are the ascending aorta, aortic arch, descending thoracic aorta, and the abdominal aorta.

1. Ascending aorta – It is about 2 inches long. The coronary arteries branch off from the ascending aorta.
2. Aortic arch – It covers the heart and gives rise to the artery branches that supply blood to the head, neck, and arms.
3. Descending thoracic aorta – It travels down through the chest and gives rise to the arteries that supply blood to the ribs and the chest.
4. Abdominal aorta – It begins at the diaphragm. The branches of the abdominal aorta supply blood to the rest of the organs in the body. In the end, it divides into a pair of iliac arteries

Figure 1: Aorta

The aorta has a high blood pressure, which facilitates the flow of blood throughout the body. The normal systolic pressure (the amount of blood pressure during the contraction of the heart) is 120 mmHg, and the normal diastolic pressure (the amount of blood pressure when the heart is at rest) is 80 mmHg.

What is Vena Cava

Vena cava refers to the largest type of veins in the body, which drains deoxygenated blood from the body to the right atrium of the heart. The two types of venae cavae attached to the right atrium are superior and inferior vena cava. The two types of venae cavae are shown in figure 2.

Figure 2: Superior and Inferior Vena Cava

The left and right brachiocephalic veins fuse together to form the superior vena cava. Hence, it drains deoxygenated blood from the upper chest wall, arms, neck, and head to heart. The combining of the two iliac veins coming from the legs forms the inferior vena cava, which is the largest vein in the body.  The inferior vena cava drains blood from the lower parts of the body. Both superior and inferior vena cava open into the right atrium without valves.

Similarities Between Aorta and Vena Cava

• Both Aorta and vena cava are main blood vessels attached to the heart.
• The diameter of both aorta and vena cava is high.
• Both aorta and vena cava consist of the same structure of blood vessels, containing three layers: tunica externa, tunica media, and tunica intima.

Difference Between Aorta and Vena cava

Definition

Aorta is the main artery of the body, which begins at the left ventricle of the heart.

Vena Cava is the largest type of vein in the body, which drains deoxygenated blood from the body to the right atrium of the heart.

Type of Blood Vessels

Aorta is the main artery of the body.

Vena Cava is the main type of veins in the body.

Attached to

Aorta is attached to the left ventricle of the heart.

Vena Cava is attached to the right atrium of the heart.

Function

Aorta carries oxygenated blood throughout the body.

Vena Cava returns deoxygenated blood from the body into the heart. 

Number

Aorta: A single aorta begins at the left ventricle.

Vena Cava: Two types of venae cavae supply blood to the heart. They are superior vena cava and inferior vena cava.

Structure

Aorta has a thick wall and narrow lumen.

Vena Cava has a thinner wall and wider lumen.

Tunica Media

Aorta: The tunica media of aorta is thick.

Vena Cava: The tunica media of vena cava is thin.

Blood Pressure

Aorta: The blood pressure of aorta is higher.

Vena Cava: The blood pressure of vena cava is lower than that of the aorta.

Conclusion

Aorta and vena cava are the two types of main blood vessels attached to the heart. Aorta is the main artery of the body while the two main veins of the body are superior and inferior vena cava. Hence, aorta carries oxygenated blood throughout the body, starting from the left ventricle of the heart while vena cava drains deoxygenated blood from the body to the right ventricle of the heart. The main difference between aorta and vena cava is the type of blood they transport and its direction.

Reference:

1. Hoffman, Matthew. “Picture of the Aorta.” WebMD, Available here.
2. “Vena Cava.” Encyclopædia Britannica, Inc., 10 Oct. 2012, Available here.

Image Courtesy:

1. “Aorta Anatomy” By Luke Guthmann – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Relations of the aorta, trachea, esophagus and other heart structures” By ZooFari (CC BY-SA 3.0) via Commons Wikimedia