M01.05.012 Great Vessels of the Heart

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Learning Objective

By the end of this lesson, you should be able to describe the anatomical course, relations, and major branches of the aorta, pulmonary arteries, pulmonary veins, superior vena cava, and inferior vena cava, and identify their key clinical correlations, including aortic dissection and aortic aneurysm.

The great vessels are the major arteries and veins directly connected to the heart. They are primarily located within the middle mediastinum and function to transport blood to and from the heart during systemic and pulmonary circulation.

Aorta

The aorta is the largest artery in the body and carries oxygenated blood from the left ventricle to the systemic circulation. It arises from the aortic orifice of the left ventricle and is separated by the aortic valve. The aorta has three major parts:

Ascending aorta – Lies within the pericardium and gives rise to the coronary arteries.
Arch of the aorta – Gives rise to three major branches:
- Brachiocephalic trunk
- Left common carotid artery
- Left subclavian artery
Descending aorta – Travels inferiorly through the thorax and passes through the diaphragm to become the abdominal aorta.

Activity

Clinical Relevance – Disorders of the Aorta

Aortic Dissection

Aortic dissection occurs when there is a tear in the inner wall (intima) of the aorta. Blood enters the vessel wall, creating a false lumen.

This can:

Reduce blood flow to distal organs
Weaken the vessel wall
Lead to aortic aneurysm formation

Aortic Aneurysm

An aortic aneurysm is a dilation of the aorta greater than 50% of its normal diameter. It may result from connective tissue disorders such as Marfan syndrome or secondary to dissection. The major risk is rupture, which can be rapidly fatal.

Pulmonary Arteries

The pulmonary arteries carry deoxygenated blood from the right ventricle to the lungs. They begin as the pulmonary trunk, separated from the right ventricle by the pulmonary valve. At approximately T5–T6, the trunk bifurcates into:

Right pulmonary artery – Larger and longer; supplies the right lung.
Left pulmonary artery – Supplies the left lung.

These vessels are located anterior to the ascending aorta before dividing.

Pulmonary Veins

The pulmonary veins return oxygenated blood from the lungs to the left atrium. There are four pulmonary veins:

Right superior
Right inferior
Left superior
Left inferior

They drain into the posterior aspect of the left atrium. The oblique pericardial sinus lies between the right and left pulmonary veins.

Superior Vena Cava

The superior vena cava (SVC) returns deoxygenated blood from structures above the diaphragm (except the heart and lungs) to the right atrium. It is formed by the union of the right and left brachiocephalic veins and drains into the right atrium at the level of the 3rd rib.

The SVC lies on the right side of the superior mediastinum before entering the middle mediastinum.

Inferior Vena Cava

The inferior vena cava (IVC) returns deoxygenated blood from structures below the diaphragm to the right atrium. It is formed by the union of the common iliac veins in the pelvis. It ascends through the abdomen, receiving blood from: