The Relationship between the Heart and Lungs

As you proceed through this tutorial the back button can be used to return to the previous frame or you can reactivate the previous link.

***

The thoracic cavity lies dorsal to the pectoral muscles. To expose the thoracic cavity two incisions are made on either side of the sternum (Figures 1-2).

Reflect the ribs and note the membranous septum (arrow) that divides the cavity into right and left sides. The posterior region of the thoracic cavity is formed by the muscular diaphragm (arrow). The heart (arrow) lies in the fat filled septum. As seen in a ventral view the lungs fold ventrally toward the heart (Figures 3-4).

A closer look at the right lung reveals that is composed of three major lobes:

• Anterior - Figures 5-6
• Medial - Figures7-8
• Posterior - Figures 9-10 A small accessory lobe is associated with the right posterior lobe of the lung. The accessory lobe sits in the mediastinal septum and can only be seen once the septum is removed and the heart is reflected. The heart has been reflected toward the head making it easier to see the relationship of the lobes. The accessory lobe passes between the inferior vena cava (dark blue vessel) which transports blood low in oxygen to the right side of the heart and the esophagus. The pulmonary artery (arrow) brings blood low in oxygen to the lung and the pulmonary vein (arrow) returns blood high in oxygen to the lung. To the left of the accessory lobe is the esophagus. You will be able to see it more clearly when you examine the heart.

The left lung is also composed of three major lobes, but it lacks an accessory lobe.

• Anterior and Medial- Figures13-14
• Posterior - Figures 15-16

Examine the relationship between the heart and lungs (Figures 17).

Examine the circulation on the right side of the heart (Figures 18-19). The right side of the heart receives blood low in oxygen from the:

• superior vena cava (1)
• inferior vena cava (2)
• azygous vein (3)

The blood then travels toward the lungs through:

• coronary sinus (4)
• right atrium (5)
• right ventricle (6)
• pulmonary artery (7)
• right pulmonary artery (8)

Examine the circulation on the left side of the heart (Figures 20-21).
The white arrow indicates angle along which the right and left ventricle are seperated by a thick septum. Begin with the structures on the right side of the heart:

• right atrium (1)
• right ventricle (2)
• pulmonary artery (3)
• left pulmonary artery (4)
• right pulmonary artery (5)

Blood is oxygenated in the lungs before returning to the heart in the pulmonary vein which is not clearly shown. Oxygenated blood flows through:

• left atrium (6)
• left ventricle (7)
• aorta (8)
• brachiocephalic artery (9)
• left subclavian artery (10)

Also note the fat body (11) lying across the base of the aorta.

By reflecting the left lungs over the heart it is possible to see the trachea (white arrows), which splits before entering the left medial and accessory lobes of the lung.

Edited 7-26-07