The Pulmonary Veins

The pulmonary veins return the arterial blood from the lungs to the left auricle of the heart. They are four in number, two for each lung. The pulmonary differ from other veins in several respects:

1. They carry arterial instead of venous blood.
2. They are destitute of valves
3. They are only slightly larger that arteries they accompany
4. They accompany those vessels singly

They commence in a capillary network upon the walls of the air cells, where they are continuous with the capillary ramifications of the pulmonary artery, and uniting together, from one vessel for each lobule. These vessels uniting successively, from a single trunk for each lobe, three for the right and two for the left lung. The vein from the middle lobe of the right lung generally unite with that from the upper lobe, forming two trunks on each side, which open separately into the left auricle. Occasionally they remain separate; there are then three veins on the right side. Not infrequently the two left pulmonary veins terminate by a common opening.

Within the lung, the branches of the pulmonary artery are in front, the veins behind, and the bronchi between the two.

At the root of the lung, the veins are in front, the artery in the middle, and the bronchus behind.

Within the pericardium, their anterior surface is invested by the serous layer of the membrane. The right pulmonary veins pass behind the right auricle and ascending aorta and superior vena cava; the left pass in front of the thoracic aorta with the left pulmonary artery.

Right Ventricle

The right ventricle is triangular in form, and extends from the right auricle to near the apex of the heart. Its anterior or upper surface is rounded and convex, and forms the larger part of the front of the heart. Its under surface is flattened, rest upon the Diaphragm, and forms only a small part of the back of the heart. Its posterior wall is formed by the partition between the two ventricles, the septum ventriculorum, so that a transverse section of the cavity presents a semilunar outlined. The surface of the septum is convex and bulges into the cavity presents a semilunar outline. Its upper and inner angle is prolonged into a conical pouch, the infundibulum, or conus arterious, from which the pulmonary artery arises. The walls of the right ventricle are thinner than those of the left, the proportion between them being as 1 to 3. The wall is thickest at the base, and gradually becomes thinner toward the upex. The cavity equals in size that of the left ventricle, and is capable of containing about three fluidounces.

The following part presents them for examination:
.....................Auriculo-ventricular
Openings { Opening of the pulmonary artery


Valves { Tricuspid
................Semilunar

And muscular and tendinous apparatus connected with the tricuspid valve:
Colunae carneae
Chordae tendineae