The photograph shows the opening in the posterior wall of the atrium where the vena cava is attached. The right ventricle is located under the right atrium. This ventricle is large, thick walled and covered by surface fat deposits. Blood flows from the right atrium into the right ventricle through the right AV valve. After the ventricle fills with blood it contracts and then the AV valve closes preventing backflow into the atrium. With backflow prevented, the blood is forced to move onward through the pulmonary semilunar valve and into the pulmonary artery.
The forceps in the photograph extends from the upper region of the ventricle through the valve and into the pulmonary artery. The pulmonary artery carries blood deficient in oxygen and rich in carbon dioxide to the lungs. This blood vessel divides once in order to reach each lung. As blood passes through the lungs carbon dioxide is released and a new supply of oxygen enters the blood and immediately combines with hemoglobin. In the lung smaller blood vessels recombine to form a large pulmonary vein that returns the blood to the left atrium.
This is the only vein in the body that transports blood rich in oxygen. The left atrium collects blood returning from both lungs. It is also thin walled and small when compared to a ventricle. After filling, the atrium contracts forcing blood through the open left AV valve and into the left ventricle.
The left AV valve, like the one on the other side of the heart, prevents backflow of blood when the ventricle contracts. The left ventricle is the largest and most muscular heart chamber. When it contracts blood is forced under very high pressure out through the aortic semilunar valve and into the aorta. This blood vessel, the largest of all of the arteries, branches into a network of smaller arteries that transport blood to all parts of the body. Transgenic technology has potentially solved many of the immunological difficulties of using pig organs to support life in the human recipient.
Nevertheless, other problems still remain. Knowledge of cardiac anatomy of the pig Sus scrofa is limited despite the general acceptance in the literature that it is similar to that of man. A qualitative analysis of porcine and human cardiac anatomy was achieved by gross examination and dissection of hearts with macrophotography. The porcine organ had a classic 'Valentine heart' shape, reflecting its location within the thorax and to the orientation of the pig's body unguligrade stance.
The human heart, in contrast, was trapezoidal in silhouette, reflecting man's orthograde posture. The morphologically right atrium of the pig was characterised by the tubular shape of its appendage a feature observed on the left in the human heart. The porcine superior and inferior caval veins opened into the atrium at right angles to one another, whereas in man the orifices were directly in line.
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