The pig’s cardiovascular system is a subject of scientific interest, as its heart and circulatory network are central to advancing our understanding of cardiovascular science. The biological parallels between pigs and people have positioned swine as an important resource in the effort to treat human heart disease. This connection forms the basis for a field of study that could reshape medical treatments.
Anatomy and Function of the Pig Cardiovascular System
The pig’s cardiovascular system transports nutrients, gases, and waste throughout the body. At its center is a four-chambered heart that functions as a muscular pump. This organ is divided into two upper chambers, the atria, and two lower, more muscular chambers called ventricles. The heart’s contractions propel blood through a vast network of vessels.
Blood circulation in the pig is organized into two primary circuits: the pulmonary and the systemic. The pulmonary circuit carries deoxygenated blood from the right side of the heart to the lungs, where carbon dioxide is exchanged for oxygen. This newly oxygenated blood then returns to the left side of the heart.
From the left side of the heart, the systemic circuit begins, pumping oxygen-rich blood out through the aorta, the body’s largest artery. The aorta branches into smaller arteries, which lead to microscopic capillaries that permeate the body’s tissues. Here, oxygen and nutrients are delivered to the cells, and waste products are collected before the deoxygenated blood returns to the right side of the heart through veins.
Comparison to the Human Cardiovascular System
The utility of the pig in studying human health stems from the similarities between the two cardiovascular systems. The pig heart’s size, as a ratio of total body weight, is nearly identical to that of a human, at approximately 5 grams per kilogram in young pigs. Both species possess a four-chambered heart structure, with two atria and two ventricles that function in a comparable manner.
This resemblance extends to the coronary arteries, the vessels that supply blood to the heart muscle. The distribution, size, and pattern of these arteries in pigs closely mirror those in humans. Physiological data such as heart rate, which averages 90-107 beats per minute in pigs and 70-100 in humans, and blood pressure also show strong parallels.
Comparisons also reveal similarities in the finer details of the circulatory system. For instance, the way cholesterol is distributed in the blood, with about 60% as low-density lipoproteins in pigs and 63% in humans, is alike. While there are anatomical differences, such as the number of pulmonary veins entering the left atrium (two in pigs, typically four in humans), the functional and structural overlaps are substantial.
Role in Biomedical Research and Medicine
The anatomical and physiological similarities between pig and human cardiovascular systems have established the pig as a model in biomedical research. This is evident in xenotransplantation, the process of transplanting organs from one species to another. The pig heart is a leading candidate for transplantation into human patients with end-stage heart failure. Recent advancements in genetic engineering aim to overcome the immunological rejection that has historically been a major barrier.
Pigs are also frequently used to test the safety and effectiveness of new medical devices before they are approved for human use. Devices such as coronary stents, which are used to open blocked arteries, and artificial heart valves are often evaluated in pigs. This allows researchers to observe how these devices perform under realistic physiological conditions.
The pig model also provides a platform for developing and refining surgical techniques. Surgeons can practice complex cardiac procedures, perfecting their methods in a setting that closely mimics the human anatomy. This hands-on training can improve surgical outcomes and patient safety when the techniques are applied in clinical practice.
Common Cardiovascular Diseases in Swine
Pigs are also susceptible to their own set of cardiovascular diseases. One notable condition is mulberry heart disease, a nutritional disorder caused by a deficiency in vitamin E and selenium. This disease affects fast-growing young pigs and leads to sudden death due to damage to the heart muscle.
Bacterial infections can also impact the swine cardiovascular system, leading to conditions like vegetative endocarditis. This occurs when bacteria colonize the heart valves, forming growths that can interfere with normal blood flow and valve function. Pericarditis, an inflammation of the sac surrounding the heart, is another common finding, often resulting from systemic infections.
Like humans, pigs can also be born with congenital heart defects. Studies have identified various structural anomalies, including atrial and ventricular septal defects (holes in the walls separating the heart chambers) and malformations of the heart valves.