Pig hearts are very similar in size, anatomy and function to human hearts, so are used to train medical students. Porcine hearts are the gold-standard in pre-clinical animal testing for all cardiovascular devices prior to use in humans to both test the safety and efficacy, and refine the implant procedures.
In the past month, researchers transplanted pig hearts into two people who had suffered catastrophic heart failure and were left brain dead but remained on life support.
Another question is how long – and how well – a pig's heart can work in a human host. Human heart transplants are highly successful with a one-year survival rate of 91%.
Nonhuman primates (apes and monkeys) are most like humans anatomically and physiologically.
Although pig hearts are markedly similar to human hearts, there are subtle differences in the anatomy. We have found the diameter of the great vessels to be proportionally smaller in pigs than in humans, particularly for the ascending aorta and main pulmonary artery (PA).
Pigs like other mammals have a four-chambered heart. The right side of the heart pumps blood to the lungs (pulmonary circulation), and the left side pumps blood out to the rest of the body (systemic circulation).
A human heart is very similar to a beef heart, thus allowing in-depth discussions related to the similarities and differences. Both serve the same purpose: to oxygenate blood from the lungs to the heart and pump it through the body, and both have four valves and four chambers.
The brain is the only organ in the human body that cannot be transplanted. The brain cannot be transplanted because the brain's nerve tissue does not heal after transplantation.
Chimpanzees
We share 99 percent of our DNA with chimpanzees, so it comes as no surprise that countless hours of research have been dedicated to understanding the intelligence and behavior of our sister species. This research has firmly established that chimps are one of the most intelligent species on earth.
Naturally, most of our common traits come down to anatomy. Dogs breathe with lungs and have hearts that circulate blood the same as we do. They have most of the same organs as humans, like a brain, liver, stomach, and intestines. Dogs even have prostates, although they do not have an appendix.
Watershed moment in animal-to-human transplants
This world-first case showed that an animal heart can survive in a human without being rejected immediately. The University of Maryland School of Medicine (UMSOM) released a short graphic YouTube video of the procedure.
The size and anatomy of the pig heart is roughly the same as human, though there are considerable differences (see below). Pigs can be bred intensively, with large litters, meaning the number of available organs could be increased rapidly.
Heart. How long transplants last: Median survival is greater than 12.5 years and has gotten better each decade.
One problem, however, is that pigs, like most mammals, have a sugar molecule called alpha-gal that humans (and some nonhuman primates) do not. The human immune system produces a severe immune reaction to alpha-gal, leading the body to reject the transplanted organ.
Because those busted capillaries fed the heart with oxygen, cardiac muscle cells began to die in their absence. On day 60, Griffith's team withdrew life support because Bennett's heart had been irreversibly damaged.
CHIMPANZEES. RECKONED to be the most-intelligent animals on the planet, chimps can manipulate the environment and their surroundings to help themselves and their community.
Humans have the highest EQ at 7.4, but bottlenose dolphins have EQs of 5.3, significantly higher than all other animals.
The great apes are considered to be the smartest creatures after humans. Among them, orangutans stand out as being especially gifted with brain.
The brain and nerve cells require a constant supply of oxygen and will die within a few minutes, once you stop breathing. The next to go will be the heart, followed by the liver, then the kidneys and pancreas, which can last for about an hour. Skin, tendons, heart valves and corneas will still be alive after a day.
You can still have a fairly normal life without one of your lungs, a kidney, your spleen, appendix, gall bladder, adenoids, tonsils, plus some of your lymph nodes, the fibula bones from each leg and six of your ribs.
Although some patients who have a diseased portion of their liver removed are unable to regrow the tissue and end up needing a transplant. Researchers from Michigan State University believe blood clotting factor fibrinogen may be responsible.
Canine hearts have numerous pulmonary veins, ranging from 4 to 8, returning blood from the lungs to the left atrium (1). Similar to human hearts, the left azygous vein is not present in the canine heart (1). Unlike the human heart, the Thebesian valve does not cover any part of the coronary sinus ostium (1).
Like a human heart, a pig heart consists of four chambers: two atriums and two ventricles. Likewise, consistent with the structure of a human heart, it has four valves and an aorta. These similarities allow blood to flow through a pig's heart in the same way it flows through a human's heart.
The sheep heart is more ventrally tilted along its long axis than is the human heart and has a relatively blunt apex formed entirely by the left ventricle. Whereas the normal heart weight:body weight ratio in adult humans has been reported to be 5 g/kg,37 the ratio in sheep is 3 g/kg.