Kidneys

The kidney's have a higher blood flow than even the brain, liver or heart.  A small percentage of the population (approximately .07 percent) are born with more than two kidneys. An even smaller percentage (about .02 percent) are born with only one kidney.  The average adult kidney can process up to three gallons of liquid in a two-hour period. Of all organs, kidneys are most in demand and the most frequently donated.  Most diseases that affect the kidneys affect both at the same time, so a living donor is generally not at a greater health risk with only one kidney.

Eyes

Eyes are the most complex organs you possess except for your brain. They are  composed of more than two million working parts and can process 36,000 bits of information every hour.  They contribute towards 85% of your total knowledge and utilize 65% of all the pathways to the brain.  Eyes can instantaneously set in motion hundreds of muscles and organs in our body.  In a normal life-span, our eyes can bring almost 24 million images of the world around us.  The external muscles that move around the eye are the strongest muscles in our body for the job that they have to do.  They are 100 times more powerful than they need to be. The eye is the only part of the human body that can function at 100% ability at any moment, day or night, without rest. Your eyelids need rest, the external muscles of your eyes need rest, the lubrication of your eyes requires replenishment, but your eyes themselves never need rest.

Liver

The liver is necessary for vitamin storage, removing waste from blood and digestion.

The liver is the only organ that can grow cells in order to regenerate itself. A liver can actually be split in two and transplanted into two different people. A living person can have a portion of the liver removed, and the remaining portion will regenerate to almost its full previous size. The liver also generates the most heat of any organ in the body. Livers can be transplanted into a patient without removing the patient's own liver.

Heart

The heart, which weighs 7 -15 ounces, in an adult, consists chiefly of muscle and can perform enough work in one hour to lift 3,000 pounds, roughly the weight of a small car, about one foot off the ground. The heart is like a miniature pump, pumping blood through more than 60,000 miles of blood vessels.  That’s enough to circle the equator twice and then some.  The human heart can create enough pressure that it could squirt blood at a distance of thirty feet. In one day, the heart pumps nearly 2,000 gallons of blood. In a 70-year lifetime, it pumps about 51 million gallons.  The human heart is fully developed about eight weeks after conception, when the embryo is only about one inch long. The heart actually begins to beat even earlier: about four weeks after conception.  A heart will beat about 2.5 billion times in the course of an average lifetime. Once removed from the donor's body, a heart can only survive for about four hours.

Lungs

Humans have two lungs, with the left being divided into two lobes and the right into three lobes. They breathe in air, then extract the oxygen and pass it into the bloodstream, where it's rushed off to the tissues and organs that require it to function.   The total amount of air in the respiratory system is about 4 litres in a child and upto 6 litres in an adult.  About 1 litre of air always stays in our lungs no matter how hard we breathe out.  The right lung of a human is larger than the left one.  This is because of the space and placement of the heart.  Single or double-lung transplants can be performed. Additionally, living donors can donate a single lobe from the lungs, though it will not regenerate.

Pancreas

The pancreas is a gland organ in the digestive and endocrine system of vertebrates.   It is an organ near your stomach that makes insulin. Insulin helps the cells in your body process sugar. The pancreas also makes digestive juices.  Because the pancreas is a storage depot for digestive enzymes, injury to the pancreas is potentially very dangerous. A puncture of the pancreas generally requires prompt and experienced medical intervention. Pancreatic cancer, particularly cancers of the Exocrine Pancreas remain one of the most deadly cancers, and the mortality rate is very high. It's possible to make a living donation of a portion of the pancreas and still retain pancreas functionality.