The heart

Anatomy, physiology
The heart is a fist-sized muscular organ that contracts rhythmically to pump blood throughout the body and ensure the supply of blood and oxygen to the whole body. Deoxygenated blood arrives from the circulatory system into the right section of the heart and then flows through the pulmonary circulation where the blood is saturated with oxygen. The oxygenated blood then flows into the left section of the heart from where it is pumped through the aorta into the circulatory system to supply the whole body with oxygenated blood. The heart's rhythm is based on electrical impulses. The conduction system delivers the impulse to the whole heart so that the myocardal muscle contracts.
Transplantation
Progressive heart failure, congenital heart defects and even viral infections can cause chronic cardiac insufficiency and weaken the heart muscle. This causes the heart to lose its ability to pump blood. Transplantation represents the final therapeutic option for patients who cannot be helped using medicines or surgery.
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Heart transplantation 

The liver

Anatomy, physiology
The liver is critical to the body's metabolic processes. It weighs approx. 1.5 - 2 kg. It is located on the right side of the upper abdomen and is divided into two lappets and several segments. Major functions performed by the liver include synthesis of proteins, utilization of food components and production of bile (elimination and discharge of metabolites, medicines and toxic substances). The liver is also responsible for producing coagulation factors, i.e. blood clotting will function properly only if the liver is healthy.
The liver is very well supplied with blood and can grow back to its normal size within a short time. This means it is also possible to transplant just part of the liver and to remove it and transplant it into old age.
Transplantation
The following causes can impair the functioning of the liver: Hepatitis B and C, cirrhosis of the liver, congenital defects of the liver, autoimmune diseases, liver tumours, poisoning due to medicines or mushrooms or alcohol abuse. All of these issues can impair the liver to the extent that it can no longer heal itself. A transplant is required in such cases.
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Liver transplantation

The lungs

Anatomy, physiology
The body has two lungs which are responsible for absorbing essential oxygen and eliminating carbon dioxide. Incoming air passes via the trachea into the bronchial tubes which branch off into smaller and smaller bronchial tubes before finally terminating in the pulmonary alveoli. This structure is known as the bronchial tree. The pulmonary alveoli are surrounded by tiny blood vessels. Oxygen is absorbed via their very thin membrane and carbon dioxide is released.
Transplantation
The following causes can make a lung transplant necessary: mucoviscidosis (cystic fibrosis), pulmonary emphysema, pulmonary hypertension and also rarer afflictions such as asbestosis (due to exposure to asbestos), sarcoidosis and inhalation of certain types of toxins. Patients are deemed to require a live-saving lung transplant if they can no longer manage the activities required during everyday life and need oxygen therapy.
Lungs can be transplanted individually or, as is more common, in pairs. In case of certain diseases, lung transplants are combined with heart transplants.
Lung transplantation

The kidneys

Anatomy, physiology
The functioning of the kidneys is primarily hormonal. They work to remove the final products of metabolism as well as various toxins from the body via the urine. They also help to ensure a proper water balance so as to regulate the blood pressure and the acid-base balance. The kidneys also produce hormones needed for haematopoiesis (formation of the cellular components that make up the blood).
Transplantation
The functions provided by the kidneys can be bridged through dialysis (removal of waste matter from the blood). However, a kidney transplant is desirable in many cases due to the substantial improvement in quality of life it offers by eliminating the need to undergo dialysis three times per week. Either the donor's right or left kidney is transplanted. It is common to simply leave the old kidneys in the body.
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Kidney transplantation

The pancreas

Anatomy, physiology
The pancreas is situated laterally in the middle of the abdomen between the spleen and liver. It terminates into the small intestine. The pancreas produces digestive juices which are released into the small intestine. The pancreas also contains what are known as "islets of Langerhans" which produce hormones (insulin, glucagon) in order to regulate the supply of sugar in the body.
Transplantation
The pancreas can be transplanted in its entirety, or it is also possible to transplant islets separately. A transplant can help to reduce or regulate the insulin supply so that the body's hormonal functions regain the ability to regulate themselves.
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Pancreas transplantation