Co-payment: A payment made by an individual who has health insurance, usually at the time a service is received, to offset some of the cost of care. Co-payments are a common feature of HMO (Health Maintenance Organization) and PPO (Preferred Provider Organization) health plans in the US. Co-payment size may vary depending on the service, generally with low copayments required for clinic visits and higher payments for other services such as those received in an emergency department. Also called co-insurance.
Co-stimulation: An event in the immune system involving the delivery of a second signal by an antigen-presenting cell. The second signal rescues the activated T cell from anergy (which is a state of immune unresponsiveness), allowing the T cell to produce the lymphokines necessary for the growth of additional T cells. T cells are small […]
Coagulation: In medicine, the clotting of blood. The process by which the blood clots to form solid masses, or clots. More than 30 types of cells and substances in blood affect clotting. The process is initiated by blood platelets. Platelets produce a substance that combines with calcium ions in the blood to form thromboplastin, which […]
- Coagulation, laser
Coagulation, laser: The coagulation (clotting) of tissue using a laser. A coagulation laser produces light in the visible green wavelength that is selectively absorbed by hemoglobin, the pigment in red blood cells, in order to seal off bleeding blood vessels. There is also, for example, electrocoagulation and photocoagulation.
Coarctation: A narrowing, stricture, or constriction of an artery. The sides of the vessel at the point of a coarctation appear to be pressed together.
- Coarctation of the aorta
Coarctation of the aorta: Congenital constriction of the aorta that impedes the flow of blood below the level of the constriction and increases blood pressure above the constriction. Symptoms may not be evident at birth but may develop as soon as the first week after birth, with congestive heart failure or high blood pressure that […]