- anticoagulant: substance that hinders the clotting of blood
- bacteria: microorganisms capable of varied chemical metabolic transformations
- cardiovascular disease: diseases of the heart and blood vessels
- enzyme: substance that speeds up or slows down a chemical reaction without being changed itself
- fibrinogen: globulin produced by the liver and present in blood plasma; is the main agent in the formation of blood clots
- hemetin: enzyme secreted by the Amazon leech that dissolves clots already formed
- hirudin: enzyme in the gut of the medicinal leech that prevents blood from clotting