costa: a riblike part of a plant or animal (such as a middle rib of a leaf or a thickened vein of an insect wing)
structure: a particular complex anatomical part of a living thing
aspirin: the acetylated derivative of salicylic acid; used as an analgesic anti-inflammatory drug (trade names Bayer, Empirin, and St. Joseph) usually taken in tablet form; used as an antipyretic; slows clotting of the blood by poisoning platelets