Porcupine quills are the sharp spines that cover the body of a porcupine. These spines are made of keratin, the same material that makes up human hair and nails. The quills are used for defense against predators, and can be released when the porcupine feels threatened. The quills can also be used for other purposes, such as sewing and decoration. The term 'spines' is an appropriate description for these quills, as they are long and thin and have a pointed end.