Baleen or whalebone is a filtering structure in the mouth of most whales, which they use to feed by sieving small animals from large mouthfuls of seawater. Instead of teeth, these whales have rows of baleen plates in the upper jaw–flat, flexible plates with frayed edges, arranged in two parallel rows, looking like combs with thick hair at the end of each comb tooth. Baleen is not in fact composed of bone, but of the protein keratin, the same substance as hair, horn, scales, claws and nails.
