Each blowhole leads to an air passage that leads to a baleen whale's trachea and then to its lungs. Baleen is an adaptation for filter-feeding. In baleen whales, stiff plates of baleen grow down from the gums of the upper jaw. The baleen plates are arranged in rows that extend down each side of the mouth. It is strong, yet elastic.
Baleen plates arise in the fetus as thickenings of skin on the upper jaw.
At birth, baleen is soft and short, but it soon stiffens. The frayed edge of each plate intertwines to form a mat which functions as a strainer during filter feeding. Gray whales have about 130 to 180 baleen plates on each side. The right whale family, notably the bowhead whales, have the longest baleen. Baleen plates range in color from black to yellow or white, depending on the species.