Ontogenetic development of the uncinate processes in the domestic turkey (Meleagris gallopavo).

Uncinate processes extend off the vertebral ribs in most species of bird. The processes are a crucial component of ventilatory mechanics, being involved in inspiration and expiration. Here we examine the pattern of ossification of the uncinate processes using histochemistry and biomechanical testing in developing domestic turkeys (Meleagris gallopavo). Ossification begins just before hatching, and the processes are fully ossified in the adult bird. We suggest that the development of these processes is linked to the onset of air breathing and the increase in sternal mass that occurs after hatching.