Anatomical term indicating direction. With reference to quadrupeds, caudal indicates direction toward the tail and is used synonymously with posterior. The opposite direction is rostral, indicating direction toward the head and is used synonymously with anterior. In human anatomy, caudal is only commonly used in reference to the embryo and the brain and cranium. Due to the tilting of the central nervous system, for reference to the brain, caudal, or alternatively posterior, indicates direction toward the back of the head. In contrast, rostral, or anterior, indicates direction toward the face.