Anatomical term indicating direction. With reference to quadrupeds, rostral indicates the direction toward the head and is used synonymously with anterior. The opposite direction is caudal, indicating direction toward the tail and is used synonymously with posterior. In human anatomy, rostral 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, rostral, or alternatively anterior, it indicates direction toward the face. In contrast, caudal, or posterior, it indicates direction toward the back of the head.