Dear Rohit, there is nothing such as important in MBBS. It is not like your 10th or 12th that you prepare on important topics leaving the rest. Anatomy is the study of bodily structure including bones, nervous system and everything as in whole. Unless you read about radial nerve, you will not know what is radial plexus and what causes Golfer's elbow. Everything is interlinked. So no topic is less important than the other.