dorsal

Adjective

• facing away from the axis of an organ or organism
  • the abaxial surface of a leaf is the underside or side facing away from the stem
    

• belonging to or on or near the back or upper surface of an animal or organ or part
  • the dorsal fin is the vertical fin on the back of a fish and certain marine mammals
    

Related words

• Antonyms: 
  adaxial , ventral