Galen of Perganum (born AD 129, , Pergamum, Mysia, Anatolia [now Bergama, Tur.]
died c. 216 ) was one of the first, who named some parts of the human body - and as a continuation of earlier Hippocratic conceptions, Galenic physiology became a powerful influence in medicine for the next 1,400 years.
Most parts of the human body have been named the same since about that early time. During the Middle Ages Mostly students of medicine just looked for those parts described by Galen (which were mostly those of animals [dogs]), but by the end of the Middle Ages some of his ideas had been corrected.
Many functions - opposite to what Wy says - were known already before the Middle Ages.
History of medecine