And further how exactly did physicians in ancient times work? Did they have explicit knowledge about the body or were they mostly charlatans?
Would be great if anyone could at least answer one question, I'm very curious :)
Some ancient knowledge was preserved in monasteries in Europe and to a greater degree by Islamic Scholars in the Middle East.
It's a bit of a long-running myth of some "Christian Dark Ages" where most knowledge was destroyed, most scientists were burned as witches (in spite of that never once happening) and if the Church was painted in a positive light, then its attempts to salvage knowledge were depicted as "failures" instead of being outright ignored.
In truth there was legitimate scientific advancement in the medieval European world. Most of this was in the realm of architecture. Notre Dame officially opened in 1345, Europeans became masters of defensive fortifications and siege warfare, Christian Theologians translated some great Greek and Arabic works into Latin and tried to merge ancient philosophy into modern Christian thinking.
As for medicinal science, the Islamic world had the Christian world beat by miles, with doctors there capable of performing even primitive cataract surgery.
It's important to note that Science didn't stop in the medieval world, though there were quite a few mistaken theories that became "in vouge" for a while; even things like Geocentric models of the star system had some "evidence" back then, at least from the understanding of the people of the time. No one really went "The sun revolves around the earth 'cuz it just looks like that and Jesus would make it so", they at least tried to adhere to principles of evidence and scholarly inquiry.
If you want specific examples of medicinal ideas at the time, "Humorism" was a concept mostly derived from ancient Greek and Roman physicians, which held the body had 4 "humors" that, when out of balance, would cause various physical ailments.
A lot of this science was mixed haphazardly with some vaguely supernatural leanings, but in all fairness Germ Theory was a relatively new invention. "Tiny invisible blob-things that can be transferred by touch and make you sick" would sound about as sensible as "Demons are doing it" to the people of the time.