This question is a follow-up to "Different-counts-of-the-248-organs-".
As we see from the Mishnah in Ohalot 1,8, only the bones are counted as organs, namely a bone that has a sinew and some flesh.
The Gemmorah in Bekhorot 45a states that women have 252 organs (there are different opinions, however, based on different Torah verses that range from 251-253):
מעשה בתלמידיו של ר' ישמעאל ... שבדקו ומצאו בה מאתים וחמשים ושנים:
אמר להם שמא באשה בדקתם שהוסיף לה הכתוב שני צירים ושני דלתות
With regard to the number of limbs or bones in the human body, Rabbi Yehuda says that Shmuel says: There was an incident involving the students of Rabbi Yishmael, who boiled the corpse of a prostitute who was sentenced by the king to death by burning, in order to separate her flesh from her bones. They examined and found she had 252 organs. They were puzzled by their finding, as the Sages say that the human body has only 248 limbs. Shmuel said to them: Perhaps you examined the corpse of a woman, as the verse added to her two hinges and two doors, for a total of 252 organs.
(As the whole discussion is within the topic of impurity I imply that the count in Bekhorot applies to the bones also as in Ohalot.)
I couldn't find any empirical support for this claim, as anatomically, the two skeletons are identical (with 206 bones, not 248-252). Also, this seems to be a very easy anatomical test - counting bones - there shouldn't be any dispute at all.
Interestingly, if women had 4 additional bones, R"I's students could easily identify the female skeleton just by those 4 bones (2 axles and 2 doors?), not by the total number of 252! (thanks to DonielF)
So what is going on here with counting the female skeleton differently?