Pesachim 83B

שמצאן צבורין צבורין, ומהן חלוצין. עצמות קדשים דאין בהן משום שבירת העצם ⁠— לכולהו הוה חליץ להו ואכיל להו, ולא בעי שריפה.

when one finds them in piles, and he sees that some of them have had their marrow removed. If these bones are bones of offerings to which the prohibition of breaking a bone does not apply, one can assume that the owner removed the marrow from all the bones before the marrow became leftover and ate it, and they do not require burning.

עצמות הפסח דיש בהן משום שבירת העצם ⁠— דילמא הני דחלצינהו, ולהנך לא חלצינהו, ובעי שריפה.

On the other hand, with regard to the bones of the Paschal lamb, to which the prohibition of breaking a bone does apply, perhaps the owner removed the marrow from these, and from those he did not remove the marrow, and they require burning. Therefore, although one needs to check all the bones of the Paschal lamb he finds to ensure that they do not have marrow left in them, he does not need to burn them due to the unconfirmed possibility that the marrow was removed after it became leftover. The bones would need to be burned only if there was still marrow in them or if one knew for certain that they had served as a base for leftover sacrificial meat.

אמר רב יהודה אמר רב: כל הגידין בשר, חוץ מגידי צואר.

Rav Yehuda said that Rav said: All the sinews in an animal are considered like meat. Therefore, one can fulfill his obligation to eat the Paschal lamb by eating them and one can register for them, except for the sinews of the neck, which are so hard that they are not considered meat.

תנן: העצמות והגידים והנותר ישרפו בששה עשר. הני גידין היכי דמי? אילימא גידי בשר ⁠— ניכלינהו? ואי דאיתותר ⁠— היינו נותר? אלא פשיטא: גידי צואר.

We learned in the Mishnah: The bones, and the sinews, and the leftover should be burned on the 16th. The Talmud asks: What are the circumstances in which these sinews must be burned? If we say they are sinews of meat, let us eat them. Why are they burned? And if they are sinews that were left over and not eaten for some other reason, they are leftover, so why does the Mishnah list sinews separately? Rather, it is obvious that the Mishnah is referring to sinews of the neck, which are different than other sinews and are therefore mentioned separately.