...as far as glass arrowheads, obsidian is volcanic glass and many animals have been killed with obsidian heads as well as beer bottle glass heads, 1/4" thick window glass, TV picture tube glass and many other sources. Heck, even flint(generically speaking) arrowheads can be chipped when a bone is struck.
...and even a metal broadhead can crack and break when bone is hit.
If the arrow is shot through or into the ribcage very little meat is adversely affected.