Tom Williams, a teaching assistant in anatomy class, picked up a bone and pretended it was a telephone. He put the big hole in this bone up to his ear and said, “Hello, obturator, obturator (operator,...

Tom Williams, a teaching assistant in anatomy class, picked up a bone and pretended it was a telephone. He put the big hole in this bone up to his ear and said, “Hello, obturator, obturator (operator, operator).” Name the bone and the structure he was helping the students to learn.