Serious question about a piece of meat
The white circle in the center is a bone, probably the femur. The muscles are covered with an external later of fascia, the epimysium (here's a question with some information). These layers separate muscles from each other, and often fat will also deposit in the spaces between muscles, which is what the white lines between muscle bellies are. There is also some cutaneous fat.

This is probably a section through the thigh, possibly a pig (though it looks a little too red). Regardless, the muscle will have the same basic layout as the image below of a pig thigh from pork.org, even if your image is from some other mammal.



You have to rotate your image clockwise about 45 degrees to get them to match up. The back of the thigh is at the top of the image.