Complex sentence: With regard to biology, flesh is the soft substance of a human or other animal body that consists of muscle and fat; for vertebrates, this especially includes muscle tissue (skeletal muscle), as opposed to bones and viscera.
Split into simpler sentences: With regard to biology, flesh is the soft substance of the body of a living thing. In a human or other animal body, this consists of muscle and fat; for vertebrates, this especially includes muscle tissue (skeletal muscle), as opposed to bones and viscera.