Nice game, though it felt a little 'usual'.
The graphics, I must say, were awesome, especially in the opening screen. Normally, I would dislike the whole belching thing going on in the background, but since the theme was all about innards, it was more or less appropriate.
My only problem was that it felt.. not as unique as I would like a game to be. Manuevering around, avoiding stuff.. Same old, same old. More power ups, more options.. more sounds? Many things could make this better, but it's also good as-is! Good job on the game!