The food is moved along the gut by the action of two sets of muscles. One set runs along the gut and the other set runs around it, as you can see in the next video.
The combined activity of these muscles produces ‘waves’ of contraction that push the food along (peristalsis). This enables you to eat and drink, and for the digesting food to travel along your gut, while you are lying down or even while standing on your head. The muscles work best if the food you eat contains plenty of fibre.