"The human body does not have a mouth"

Amidst my serious blogs, this is one of my usual blabbers. This is a the result of a discussion my brother and I had a few months back. If you see a 3rd class or 4th class text book and have a look at the parts of the human body, you will find "mouth" being marked. We have all learnt and accepted that mouth is a part of the body. But consider the following argument.

What do you call as the mouth? Mouth is not the lips, not the jaws, not the palate, not the teeth, not the tongue. Mouth is the "space" enclosed by the jaws. If mouth were to be just "space", then how can you call mouth as a part of the human body? It obviously does not belong to the human body. Thus, the statement "Human body does not have a mouth" is true. In fact it is true that no animal in this world has a mouth. Then what is the use of calling all the animals as "vaayillaa jeevan"(entities without a mouth. They are referred to thus because they cannot speak). A human too is a "vaayillaa jeevan", isn't he?