The expressions of these prime feelings are instinctual, the muscle relationships and actions are involuntary. In general, the facial muscles are delicate, finely attuned and easily seen because they lie just under the surface.

The facial muscles not only communicate moods and expressions they also display sympathetic characteristics. For instance, when we are threading a needle we often pucker our lips to "aid" the thread through the needle's eye.

All facial expressions involve the muscles and other regions of the mouth. Therefore, to recognize the facial expressions we must first recognize the mouth which is more than just the pink lips.

The mouth part extends from the bottom of the nose to the Mentolabial Sulcus, i.e., the sulk-line of the chin. The mouth is a convex form and wraps around the muzzle of the face.

Sketching the mouth should always start with the articulation of the Interstice, i.e., the horizontal line where the upper and lower lips meet. The lips wrap around the convex protuberance of the dental curve and the interstice roughly corresponds to the middle segment of the front, upper teeth.

Note that the Nodes in the corners of the mouth are lower than the middle of the interstice, except in a smile when the facial muscles pull up the nodes.

The lips, or Labia, are put together with mucous membrane whose pinkness results from the blood capillaries lying just under the surface.

The upper lip has three forms. In the middle is the Tubercle which is non-muscular and add to the 'V' shape of the top where it meets the bottom of the Philtrum. The Philtrum is the stretched, vertical channel that extends from the bottom of the nose to the tubercle of the top.

The philtrum, which means "love drop", is bounded by ridges on each side. Practically every starting draftsperson overextends the philtrum, thus placing the mouth too low.

The other 2 parts of the upper lip are 2, horizontal stretched forms. The muscles here, however, are the observable ridges of the middle vertical fibers of the Orbicularis Oris whose action results in the puckering up of the lips. The various facial muscles fastened to the corners of the mouth do the pulling and pushing.

The upper lip is flatter than the bottom lip. It is a downward tilting plane and generally appears darker than the bottom lip. There is a small up-plane on the vermillion border of the top that quite often catches a soft light. For most people, the upper lip tucks into the nodes.

The bottom lip generally stops a little short of the nodes. The bottom lip is heavier and fuller. It consists of two stretched forms that give it a more squared-off look than the upper lip.

Slightly below the vermilion border of the bottom lip is a elevated edge that develops laterally and is more obvious at the corners.

The vermilion border of the bottom lip should not be sketched with a distinct line, it has to be suggested more than sketched. Or else it will look like lipstick.

The bottom lip is an up-plane and will often catch a highlight. Like the upper lip, the ridges of the middle vertical fibers of the orbicularis oris form the texture of the bottom lip.

The bottom of the mouth area is at the mentolabial. Forming at the bottom edge of the lower lip's two stretched forms are two columnar tubes that radiate diagonally downward. These are the Pillars of the Mouth. This is a down plane and thus will lie in shadow.

With this we end the complete account of the elements that make the mouth and in the end the smile.