by David Jon Kassan
Understanding the way the muscles of the mouth express the emotion of your subject is crucial in determining how to depict that emotion in your drawing. In this article I will touch upon the form concepts and muscular structure of the mouth and lips so that you can have some general guidelines in the back of your mind when you draw your next model. There are many variables to consider when drawing the lips. Everyone’s lips are unique; there are different sizes, shapes, and configurations that depend on the model’s size, age, ethnicity, and even eating habits. Luckily there are some common attributes as well, and they are helpful to keep in mind while drawing the mouth.
Visual Structure of the Lips
The lips are soft, movable, and very flexible. They are divided into two main parts, the upper lip (labium superioris) and lower lip (labium inferioris). In most cases the lower lip tends to be somewhat larger than the upper lip and is pillowy in its fullness compared to the upper lip. The upper lip usually falls into a form shadow because of its inward slant, which starts forward at its apex and ramps down and backward as its pulls inward, causing a slight overhang over the pillow shape of the lower lip. The lips can be broken down further into five distinct shapes. The upper lip may be divided into two wings on either side of the central beaklike shape. The little vertical indention just above the upper lip is called the philtrum.
The two lips together lay over the cylindrical shape of the muzzle of the mouth. Understanding this roundness of the overall form helps the artist depict how the center of the lips are closer to the viewer (on a straight-on view of the model) and thus how the corners of the mouth fold away from us in space, as if each side were attached to strings that were being pulled tight around a tin can.
The lips are really the transition point between our exterior facial skin and the inner smooth lining (or mucosa) of the mouth. This meeting point between these two tissues is called the vermilion zone. The name vermilion comes from the red color that is characteristic of this facial feature; this color is unique to humans and comes from the many blood vessels found in the dermis and their close proximity to the thin, translucent epidermis that covers them. The skin of the lips are only three to five cellular levels thick, compared to other facial-skin areas that are as many as 16 layers thick. The ridges found in the lips are a result of a highly folded dermis that is not found in the skin of any other body parts.
Muscular Structure of the Mouth
The extreme expressiveness of the mouth is due in part to its flexibility and wide range of movement. This range is attributable to the muscular structure that controls the lips under the surface, a complex web of facial muscles that are so interconnected with one another and with the different facial features that if you were to wiggle your nose, your upper lip would move from side to side as well.
The main muscle of the mouth is the orbicularis oris. The orbicularis oris forms the muzzle by surrounding the orifice of the mouth with several different layers of muscle fiber and extends from the base of the nose down to the top of the chin. The buccinator works with the orbicularis oris, stretching the circular fibers around the mouth’s cavity. It is used when compressing the lips and cheeks against the teeth. The buccinator starts at the mandible (jawbone) and moves deeper than the rest of the facial muscles to connect to the modiolus and the upper and lower lips. Laterally flanking each angle of the mouth, the modioli act as the anchors for many facial muscles. These muscles are held together by fibrous tissue and are extremely important for facial expression.
The fibers of the orbicularis oris have origins in other facial muscles that end and join with the lips’ own muscle fibers. Specifically, the three muscles that lead into the upper lip are the levator labii superioris, the levator labii superioris alaeque nasi, and the zygomaticus minor. These three muscles control the upper lip region and move the lips sideways and raise them. They are well connected to the nose, too, and are helpful for wiggling the nose as well as expressing emotions of grief and contempt. The nearby levator labii superioris originates at the maxilla. The muscle that flanks the mouth on both sides and is in control of raising the lip high and sideways is the zygomaticus major. The lower lip and mouth is controlled primarily by three muscles: the risorius, the triangularis (or depressor anguli oris), and the mentalis. These muscles are used to pull down the corners of the mouth and lower lip. The mentalis can even wrinkle the chin.
Another important muscle is the masseter, which starts at the zygomatic arch (cheekbone) and stretches down to the ramus of the mandible. This muscle controls the opening and closing of the mouth as well as the pushing out of the chin; it is used to express anger and emotional tension.
The lips are one of the face’s most prominent and expressive features. They help to visually communicate our emotions, and they have many functions, including helping us to eat and articulate speech and—most important—to kiss and be intimate. It takes careful attention and observation to evaluate each subject’s own unique turns, tucks, folds, and roundness of the mouth and lips. But the time and patience is well worth it; with this pragmatic and well-observed structure in place, you can infuse your subject with an emotive strength.
To see the Table of Contents for the Winter 2009 issue of Drawing magazine, click here.