LIPS

He was a person of very striking aspect, with a white, lofty, and impending brow, large, brown, melancholy eyes, and a mouth which, unless when he forcibly compressed it, was apt to be tremulous, expressing both nervous sensibility and a vast power of self-restraint. --Nathaniel Hawthorne (The Scarlet Letter)

Mood signals. 1. The muscular, fleshy, hairless folds surrounding the mouth opening, which may be moved a. to express emotions, b. to pronounce words, and c. to kiss. 2. The most emotionally expressive parts of the human body.

Usage: Lips give off telling cues about inner feelings and moods. So connected are lips a. to our visceral nervous system and b. to companion muscles of our lower face, that we rarely keep them still. Like hands, lips are incredibly gifted communicators which always bear watching.

Anatomy I. Lip size (full or thin), curvature (sinuous or straight), and eversion (everted or inverted) vary in men and women, and in geographic populations as well. The principal lip muscle, orbicularis oris, is a sphincter consisting a. of pars marginalis (beneath the margin of the lips themselves), and b. pars peripheralis (around the lips' periphery from the nostril bulbs to the chin). (N.B.: P. marginalis is uniquely developed in humans for speech.) Contraction of orbicularis oris tenses the lips and reduces their eversion.

Anatomy II. Lips may be moved directly by orbicularis oris and by direct labial tractor muscles in the upper and lower lips. Contraction of levator labii superioris alaeque nasi, levator labii superioris, and/or zygomaticus minor, e.g., elevate and/or evert the upper lip; while depressor labii inferioris and/or platysma par labialis depress and/or evert the lower lip. The complexity of muscle interactions thus reflects the complexity of emotion blends.

Anatomy III. Lips may also be moved indirectly by nine (or more) other facial muscles (e.g., by zygomaticus major in laughing) through attachments to a fibromuscular mass known as the modiolus. That so many facial muscles interlink via the modiolus makes our lips extremely expressive of attitudes, opinions, and moods.

Human lips encode a number of distinctive visual features that have been migrated to the auditory channel. Among these visible features are the human lips' reddish--"vermillion"--coloration.

Microanatomy of lips. Along with brows, eyes, and nose, lips are among the most noticeable landmarks of the human face. Lips attract visual attention through their color, shape, movement, and linear detail. The reddish, vermilion hue shows because lip tissue is thinner than surrounding epidermal tissue, allowing its dense network of blood vessels to show through. Meanwhile, a subtle "white roll" surrounds the superior and inferior borders of the lips, between pars marginalis and pars peripherals muscles. As the human visual sense is highly stimulated by linear detail, this barely noticeable, usually pale but often darker, borderline helps to frame the lips, bringing further notice to their gestalt, sinuous shape.

White lip roll. In the Canadian Journal of Plastic Surgery, Geethan Chandran and Donald Lalonde write: "The lip roll resides at the lip vermilion/cutaneous junction. Although some call it the 'white roll', it is not white in dark-skinned individuals; therefore, we prefer the term 'lip roll'. It is a three-dimensional, hill-like structure with adnexal structures of specialized glands and fat underlying the surrounding tissue that imparts a roll to the lip. One of the most important aspects of obtaining a good result when reconstructing a lip roll is that it heals with a solid three-dimensional hill, bump or roll effect across the scar. If the hill is effaced across the scar, it can be visible across a room to the casual observer. If the three-dimensional roll is maintained across the scar, the lip appears aesthetically pleasing (Video: go to www.pulsus.com)" (Chandran & Lalonde 2013; emphasis added).

Sinuous shape.. At rest, human lips generally evert outward, except when tightened into the compressed-lips display (see below, Lip-compression). The upper lip has a curvilinear shape--which, in English phraseology, is called "Cupid's bow"--perhaps a reflection of its role in kissing. The fleshy indentation below the nostrils, known as the philtrum, adds extra stretchable tissue to allow room for wide-open lip expressions. Meanwhile, in tandem with the upper lip's sinuous, recurved-bow shape, the lower lip's generally greater eversion and expressive, crescent-Moon shape in speech, makes human lips worthy of close visual inspection.

Neuro-aesthetics. Indeed, watching lips may be emotionally pleasing as it stimulates pleasure centers of the brain. That lips matter greatly to the brain was confirmed in the classic eye-motion research by Soviet psychologist Alfred L. Yarbus (1914-1986). According to Nicholas Wade and Galina I. Rozhkova: "One of the enduring features of Yarbus's investigations is the pattern of eye movements when viewing faces (or, more accurately, pictures of faces). His record of eye movements over the magazine picture of Girl from the Volga . . ." has been widely reproduced in textbooks. "Yarbus wrote: 'When looking at a human face, an observer usually pays most attention to the eyes, the lips, and the nose. The other parts of the face are given much more cursory consideration' " (Wade & Rozhkova 2017; https://yarbus.eu/faces/ [accessed Aug.15, 2023]).

Embryology. On day 22, pharyngeal arches form, and by 20 weeks, orbicularis oris (and other muscles of expression) form from the 2nd pharyngeal arch.

Infancy. From 3-to-6 months, babies bring objects to their lips to be explored, and make sounds with objects placed against their lips.

Lipreading. Functional magnetic resonance imaging (fMRI) studies show that the linguistic visual cues afforded by lip movements activate areas of auditory cortex in normal hearing individuals (Calvert et al. 1997).

Observation. Unconscious tension in lips reflects how we truly feel about, e.g., a boss's work assignment, a friend's off-hand comment, or a colleague's "helpful" idea. A slight drooping at the mouth corners (through unconscious contraction of depressor anguli oris) may be the first visible sign of (unvoiced) sadness or disappointment.

Primatology. Beginning with muscular contractions for suckling breast milk, the primate brain added the ability to grasp food items with everted lips. Chimps, e.g., use prehensile lips to pluck termites from twigs. (N.B.: Humans use their own prehensile lips to pluck french fries from a bag.)

Neuro-notes I. The facial nerve's (i.e., cranial VII's) lower nucleus controls the pouted-, curled-, and tightened-lip expressions we unintentionally use to reveal our moods. Instructions for these signals come from limbic modules, such as the amygdala and cingulate gyrus, by way of the brain stem. Because there is little or no conscious control from higher brain centers, lip movements provide trustworthy cues.

Neuro-notes II. Our brain devotes an unusually large part of its surface area to lips (see HOMUNCULUS). In the mind's eye, as a result a. of the generous space they occupy on the sensory and motor strips of our neocortex, and b. of the older paleocircuits linking them to emotional, feeding, and grooming centers of the mammalian brain, almost anything a lip does holds potential as a sign.

Neuro-notes III. Our human brain added precision to lip movements through nerve fibers linked to the primary motor neocortex. Today, fiber links from this area descend through the corticobulbar tract to motor neurons of the facial nerve, whose branches take charge of specific muscle fibers of the lips. That we can whistle a tune (and that whistle languages are "spoken" in some areas of the world) testifies to our lips' extremely high IQ as neurological smart parts.

See also DISGUST, LIP-COMPRESSION, LIP-POUT, LIP-PURSE, SELF-TOUCH, TENSE-MOUTH.

Copyright 1999 - 2024 (David B. Givens/Center for Nonverbal Studies)
Detail of a male human's face, showing the muscular, fleshy, hairless lips (photo credit: unknown)