Orbicularis oris

Orbicularis oris is a complex of muscles in the lips that encircles the mouth. Until recently, it was misinterpreted as a sphincter, or circular muscle, but it is actually composed of four independent quadrants that interlace and give only an appearance of circularity.

It is also referred to as the kissing muscle because it is used to pucker the lips. The muscle is also used extensively in speech. The orbicularis oris muscle is not a simple sphincter muscle like the orbicularis oculi that encircles the eye. Instead, it consists of numerous strata of muscle fibers surrounding the mouth like the layers of an onion, and it has various zones that can be independently activated.

Structure

The orbicularis oris muscle is a complex of muscles that encircles the mouth. It is composed of numerous strata of muscle fibers that surround the mouth like the layers of an onion. The muscle is not a simple sphincter muscle like the orbicularis oculi that encircles the eye. Instead, it has various zones that can be independently activated.

Function

The orbicularis oris muscle is used to close the mouth and to pucker the lips, such as when kissing or whistling. It is also used extensively in the articulation of speech. The muscle is also used in facial expressions, and it can be voluntarily controlled.

Clinical significance

The orbicularis oris muscle can be affected in conditions such as Bell's palsy, which is a paralysis of the facial muscles. This can result in an inability to close the mouth, leading to drooling. Other conditions that can affect the orbicularis oris muscle include Parkinson's disease and stroke.

See also

• Facial muscles
• Facial expressions
• Bell's palsy
• Parkinson's disease
• Stroke

References

Orbicularis oris Resources
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