Orbicularis oris muscle
Encyclopedia
In human anatomy
, the orbicularis oris muscle is the sphincter
muscle around the mouth
.
"Orbicularis Oris is a complex of muscles in the lips that encircle 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 one of the muscle
s used in the playing of all brass instrument
s and some woodwind instrument
s.
This muscle closes the mouth and puckers the lips when it contracts.
It consists partly of fibers derived from the other facial muscles which are inserted into the lips, and partly of fibers proper to the lips.
Of the former, a considerable number are derived from the Buccinator
and form the deeper stratum of the Orbicularis.
Some of the Buccinator fibers—namely, those near the middle of the muscle—decussate at the angle of the mouth, those arising from the maxilla passing to the lower lip, and those from the mandible to the upper lip.
The uppermost and lowermost fibers of the Buccinator pass across the lips from side to side without decussation.
Superficial to this stratum is a second, formed on either side by the Caninus and Triangularis, which cross each other at the angle of the mouth; those from the Caninus passing to the lower lip, and those from the Triangularis to the upper lip, along which they run, to be inserted into the skin near the median line.
In addition to these there are fibers from the Quadratus labii superioris, the Zygomaticus, and the Quadratus labii inferioris; these intermingle with the transverse fibers above described, and have principally an oblique direction.
The proper fibers of the lips are oblique, and pass from the under surface of the skin to the mucous membrane, through the thickness of the lip.
Finally, there are fibers by which the muscle is connected with the maxillæ and the septum of the nose above and with the mandible below.
In the upper lip these consist of two bands, lateral and medial, on either side of the middle line; the lateral band m. incisivus labii superioris arises from the alveolar border of the maxilla, opposite the lateral incisor tooth, and arching lateralward is continuous with the other muscles at the angle of the mouth; the medial band m. nasolabialis connects the upper lip to the back of the septum of the nose.
The interval between the two medial bands corresponds with the depression, called the philtrum, seen on the lip beneath the septum of the nose.
The additional fibers for the lower lip constitute a slip m. incisivus labii inferioris on either side of the middle line; this arises from the mandible, lateral to the Mentalis, and intermingles with the other muscles at the angle of the mouth.
Human anatomy
Human anatomy is primarily the scientific study of the morphology of the human body. Anatomy is subdivided into gross anatomy and microscopic anatomy. Gross anatomy is the study of anatomical structures that can be seen by the naked eye...
, the orbicularis oris muscle is the sphincter
Sphincter
A sphincter is an anatomical structure, or a circular muscle, that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning...
muscle around the mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
.
"Orbicularis Oris is a complex of muscles in the lips that encircle 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 one of the muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s used in the playing of all brass instrument
Brass instrument
A brass instrument is a musical instrument whose sound is produced by sympathetic vibration of air in a tubular resonator in sympathy with the vibration of the player's lips...
s and some woodwind instrument
Woodwind instrument
A woodwind instrument is a musical instrument which produces sound when the player blows air against a sharp edge or through a reed, causing the air within its resonator to vibrate...
s.
This muscle closes the mouth and puckers the lips when it contracts.
Anatomy
The Orbicularis oris is not a simple sphincter muscle like the Orbicularis oculi; it consists of numerous strata of muscular fibers surrounding the orifice of the mouth but having different direction.It consists partly of fibers derived from the other facial muscles which are inserted into the lips, and partly of fibers proper to the lips.
Of the former, a considerable number are derived from the Buccinator
Buccinator
The buccinator muscle is a muscle at the side of the face.Buccinator may also refer to:* Buccinator artery * Buccinator lymph node* Buccinator nerve * An ancient Roman buccina player...
and form the deeper stratum of the Orbicularis.
Some of the Buccinator fibers—namely, those near the middle of the muscle—decussate at the angle of the mouth, those arising from the maxilla passing to the lower lip, and those from the mandible to the upper lip.
The uppermost and lowermost fibers of the Buccinator pass across the lips from side to side without decussation.
Superficial to this stratum is a second, formed on either side by the Caninus and Triangularis, which cross each other at the angle of the mouth; those from the Caninus passing to the lower lip, and those from the Triangularis to the upper lip, along which they run, to be inserted into the skin near the median line.
In addition to these there are fibers from the Quadratus labii superioris, the Zygomaticus, and the Quadratus labii inferioris; these intermingle with the transverse fibers above described, and have principally an oblique direction.
The proper fibers of the lips are oblique, and pass from the under surface of the skin to the mucous membrane, through the thickness of the lip.
Finally, there are fibers by which the muscle is connected with the maxillæ and the septum of the nose above and with the mandible below.
In the upper lip these consist of two bands, lateral and medial, on either side of the middle line; the lateral band m. incisivus labii superioris arises from the alveolar border of the maxilla, opposite the lateral incisor tooth, and arching lateralward is continuous with the other muscles at the angle of the mouth; the medial band m. nasolabialis connects the upper lip to the back of the septum of the nose.
The interval between the two medial bands corresponds with the depression, called the philtrum, seen on the lip beneath the septum of the nose.
The additional fibers for the lower lip constitute a slip m. incisivus labii inferioris on either side of the middle line; this arises from the mandible, lateral to the Mentalis, and intermingles with the other muscles at the angle of the mouth.
Clinical significance
Newborn babies are occasionally born without one or both sides of this particular muscle resulting in a slight droop to the affected side of the face.External links
- Facial Muscles - BBC Picture of the circular-shaped muscle
- Facial Muscles - BBC (Flash) Animation of movements of the muscle