Muscles surrounding the orifice of the mouth

There are several well-defined muscles around the mouth opening. These muscles include the circular muscle of the mouth, the muscle that lowers the corner of the mouth, the muscle that lowers the lower lip, the chin and the buccal muscles, the muscle that lifts the upper lip, the small and large zygomatic muscles, the muscle that raises the corner of the mouth, and the muscle of laughter.

The circular muscle of the mouth (m.orbicularis oris) forms the muscular basis of the upper and lower lips. This muscle consists of the marginal and labial parts, the bundles of which have not the same orientation.

The marginal part (pars marginalis) is a peripheral, wider muscle department. This part is formed by muscle bundles that approach the upper and lower lips from the other, proximal to the oral opening of facial muscles. The marginal part is formed by bundles of the buccal muscle; muscle that lifts the upper lip; muscle lifting the corner of the mouth; muscle, lowering the lower lip; muscle, lowering the corner of the mouth, and others.

The labialis part (pars labialis) lies in the thickness of the upper and lower lips. The bundles of muscle fibers extend from one corner of the mouth to the other.

Both parts (marginal and labial) of the upper and lower lips are intertwined in the skin and mucous membrane, and also connect with each other in the region of the corners of the mouth and pass from the lower lip to the upper and vice versa.

Function: the circular muscle of the mouth narrows, closes the mouth slit, participates in the act of sucking and chewing.

Innervation: facial nerve (VII).

Blood supply: upper and lower labial and chin arteries.

The muscle that lowers the corner of the mouth (m.depressor anguli oris) begins on the base of the lower jaw, between the chin and the level of the first small molar. The fibers of this muscle, converging, go up and attach to the skin of the corner of the mouth. At the place of the beginning of the muscle, lowering the angle of the mouth, part of its bundles intertwined with bundles of the subcutaneous muscle of the neck.

Function: pulls the corner of the mouth down and laterally.

Innervation: facial nerve (VII).

Blood supply: lower labial and chin arteries.

Blood supply: lower labial and chin arteries.

The muscle that lowers the lower lip (m.depressor labii inferioris) begins on the base of the lower jaw, below the chin opening. Partially covered with a muscle that lowers the corner of the mouth. The bunches of the muscle, lowering the lower lip, pass upward and medially and attach to the skin and mucosa of the lower lip.

Function: pulls the lower lip down and somewhat laterally, acting together with the same-named muscle of the opposite side, can turn the lip outward; participates in the formation of an expression of irony, sadness, disgust.

Innervation: facial nerve (VII).

Blood supply: lower labial and chin arteries.

The chin muscle (m.mentalis) is represented by a cone-shaped bundle of muscle fibers that begin on the alveolar elevations of the lateral and medial incisors of the lower jaw, pass down and medially, connect to the fibers of the same-named muscle of the opposite side and attach to the skin of the chin.

Function: pulls upward and laterally the chin's skin (dimples appear on the skin); promotes protrusion of the lower lip forward.

Innervation: facial nerve (VII).

Blood supply: lower labial and chin arteries.

The cheek muscle (m.buccinator) is thin, quadrangular in shape, forming the muscular base of the cheek. Begins on an oblique line on the branch of the lower jaw and the outer surface of the alveolar arch of the upper jaw at the level of the large molars, and also on the anterior margin of the wing-mandibular suture that passes between the lower jaw and the pterygoid crochet. Bunches of muscle are directed to the corner of the mouth, partially crossed and continue into the thickness of the muscular base of the upper and lower lips. At the level of the upper large molar tooth, the muscle permeates the parotid duct (parotid duct of the parotid gland).

Function: pulls the corner of the mouth back; presses his cheek to his teeth.

Innervation: facial nerve (VII).

Blood supply: buccal artery.

The muscle that lifts the upper lip (m. Levator labii superioris) begins on the entire infraorbital margin of the upper jaw. Bunches of muscle converge downwards and are weaved into the thickness of the corner of the mouth and into the wing of the nose.

Function: lifts the upper lip; participates in the formation of nasolabial sulcus, extending from the lateral side of the nose to the upper lip; pulls the wing of the nose up.

Innervation: facial nerve (VII).

Blood supply: infraorbital and upper labial arteries.

The small zygomatic muscle (m.zygomaticus minor) begins on the malar bone at the lateral margin of the muscle, lifting the upper lip. Bunches of small zygomatic muscles pass downward medially and are weaved into the skin of the corner of the mouth.

Function: raises the angle of the mouth.

Innervation: facial nerve (VII).

Blood supply: infraorbital and buccal arteries.

The large zygomatic muscle (m.zygomaticus major) begins on the malar bone, is attached to the corner of the mouth.

Function: pulls the corner of the mouth outward and upwards, is the main muscle of laughter.

Innervation: facial nerve (VII).

Blood supply: infraorbital and buccal arteries.

The muscle that lifts the corner of the mouth (m.levator anguli oris) begins on the anterior surface of the maxilla in the canine fossa region; is attached to the corner of the mouth.

Function: pulls the angle of the upper lip upwards and laterally.

Innervation: facial nerve (VII).

Blood supply: infraorbital artery.

The muscle of laughter (m.risorius) begins on the chewing fascia, is directed forward and medially, attached to the skin of the corner of the mouth. Usually mild, often absent.

Function: pulls the corner of the mouth laterally, forms a dimple on the cheek.

Innervation: facial nerve (VII).

Blood supply: facial artery, transverse artery of the neck.

[1], [2], [3], [4], [5]