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Facial Muscles of the Mouth

Musculi faciales

For medical students2 min readUpdated 2026-10-10

The facial muscles of the mouth are a specialized group of muscle fibers surrounding the oral fissure that control the complex movements of the lips and cheeks. These muscles allow for articulation, retention of food during mastication, and a wide range of facial expressions.

Oral sphincterThe orbicularis oris (*m. orbicularis oris*) acts as the primary sphincter of the oral fissure.
Key clinical relationThe parotid duct pierces the buccinator muscle (*m. buccinator*).
Blood supplySupplied by branches of the facial, infraorbital, mental, and buccal arteries.
InnervationMotor innervation is provided by branches of the facial nerve (*n. facialis*).

Primary Muscles Surrounding the Oral Fissure

The central element of the muscular apparatus in this region is the orbicularis oris (m. orbicularis oris). Its anatomical function is to tightly close the lips. When isolated and strongly contracted, this muscle protrudes the lips forward, forming a pursed shape.

The lateral wall of the oral cavity is formed by the buccinator muscle (m. buccinator). Its primary task is to tightly press the cheek against the dental arches, which prevents biting the oral mucosa and aids in food manipulation during chewing. From a clinical perspective, it is crucial to remember this key anatomical feature: the parotid duct (ductus parotideus) runs directly through the substance of this muscle.

Elevators: Muscles Elevating the Lip and Angle of the Mouth

A broad group of muscles lies superior to the oral fissure, responsible for elevating the upper lip and pulling the angle of the mouth superiorly, which physiologically enables smiling. This complex includes:

Additionally, the risorius muscle (m. risorius) is located in this zone, which pulls the angle of the mouth strictly in a lateral direction upon contraction.

Depressors and the Mentalis Muscle

Inferior to the oral fissure lie the antagonistic muscles that pull the oral structures downward. The depressor anguli oris (m. depressor anguli oris) and depressor labii inferioris (m. depressor labii inferioris) pull their respective structures inferiorly.

Special attention should be given to the mentalis muscle (m. mentalis). Unlike the depressors, its contraction pushes the lower lip anteriorly and superiorly while forming the characteristic dimple on the skin of the chin.

Blood Supply and Innervation

The facial musculature of the mouth features a rich vascular network and complex neural regulation.

Innervation of all described muscles is provided exclusively by motor fibers of the facial nerve (n. facialis). Its buccal branches (rami buccales), zygomatic branches (rami zygomatici), and marginal mandibular branch (ramus marginalis mandibulae) are distributed in the oral region.

Blood supply is ensured by a well-developed arterial network. The primary source is the facial artery (a. facialis), which gives off the superior and inferior labial arteries (a. labialis superior, a. labialis inferior), as well as the angular artery (a. angularis). Additional blood inflow comes from the infraorbital (a. infraorbitalis), mental (a. mentalis), and buccal (a. buccalis) arteries.

Fascial Spaces of the Lower Jaw

Important fascial spaces are located in the immediate vicinity of the oral cavity, knowledge of which is critical in maxillofacial surgery.

Submandibular space is localized around the submandibular salivary gland of the same name. Its main anatomical feature is direct communication with the fascial spaces of the floor of the mouth and the neck. These pathways facilitate the rapid spread of dangerous odontogenic phlegmons (suppurative processes originating from diseased teeth).

Submental space lies between the anterior bellies of the digastric muscle (m. digastricus) and the body of the hyoid bone. Lymph nodes reside within this connective tissue, and the space freely communicates with the corresponding area on the contralateral side of the neck.

Mnemonic

To remember the innervation of the oral region, associate the branches of the n. facialis with their projections: cheekbones — zygomatici, cheeks — buccales, lower jaw margin — marginalis mandibulae.

Frequently asked questions

What anatomical structures bound the submental fascial space?

The submental space is bounded by the muscles, fasciae, and bony structures of the neck.

  • Superior boundary — mylohyoid muscle, covered inferiorly by the deep layer of the deep cervical fascia.
  • Lateral boundaries — anterior bellies of the digastric muscle (m. digastricus).
  • Inferior boundary — superficial layer of the cervical fascia.
  • Posterior boundary — body of the hyoid bone.
Where does the buccinator muscle originate and insert?

The buccinator muscle (m. buccinator) originates from the bone structures of the jaws and a connective tissue raphe, and inserts into the muscles of the mouth.

  • Origin — alveolar processes of both jaws and the pterygomandibular raphe (raphe pterygomandibularis).
  • Insertion — blends anteriorly into the orbicularis oris muscle.
Into which lymph nodes does lymph drainage from the lips and cheeks occur?

Lymph drainage from the lips and cheek region involves the following groups of lymph nodes:

  • Submandibular lymph nodes (nodi lymphatici submandibulares) — lymphatic vessels of the upper lip and the lateral third of the lower lip accompany the facial artery to these nodes; they also receive lymph from the buccal and mandibular nodes.
  • Submental lymph nodes (nodi lymphatici submentales) — receive lymph from the middle third of the lower lip.
  • Mandibular lymph nodes — collect lymph from the upper and lower lips.
  • Facial lymph nodes (nodi lymphoidei faciales) — located along the facial artery and its branches; these include the buccal (nodus buccinatorius), nasolabial (nodus nasolabialis),malar, and mandibular nodes.
Which muscle is pierced by the parotid duct?

The parotid duct (ductus parotideus) passes through the substance of the buccinator muscle (m. buccinator) before opening into the vestibule of the mouth.

Which arteries participate in the blood supply to the lips?

The lips are supplied by the superior and inferior labial arteries (branches of the a. facialis), as well as the infraorbital and mental arteries.

Why is the submandibular fascial space clinically dangerous?

It has direct communication with the fascial spaces of the floor of the mouth and neck, creating ideal conditions for the spread of severe odontogenic infections.

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