Main muscles surrounding the oral fissure
The central element of the muscular apparatus in this region is the orbicularis oris muscle (m. orbicularis oris). Its anatomical function is the tight closure of the lips. With isolated and forceful contraction, this muscle is able to protrude the lips forward, forming a specific "pucker".
The lateral wall of the oral cavity is formed by the buccinator muscle (m. buccinator). Its main function is to press the cheek tightly against the dental arches, which prevents biting of the mucosa and helps move food during chewing. From a clinical perspective, it is extremely important to remember an anatomical feature: the parotid duct (ductus parotideus) runs directly through the thickness of this muscle's fibers.
Elevators: muscles elevating the lip and angle of the mouth
An extensive group of muscles is located above the oral fissure and is responsible for elevating the upper lip and pulling the angle of the mouth upward, which physiologically enables smiling. This complex includes:
- Levator labii superioris alaeque nasi muscle (m. levator labii superioris alaeque nasi).
- Levator labii superioris muscle (m. levator labii superioris).
- Levator anguli oris muscle (m. levator anguli oris).
- Zygomaticus major and minor muscles (m. zygomaticus major and m. zygomaticus minor).
Additionally, the risorius muscle (m. risorius) is distinguished in this zone, which upon contraction pulls the angle of the mouth strictly in a lateral direction.
Depressors and mentalis muscle
Below the oral fissure lie the antagonist muscles that pull the oral structures downward. Depressor anguli oris (m. depressor anguli oris) and depressor labii inferioris (m. depressor labii inferioris) pull the respective structures downward.
Special attention should be paid to the mentalis muscle (m. mentalis). Unlike the depressors, upon contraction it pushes the lower lip anteriorly and superiorly, forming a characteristic dimple on the chin skin.
Blood supply and innervation
The facial muscles of the mouth are characterized by rich vascularization and complex neural regulation.
Innervation of all described muscles is carried out 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 provided by a developed arterial network. The main 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 mandible
Important fascial spaces are located in the immediate vicinity of the oral cavity, knowledge of which is critically necessary in maxillofacial surgery.
The submandibular space is localized around the salivary gland of the same name. Its main anatomical characteristic is the presence of direct communications with the cellular tissue of the floor of the mouth and the fascial spaces of the neck. It is through these pathways that rapid spread of dangerous "odontogenic" phlegmons (suppurative processes originating from affected teeth) occurs.
The submental space is located between the anterior bellies of the digastric muscle (m. digastricus) and the body of the hyoid bone. Lymph nodes reside within this cellular tissue, and the space itself freely communicates with the analogous region on the opposite side of the neck.
Briefly: answers to topical questions
What anatomical structures bound the submental fascial space?
The submental fascial space is bounded by the muscles, fasciae, and bony structures of the neck.
- Superior boundary — the mylohyoid muscle, covered inferiorly by the deep layer of the deep cervical fascia.
- Lateral boundaries — the anterior bellies of the digastric muscle (m. digastricus).
- Inferior boundary — the superficial cervical fascia.
- Posterior boundary — the body of the hyoid bone.
Where does the buccinator muscle originate and insert?
The buccinator muscle (m. buccinator) originates from the bony structures of the jaws and 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.
To which lymph nodes does lymphatic drainage from the lips and cheeks occur?
Lymphatic drainage from the lips and cheek region is associated with 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 and lead 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.
To memorize the innervation of the oral region, remember the branches of n. facialis by their projection: cheekbones — zygomatici, cheeks — buccales, lower jaw margin — marginalis mandibulae.
Class and exam questions
Which muscle is pierced by the parotid duct?
The parotid duct (ductus parotideus) passes through the thickness 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 with blood by the superior and inferior labial arteries (branches of a. facialis), as well as the infraorbital and mental arteries.
What is the clinical danger of the submandibular fascial space?
It has a direct communication with the cellular tissue of the floor of the mouth and the spaces of the neck. This creates ideal conditions for the spread of severe odontogenic phlegmons.
What else to study on this topic
- Topography of the facial nerve branches (n. facialis)
- Branching of the facial artery (a. facialis) on the face
- Anatomy of the buccinator muscle and the course of the parotid duct
- Connection of the submandibular space with the cervical fasciae
- Pathways of spread of odontogenic phlegmons
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