Boundaries and fascial layers
The topography of the buccal region is clearly delineated by neighboring anatomical landmarks. Superiorly, the area is bounded by the zygomatic arch, and inferiorly by the lower margin of the mandible. The inner (medial) boundary runs along natural facial lines: the nasolabial and nasomaxillary folds. Externally (laterally), the region reaches the anterior border of the masseter muscle (m. masseter).
Tissues here are arranged in a strict sequence, forming seven distinct layers:
- Skin. Characterized by a small thickness, containing a large number of sebaceous and sweat glands.
- Subcutaneous adipose tissue. Abundantly developed and very tightly fused with the skin.
- Superficial fascia. Its leaves split, forming protective fascial sheaths for most of the facial muscles of expression.
- Layer of facial expression muscles. The musculature lies in several tiers. The lower part of the orbicularis oculi muscle (m. orbicularis oculi) runs superficially. Hidden beneath it are the zygomaticus minor and major muscles (mm. zygomatici minor et major). At the deepest level of this layer is the levator labii superioris muscle (m. levator labii superioris).
- Deep fascia (proper fascia). Represented by two leaves that envelop the specific fat accumulation of this zone.
- Deep (buccopharyngeal) fascia. Creates isolating sheaths for the pharynx and the deepest facial muscle — the buccinator.
- Buccinator muscle. Completes the tissue mass of the region, separating it from the mucous membrane of the oral vestibule.
Buccal fat pad (Bichat's fat pad)
The buccal fat pad (corpus adiposum buccae) is a localized accumulation of brown adipose tissue. Its main physiological task is to optimize the sucking mechanism in infants during breastfeeding. As a person grows older, the volume of brown fat significantly decreases, gradually being replaced by connective tissue elements.
Anatomically, this pad lies deep in the buccal region, directly adjacent to the anterior border of the masseter muscle. The fat pad is reliably isolated from the surrounding tissues, muscles, and subcutaneous tissue by a dense connective tissue capsule.
A critical topographic feature is the processes of the fat pad, which extend far beyond the cheek:
- Temporal process: extends upward under the zygomatic bone, runs along the outer wall of the orbit, and reaches the temporal fossa.
- Orbital process: localized in the infratemporal fossa, closely adhering to the inferior orbital fissure.
- Pterygopalatine process: passes through the space bounded by the inferior orbital fissure superiorly, the jawbones anteriorly, and the base of the pterygoid process of the sphenoid bone posteriorly. In some cases, this process is capable of penetrating the cranial cavity through the inferomedial part of the superior orbital fissure, reaching the wall of the cavernous sinus.
Anatomy of the buccinator muscle
The buccinator muscle (m. buccinator) forms the muscular foundation of the region under consideration. It originates from the alveolar processes of both jaws and a specific tendinous band — the pterygomandibular raphe (raphe pterygomandibularis). Extending anteriorly, the fibers of the buccinator muscle weave into the structure of the orbicularis oris muscle.
On the outer side, the muscle is tightly covered by the buccopharyngeal fascia (fascia buccopharyngea), and on the inner side, it is lined with the oral mucosa. An important topographic landmark is that the parotid duct pierces the buccinator muscle strictly at the level of the upper first molars.
Important neurovascular and lymphatic structures are located on the outer surface of the muscle: the buccal nerve (n. buccalis, a branch of the trigeminal nerve), nourishing vessels, and a group of facial lymph nodes (buccal, nasolabial, molar).
Clinical significance of the region
The surgical anatomy of the buccal region is of critical importance in maxillofacial surgery due to the pathways of spread of purulent infections. Despite its dense capsule, the buccal fat pad acts as an excellent conductor for inflammatory processes, which most commonly have a primary odontogenic origin (from the teeth).
Via the processes of the fat pad, infection can easily migrate into the temporal and infratemporal regions, as well as into the orbit. The pterygopalatine process poses a particular danger. It is its deep location that explains the paradoxical mechanism by which a severe facial phlegmon can spread to the cavernous sinus of the brain via a direct tissue pathway — even without involving facial venous anastomoses.
Briefly: answers to topical questions
Which muscles of facial expression are located in the buccal region?
In the buccal region, muscles of facial expression are arranged in several layers. These include:
- Orbicularis oculi muscle (m. orbicularis oculi) — represented by its lower part, lies superficially.
- Zygomaticus minor and major muscles (mm. zygomatici minor et major) — located beneath the orbicularis oculi muscle.
- Levator labii superioris muscle (m. levator labii superioris) — located deeper, covered by the zygomatic muscles.
- Risorius muscle and levator anguli oris muscle — partially represented in this region.
- Buccinator muscle (m. buccinator) — the deepest facial muscle of the region.
Which nerves provide motor and sensory innervation to the buccal region?
Innervation of the buccal region is provided by branches of the trigeminal (sensory) and facial (motor) nerves.
Sensory innervation:
- Buccal nerve (n. buccalis) — a branch of the mandibular nerve, innervates the skin and mucous membrane of the cheek.
- Infraorbital nerve (n. infraorbitalis) — a branch of the maxillary nerve, innervates the anterior parts of the cheek.
Motor innervation:
- Facial nerve (n. facialis) — its buccal branches (rr. buccales) run toward the midpoint between the ala of the nose and the angle of the mouth, innervating the muscles of facial expression.
Which arteries and veins provide blood supply to the buccal region?
Blood supply to the buccal region is provided by the facial and transverse facial artery systems, and venous outflow occurs via veins of the same name.
Arterial bed:
- Facial artery (a. facialis) — its initial segment runs in the subcutaneous adipose tissue of the buccal region, the vessel is highly tortuous.
- Transverse facial artery (a. transversa faciei) — runs transversely along the outer surface of the masseter muscle.
- Buccal artery (a. buccalis) — participates in the blood supply to the cheeks.
Venous outflow:
- Facial vein (v. facialis) — the main venous collector of the face.
- Transverse facial vein (v. transversa faciei) — accompanies the artery of the same name and is a tributary of the facial vein.
For quick memorization of the three processes of the buccal fat pad, use the short mnemonic «T-O-P»: Temporal, Orbital, Pterygopalatine.
Class and exam questions
Where exactly does the parotid duct run?
The duct pierces the thickness of the buccinator muscle (m. buccinator) strictly at the level of the upper first molars.
How can purulent infection from the face spread to the cranial cavity without the involvement of veins?
Infection can spread directly through the pterygopalatine process of the buccal fat pad, which in some cases penetrates into the cranial cavity up to the cavernous sinus.
Which facial muscle lies deepest in the buccal region?
The deepest muscle is the buccinator muscle (m. buccinator), which lies within its own sheath formed by the buccopharyngeal fascia.
What else to study on this topic
- Topography of the buccal nerve and its branches
- Arterial blood supply and venous outflow of the buccal region
- Anatomy of the facial lymph nodes
- Structure and topography of the pterygomandibular raphe
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