Superficial regions of the face
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The foundations of the facial part of the head are the bones of the splanchnocranium.
Orbital region:
The boundaries correspond to the extent of orbicularis oculi muscle. The main features of the region are the eyelids, palpebrae, which close the entrance to the orbit. The upper eyelid is wider and semilunar, and therefore covers a larger portion of the cornea than the sickle-shaped lower eyelid. At the medial corner are found the components of efferent lacrimal pathways: the lacrimal caruncle, the lacrimal puncta, and the lacrimal sac.
The skin of the eyelids stretches easily and is often pigmented. The upper eyelid is innervated from 1st branch of trigeminal nerve, the lower eyelid from the 2nd branch.
Subcutaneous tissue contains loose connective tissue without fat. In the subcutaneous tissue of the free edges of both eyelids run fine arterial arcades, the superior and inferior palpebral arches. From the medial side run small branches of the superior and inferior medial palpebral arteries, and both branches of the ophthalmic artery. Further contribution comes from the terminal branch of the angular artery, and the branch of the facial artery. Lateral contributions come from the branches of the superior and inferior lateral palpebral artery, from the lacrimal artery, and the branches of zygomaticofacial and transverse facial arteries. Along the perimeter of the orbit anastomoses are further developed among the supraorbital artery, the supratrochlear artery, and the superficial temporal artery, completing the complex of fine peripheral anastomoses between external and internal carotid arteries. Venous blood drains into the veins of both orbits as well as to the facial vein.
The muscular substrate of the eyelids is the orbicular oculi muscle, circularly spread on the anterior surface of both tarsal plates and the orbital septum. its outer orbital part extends all around the edge of orbit. The next layer is the tarsal disc, and the last layer of the eyelid is the conjunctiva, specifically its palpebral part. Laterally under the roof of the orbit is placed the lacrimal gland.
Nasal region:
The surface boundary runs from the root of the nose to the inner eye corner and along the perimeter of the nasal wings toward the nasolabial groove. The foundation of this region is the bony and cartilaginous skeleton of the nose. The skin is thin on the root and the ridge of the nose, then thickens downward and contains numerous sebaceous and sweats glands, especially at the wings. The subcutaneous tissue is sparse and low in fat tissue in the upper part of the region, so the skin of the dorsum and root is easily movable against the base, while the apex and wings adhere more firmly to the perichondrium. Deep in the subcutaneous tissue on the dorsum and the wings is nasalis muscle, at the root of nose is found the procerus muscle.
The arterial supply comes from the branches of the angular artery (branch of the facial artery), the dorsal nasal artery (branch of the supratrochlear artery) and the infraorbital artery. Venous blood drains into the facial vein, as well as through the nasofrontal vein into superior ophthalmic vein and through deep connections into the veins of the walls of the nasal cavity.
Lymphatic drainage flows into the parotid and submandibular lymph nodes.
Sensory innervation is supplied by the infratrochlear, the anterior ethmoidal, and the infraorbital nerves from the 1st and 2nd trigeminal divisions. Muscles are innervated by the facial nerve.
Oral region:
The oral region is formed by the upper and lower lip. The region is bordered by the nasolabial groove and the mentolabial groove. The skin of the lips is tough and thick, less movable against the base. It contains numerous sweat and sebaceous glands and hairs in men beards.
The skin changes into mucosa of the oral cavity in the transitional zone of lips – the vermillion border. The skin is thin here and the epithelium does not keratinize. The redness of the lips is due to underlying blood vessels. Under the subcutaneous connective tissue is the orbicularis oris muscle, into which insert radially in the corners the surrounding facial muscles. This common insertion about 1 cm lateral to the angle of the mouth is called the modiolus.
Arterial supply to the lips is provided by the superior and inferior labial arteries, the branches of the facial artery. Venous blood drains predominantly to the facial vein. The lymph drains to the submandibular lymph nodes and from the center of the lower lip into the submental lymph nodes.
The upper lip has sensory innervation from the 2nd division of the trigeminal nerve (superior labial branches), and the lower lip from the mental nerve, a branch of the 3rd trigeminal division. Muscles are innervated by the facial nerve.
Buccal region:
The buccal region continues laterally from the lips. The anterior border is made by the nasolabial sulcus, the superior border is formed by the perimeter of the lower eyelid, and the edge of the mandibular body makes the inferior border.
The skin is thick, stretchable, and towards the lower eyelid gradually thins out. It contains numerous sweat and sebaceous glands. Subcutaneous tissue has an areolar structure and separates the skin from the muscles of facial expression.
The superficial layer of the muscles of facial expression is formed by the orbicularis oculi (orbicular part), the levator labii superioris alaeque nasi, the levator labii superioris, the zygomatic muscles, the risorius, the levator anguli oris, and the superior part of platysma. Underneath is the intermuscular space, a slit-like space between the superficial and deep muscle layers. This space is filled with loose connective fatty tissue that condenses dorsally, creating the buccal fat pad.
Blood vessels and nerves, arranged from the surface to the deep, are principally the facial artery, the facial vein, and their branches. The facial artery is palpable on the edge of the mandible, right in front of the anterior margin of the masseter muscle. At this point it can be easily compressed. The connection between the facial vein and the pterygoid plexus, is important for the spread of infection from the face to the intracranial veins.
Branches of the facial nerve emerge from the anterior margin of the parotid gland and supply the muscles of facial expression. Lymph is drained into the submandibular lymph nodes.
Over the anterior edge of the masseter muscle passes the parotid duct. It wraps the surface around the anterior edge of the buccal fat pad and pierces through the buccinator muscle and the mucosa of oral vestibulum.
The deep muscle layer is formed by the buccinator muscle, which underlies the entire region. Its surface is covered by the buccopharyngeal fascia.
The submucosal tissue of the face contains the buccal glands. The deepest layer is the mucosa lining of the oral vestibule.
Mental region:
This region is found between the mentolabial sulcus and the edge of the mandible. The subcutaneous tissue contains the chin group of muscles of facial expression, through which the mental nerve, the terminal branch of the inferior alveolar nerve, pierces toward the skin. The area where the mental nerve emerges from the mental foramen is the palpation point of the 3rd trigeminal branch.
Sources:
Stingl, J., Grim, M., & Druga, R. (2012). Regional anatomy. Galen.
