The side of the face, often referred to as the lateral or facial aspect, is a complex anatomical region that plays a crucial role in various functions, including facial expression, speech, and sensory perception. Understanding its intricate structure is essential for medical professionals, cosmetic surgeons, and even artists aiming to capture the human face's beauty and uniqueness. This article delves into the detailed anatomy of the face's side, highlighting key structures and their functions.
Before exploring the side of the face's anatomy, let's briefly discuss the face's basic structure and orientation. The face is divided into three main regions: the frontal (forehead), midline (nose, mouth, and chin), and lateral (sides) regions. The lateral region, our focus here, is bounded by thezygomatic arch superiorly, the mandible inferiorly, and extends from the midline to the lateral border of the skull.
Bony Framework of the Face's Side
The side of the face is primarily supported by the zygomatic, temporal, and mandibular bones, which collectively form the facial skeleton.
While the zygomatic bone, or cheekbone, forms the prominent arch of the cheek, the temporal bone forms the lateral skull's floor, housing the temporal fossa that accommodates the temporalis muscle. The mandible, or jawbone, forms the lower border and supports the lower teeth, enabling mastication and speech.
Zygomatic Bone and the Cheek
The zygomatic bone, derived from the Greek word 'zygon,' meaning 'yoke,' forms the cheek's promontory and is also known as the malar bone. It consists of a body, two processes (frontal and temporal), and two surfaces (malar and temporal). The malar surface projects forward to form the prominence of the cheek, while the temporal surface is divided into two parts: a squamous and a petsosal part, the latter articulating with the palatine bone of the nasal cavity.
Overlying the zygomatic bone is the vast temporalis muscle, responsible for jaw elevation during mastication. Inferior to this, the buccinator muscle flattens and thickens the cheek, aiding in facial expression and oral continence. The cheek itself is composed of subcutaneous fat, extending down to the palate's lateral aspect, and is covered by the thin and mobile dermal layer.
Temporal Bone and the Temporal Fossa
The temporal bone is one of the skull's seven bones and is divided into four parts: the squamous, mastoid, zygomatic, and petromastoid processes. The squamous part forms the lateral aspect of the skull's base and contains the temporal fossa, housing the temporalis muscle. The mastoid process, the temporal bone's lowest and most prominent part, serves for muscle attachment and provides a site for faciplasty incisions.
The temporal fossa is limited superiorly by the temporal line of the frontal bone, medially by the squamous part of the temporal bone, inferiorly by the zygomatic arch, and laterally by the bony external auditory meatus. It contains the temporalis muscle, its tendon, and the temporomandibular joint, responsible for connecting the mandible to the skull.
Muscular Anatomy of the Face's Side
The side of the face is characterized by a complex interplay of muscles, responsible for facial expression, mastication, and speech. These muscles can be categorized into two groups: the muscles of facial expression and the muscles of mastication.
While the muscles of facial expression are thin, superficial, and supply the skin, the muscles of mastication are larger, deeper, and involved in jaw movement and mastication.
Muscles of Facial Expression
The muscles of facial expression originate from the facial nerve's seventh cranial nerve and are responsible for various facial expressions, such as smiling, frowning, and raising eyebrows. The side of the face is primarily innervated by the temporal and zygomatic branches of the facial nerve.
Key muscles involved include the orbicularis oculi, responsible for eye closure and blinking; the orbicularis oris, closing the mouth; the zygomaticus major, elevating the mouth's corners into a smile; and the corrugator supercilii, pulling the eyebrows medially during frowning.
Muscles of Mastication
The muscles of mastication are responsible for jaw movement and mastication. They consist of the temporalis, masseter, pterygoid, and digastric muscles. The temporalis muscle, the largest muscle of mastication, originates from the temporal fossa and inserts into the coronoid process of the mandible.
It is responsible for jaw elevation and retraction. The masseter muscle, located in the face's anterior part, originates from the zygomatic arch and inserts into the ramus of the mandible. It is the most powerful jaw-closing muscle and plays a significant role in mastication. The pterygoid muscles, situated posterior to the maxilla, are responsible for jaw mobility, while the digastric muscles, located in the neck, help in lowering the jaw.
Understanding the intricate anatomy of the face's side is crucial for medical professionals, cosmetic surgeons, and facial reconstructive specialists. It facilitates accurate diagnosis, effective treatment, and reconstruction following trauma or disease. Furthermore, insights into facial anatomy help artists capture the human face's beauty and expressiveness, while archaeologists use facial features to reconstruct ancient faces and understand human evolution.