The infratemporal fossa is a complex anatomical space situated deep within the skull, playing a central role in various functions of the head and neck. While not immediately visible, this region acts as a conduit, housing numerous structures that facilitate movement, sensation, and blood supply to areas of the face and jaw. Understanding this space is important for appreciating the mechanics of the human head.
Understanding Its Location
The infratemporal fossa is an irregularly shaped, wedge-like cavity located at the side of the skull, beneath the temporal fossa and deep to the ramus of the mandible (lower jawbone). It is positioned below and slightly inward from the zygomatic arch (cheekbone). This space is not fully enclosed by bone in all directions, as it opens towards the neck region inferiorly, lacking a true anatomical floor.
Its boundaries are formed by a combination of bones and muscles. Anteriorly, it is bordered by the posterior surface of the maxilla (upper jawbone). The medial wall is primarily defined by the lateral pterygoid plate of the sphenoid bone, a butterfly-shaped bone, along with certain muscles like the tensor veli palatini. Laterally, the ramus of the mandible forms its boundary.
Superiorly, the roof is mainly composed of the greater wing of the sphenoid bone and a small part of the temporal bone. This roof contains openings, such as the foramen ovale and foramen spinosum, which serve as passages for nerves and blood vessels connecting to the cranial cavity. The posterior boundary is less defined, involving parts of the tympanic bone and the styloid process of the temporal bone. The fossa also communicates with several other cranial regions, including the temporal fossa, the pterygopalatine fossa, and the orbit, through various fissures and foramina.
Structures Housed Within
The infratemporal fossa contains anatomical components, including muscles, nerves, and blood vessels, supporting facial and oral functions. Among the structures are the muscles of mastication. Specifically, the medial and lateral pterygoid muscles are located entirely within this fossa, while the lower part of the temporalis muscle also extends into this space. The masseter muscle, though superficial, is also closely associated with this region.
The fossa is a pathway for several nerves, primarily branches of the trigeminal nerve (Cranial Nerve V), which is responsible for sensation in the face and motor functions like chewing. The mandibular nerve (CN V3), a division of the trigeminal nerve, enters the fossa through the foramen ovale and then divides into multiple branches. These branches include motor nerves that supply the muscles of mastication, as well as sensory nerves like the inferior alveolar nerve (providing sensation to lower teeth and chin), the lingual nerve (for general sensation and taste from the tongue), and the buccal nerve (for sensation from the cheek). The chorda tympani, a branch of the facial nerve (Cranial Nerve VII), also passes through this fossa and joins the lingual nerve, contributing to taste sensation and parasympathetic functions. The otic ganglion, a cluster of nerve cell bodies involved in parasympathetic innervation to the parotid gland, is also located here.
A blood vessel traversing the infratemporal fossa is the maxillary artery, a terminal branch of the external carotid artery. This artery gives rise to several branches within the fossa, such as the middle meningeal artery (supplying the dura mater, the protective membrane of the brain), the inferior alveolar artery (supplying the lower jaw and teeth), and the deep temporal arteries (supplying the temporalis muscle). Complementing the arterial supply is the pterygoid venous plexus, a network of veins that surrounds the maxillary artery and the pterygoid muscles. This plexus collects blood from various deep structures of the head and drains into the maxillary vein, which then contributes to the retromandibular vein.
Its Role in Body Function
The infratemporal fossa serves as an anatomical hub, facilitating physiological processes through the coordinated action of its housed structures. Its primary role centers around mastication. The medial and lateral pterygoid muscles, along with parts of the temporalis muscle, are directly responsible for the movements of the mandible. The lateral pterygoid muscle, for instance, initiates the opening of the mouth and assists in side-to-side movements of the jaw for grinding food. The medial pterygoid muscle works with the masseter and temporalis muscles to elevate the mandible, closing the jaw and enabling the biting force required for chewing.
Sensory functions are important within this region, primarily mediated by branches of the mandibular nerve. The inferior alveolar nerve provides sensation to the lower teeth. The lingual nerve transmits general sensation and taste from the anterior two-thirds of the tongue for distinguishing flavors and feeling food textures. The buccal nerve conveys sensory information from the inner cheek, playing a role in oral comfort and the positioning of food during chewing.
The blood vessels within the infratemporal fossa supply oxygen and nutrients to deep facial structures. The maxillary artery and its branches provide arterial supply to the muscles of mastication, teeth, and surrounding bones. The middle meningeal artery, a branch of the maxillary artery, supplies blood to the dura mater, the protective membrane of the brain. The pterygoid venous plexus contributes to venous drainage of the deep face, removing deoxygenated blood and waste products from these tissues. The contractions of the lateral pterygoid muscle assist this venous plexus in pumping blood back towards the heart.
Common Clinical Considerations
The infratemporal fossa, despite its protected location, can be involved in various clinical conditions due to its complex anatomy and the structures it contains. Infections are a concern, often originating from dental issues, such as mandibular molars or after tooth extractions. These can spread into this space, potentially forming abscesses. Such infections can be challenging to diagnose due to non-specific symptoms like pain, swelling, and trismus (difficulty opening the mouth).
The close proximity of the pterygoid venous plexus to the cavernous sinus, a venous channel within the skull, poses a risk for infection spread. An infection in the infratemporal fossa could track through the emissary veins connecting the plexus to the cavernous sinus, leading to serious intracranial complications like cavernous sinus thrombosis. Trauma to the facial region can also impact the infratemporal fossa, potentially damaging the nerves or blood vessels within. Injuries to the mandible or maxilla, for instance, could affect structures in this area.
Nerve impingement or injury within the fossa can lead to functional deficits. Given that the mandibular nerve and its branches pass through this space, conditions affecting this nerve can result in altered sensation in the lower face, teeth, and tongue, or weakness in the muscles of mastication. Tumors, though rare, can also arise within or spread into the infratemporal fossa from adjacent regions, such as the nasopharynx or sphenoid sinus. These growths can compress or displace the neurovascular structures, leading to a range of symptoms depending on the affected components.
The infratemporal fossa’s anatomical positioning makes it a region of interest for surgeons. Its deep location and the structures it houses require specialized surgical approaches for accessing and treating conditions within it. Surgical procedures in this area require careful planning to navigate around nerves and blood vessels. Understanding the relationships of the structures within the infratemporal fossa is important for accurate diagnosis and effective management of various medical conditions.