The temporal and infratemporal fossae are interconnected spaces on the lateral side of the head (Fig. 8.135). Their boundaries are formed by bone and soft tissues.
The temporal fossa is superior to the infratemporal fossa, above the zygomatic arch, and communicates with the infratemporal fossa below through the gap between the zygomatic arch and the more medial surface of the skull.
The infratemporal fossa is a wedge-shaped space deep to the masseter muscle and the underlying ramus of the mandible. Structures that travel between the cranial cavity, neck, pterygopalatine fossa, floor of the oral cavity, floor of the orbit, temporal fossa, and superficial regions of the head pass through it.
Of the four muscles of mastication (masseter, temporalis, medial pterygoid, and lateral pterygoid) that move the lower jaw at the temporomandibular joint, one (masseter) is lateral to the infratemporal fossa, two (medial and lateral pterygoid) are in the infratemporal fossa, and one fills the temporal fossa.
Bones that contribute significantly to the boundaries of the temporal and infratemporal fossae include the temporal, zygomatic, and sphenoid bones, and the maxilla and mandible (Figs. 8.136 and 8.137).
Parts of the frontal and parietal bones are also involved.
The squamous part of the temporal bone forms part of the bony framework of the temporal and infratemporal fossae.
The tympanic part of the temporal bone forms the posteromedial corner of the roof of the infratemporal fossa, and also articulates with the head of the mandible to form the temporomandibular joint.
The lateral surface of the squamous part of the temporal bone is marked by two surface features on the medial wall of the temporal fossa: a transversely oriented supramastoid crest, which extends posteriorly from the base of the zygomatic process and marks the posteroinferior border of the temporal fossa; and a vertically oriented groove for the middle temporal artery, a branch of the superficial temporal artery.
Two features that participate in forming the temporomandibular joint on the inferior aspect of the root of the zygomatic process are the articular tubercle and the mandibular fossa. Both are elongate from medial to lateral. Posterior to the mandibular fossa is the external acoustic meatus. The tympanic part of the temporal bone is a flat concave plate of bone that curves inferiorly from the back of the mandibular fossa and forms part of the wall of the external auditory meatus.
When viewed from inferiorly, there is a distinct tympanosquamous fissure between the tympanic and squamous parts of the temporal bone. Medially, a small slip of bone from the petrous part of the temporal bone insinuates itself into the fissure and forms a petrotympanic fissure between it and the tympanic part (Fig. 8.136).
The chorda tympani nerve exits the skull and enters the infratemporal fossa through the medial end of the petrotympanic fissure.
The parts of the sphenoid bone that form part of the bony framework of the infratemporal fossa are the lateral plate of the pterygoid process and the greater wing (Fig. 8.136). The greater wing also forms part of the medial wall of the temporal fossa.
The greater wings extend one on each side from the body of the sphenoid. They project laterally from the body and curve superiorly. The inferior and lateral surfaces form the roof of the infratemporal fossa and the medial wall of the temporal fossa, respectively.