ANATOMY AND PHYSIOLOGY
Situated on the sides and the base of the cranium, the temporal bone is comprised of four major segments: the squamous, tympanic, mastoid, and petrous parts. It houses portions of the external ear, middle ear, inner ear--including the cochlea and the vestibular apparatus--as well as the seventh and eighth cranial nerves. Its primary function is surrounding the ear and protecting the nerves and structures within it, as they play a key role in controlling hearing and balance. A hard and rigid structure, the temporal bone also has several bony projections, including the zygomatic and styloid processes. The squamous portion is the uppermost landmark of the temporal bone, and can be described as a thin plate of bone with a large, fan-like appearance (The). The long and arched zygomatic process protrudes from the lower part of the squamous portion and articulates with the zygomatic bone, which forms the prominent part of the cheek and the outer side of the eye socket (Yu). The squamous portion protects the temporal lobe of the brain and articulates with the parietal bone. Just below, the tightly packed petrous portion forms the part of skull base between the sphenoid and occipital bones. It is a pyramid-shaped landmark with an apex and a base, and it houses the middle and inner ear structures while forming the floor of the cranial cavity. The bulge of bone located just behind the pinna is the mastoid portion, and it contains an air-filled cavity structure known as the mastoid air cell system (Mastoid). This system aids in regulating pressure within the ear as well as protecting the middle ear. The tympanic portion is the outermost landmark of the temporal bone, and forms the floor and wall of the external ear canal. Small and curved, the tympanic portion's anterior (forwardmost) surface is continuous with the squamous part of the temporal bone, and the tympanic portion encloses a part of the middle ear while supporting the tympanic membrane. Just below the external auditory canal, the styloid process serves as an anchor point for several muscles associated with the speech (Knipe). The temporomandibular joint plays a key role in the function of the temporal bone, as it acts as the hinge joint between the temporal bone and the lower jaw (Temporomandibular). It works to elevate the jaw, allowing it to open and close.
|