Table of ContentsView AllTable of ContentsAnatomyFunctionAssociated ConditionsRehabilitation
Table of ContentsView All
View All
Table of Contents
Anatomy
Function
Associated Conditions
Rehabilitation
The temporal bones are two bony structures that shape the sides and base of the skull (cranium). They are located to the side of (lateral to) the temporal lobes of the brain’s cerebral cortex. The temporal bones ensure that the cranium is properly supported and help protect the important structures inside your head.
Blunt trauma or fracture of these bones can lead to serious complications andbrain injury, damage to the inner ear, as well as facial nerve problems. In addition,middle ear infectionscan spread to this bone.
Bone and Muscle Anatomy
The temporal bone is composed of five parts: the squama, the petrous, mastoid, and tympanic parts, as well as the styloid process.These parts attach to muscles involved in chewing and other functions.
Squama
Forming the front, upper part of the temporal bone, thesquamais thin and often translucent.The outer surface is smooth and forms a convex shape, and via the temporal line (a curved ridge running to the back and upward), it attaches to the temporalis muscle, which helps with chewing.
The front end of the squama is serrated (jagged) and connects with thezygomatic bone—one of two paired bones that form the cheeks and the sidewalls of the orbits (the openings where the eyeballs sit).
The bottom end of this bone connects to the masseter, another major muscle for chewing. In addition, this part of the temporal bone is connected to ligaments regulating muscles in the upper portion of themandible, or jawbone.
Mastoid Part
Forming the rear part of the temporal bone, the mastoid part’s outer surface is rough. It attaches to muscles that regulate the motion of eyebrows (occipitalis muscle) as well as those above the ear (superior auricular muscle).
The mastoid part is perforated and includes the mastoid foramen, an opening that allows a vein to access the transverse sinus, the area on each side of the head that drains blood from the back of the head. The vein can also access an artery that provides oxygenated blood to the layer of tissue tasked with protecting the brain (dura mater).
Moving downward, this part becomes a cone-shaped projection—themastoid process—which connects to muscles essential for head movement. The upper part of this portion can be hollow in places, but these openings grow smaller as you move down.
Petrous Part
The petrous part is also known as the “pyramid part” because of its shape. The petrous part sits at the base of the skull between the occipital and sphenoid bones (the portion just beneath the temples).
Moving upward, the petrous part has a base fused with the squama and mastoid portion and an apex (tip) that sits between theoccipitaland sphenoid bones. The latter form the carotid canal, which allows important arteries to access the brain.
The petrous part’s anterior (front) surface forms the rear portion of the middle fossa, a cavity in the base of the skull. A thinner portion goes over the tympanic cavity, the hole surrounding the middle ear bones.
The posterior (rear) portion of the petrous part accesses the posterior fossa, which is the opening at the base of the skull that cradles the cerebellum and brain stem. At its center, there’s an opening—the internal acoustic meatus—that allows nerves and arteries to pass through.
Tympanic Part
The tympanic part is the curved portion of bone beneath the squama and in front of the mastoid process. It forms a major part of the external acoustic meatus, which is the pathway from the outer to the inner ear.
The middle portion of the tympanic part contains the tympanicsulcus, a groove that attaches to the tympanic membrane, better known as the eardrum. At its rear surface, the tympanic part forms the rear boundary of the mandibular fossa, a groove that connects with the jaw bone.
The outside surface of the tympanic part is rough and attaches to the cartilage portion of the acoustic meatus. The interior fuses with the petrous portion just below the ear canal. Thin and sharp in its middle portion, it splits to enclose a portion of the styloid process.
Styloid Process
The styloid process is a narrow projection of bone coming out of the temporal bone. Variable in length, it is angled downward and forward.
This thin needle-shaped bone projects from the inferior (lower) part of the petrous temporal bone and attaches to thestylohyoidligament and the stylohyoid,stylopharyngeus, and styloglossus muscles, involved with chewing motions.
The outer side of the styloid process is next to theparotid gland(the source of saliva), which is also the site where theexternal carotid artery(which supplies features in the face and brain) crosses.
Notably, the temporal bone attaches to the joint of the jaw bone—thetemporomandibularjoint—and is fused with other bones of the skull, including the occipital bone on the lower rear side, theparietalbone above that, the sphenoid bone on its front side, and thezygomatic (cheek) bone.
Caspar Benson/Getty Images
Anatomical Variations
Variations in the anatomy of the temporal bone are not uncommon and usually have to do with the size and shape of its many openings. The most commonly observed variations include:
The temporal bone provides structural support for the skull, while protecting the cerebrum of the brain and surrounding membranes. In addition, this bone surrounds the middle and inner portions of the ear.
The lower portion of the temporal bone connects with the mandible or jawbone to allow the mouth to open and close. Notably, mostcranial nerves—nerves associated with sensation and perception—pass over this bone.
Given their position on the sides and back of the skull, these bones also connect to several important muscle groups. In particular, the squama and styloid processes are connected to the temporalis and masseter muscles that are involved with chewing.
Furthermore, the more rear-facing parts of the temporal function are linked to thesternocleidomastoidandsplenius capitismuscles, associated with neck and head motion.
Finally, via its mastoid process, the temporal bone is connected to the suprahyoid muscle, which is essential for swallowing.
A number of medical issues can arise in this part of the skull.
Temporal Bone Fracture
While the temporal bone is relatively thick, blunt trauma can cause a fracture. This can lead to a number of serious complications, including damage to hearing, vertigo, facial paralysis (due to damage to the facial nerve), and bleeding in the ear, as well as bone bruising. Notably, fractures can also lead to the leaking of cerebral spinal fluid.
Pterion Fracture
More common are fractures of thepterion, which is where the temporal bone joins with other major bones of the skull: the parietal, frontal, and sphenoid. This juncture is the weakest point of the skull.
Themiddle meningeal artery, which supplies the dura and skull, passes right behind it. If injured or lacerated, blood collects and dangerously increases intracranial pressure. This can lead to seizures, nausea, vomiting, and limb weakness, among other symptoms.
Infection
Because the mastoid portion of the temporal bone is porous, middle ear infections spread to it, leading to a condition calledmastoiditis. If untreated, the infection can spread further into the middle cranial fossa, a major region of the interior of the skull, and even the brain itself, causingmeningitis.
Depending on the severity of trauma and fracture of the skull, surgery may be necessary to correct the issue and take on bleeding and other issues that may arise.
If trauma or fracture causes damage to thefacial nerve, as is often the case, nerve decompression surgery may be necessary to repair it and ease pressure.
This, along with more conservative approaches, is effective in taking on facial paralysis; however, the decision to move ahead needs to be carefully weighed.
Leaking of cerebrospinal fluid following a fracture of the temporal bone increases the risk of meningitis, a type of brain infection. This issue can also impact structures in the ear and lead to fluid leaks.
These cases are best handled without surgery. Treatment often involves the use of antibiotics, rest, and elevation of the head during healing. It may also include other means to return cerebrospinal fluid levels to normal. If a leak doesn’t close, surgery is needed to correct the problem.
In more extreme cases where the middle meningeal artery is lacerated due to a fracture of the temporal bone, prompt surgery may be required to take on the resulting bleeding. If the case is more moderate, doctors may prescribe diuretic drugs.
Summary
The temporal bones help to shape the face and protect vital structures inside of your head. These bones also attach to muscles that are used in chewing and other movements of the mouth and face. Variations in temporal bone anatomy are not uncommon.
Damage to the temporal bone can occur due to fracture or infection. Treatment may involve surgery or the use of antibiotics to prevent more serious illness or injury.
12 Sources
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