The temporal bone plays an important part in the lower lateral walls of the skull, containing the middle and inner portions of the ear and being crossed by many of the cranial nerves. Interaction with the mandible completes the formation of the temporomandibular joint. It is essential to gain an understanding of the anatomy of the temporal bone, including the component parts and articulations, to gain a full pictue of its clinical correlations.
When looking at the temporal bone specifically, it is made up of five main anatomical parts. The squamous, tympanic and petromastoid parts form the majority of the bone, while the zygomatic and styloid processes are what projects outwards. Below, we take a closer look at each of these parts.
Also referred to as the squama temporalis, the squamous part of the temporal bone is the largest part. It is flat, plate-like and located in the superior position. When looking at the outer surface of the squamous bone, it is convex in shape and forms part of the temporal fossa. The lower part of the squamous bone serves as the origin of the temporalis muscle, with the bone articulating with the sphenoid bone anteriorly and the parietal bone laterally.
The zygomatic process of the temporal bone is projected anteriorly and comes from the lower part of the squama temporalis. It interacts with the temporal process of the zygomatic bone to form the zygomatic arch, which is the easily-palpable 'cheek bone'. The articular tubercle, found at the anterior boundary of the mandibular fossa, is formed at the connection of the zygomatic process and temporal bone. Masseter muscles have fibres that attach to the lateral surface of the zygomatic process.
In terms of location, the tympanic part of the temporal bone lies inferiorly to the squamous and anteriorly to the petromastoid. It has the vital role of encircling the external auditory opening, which leads into the external auditory meatus of the external ear.
The styloid process is placed immediately underneath the opening to the auditory meatus and serves to form an attachment point for muscles and ligaments such as the stylomandibular ligament of the TMJ.
As the most posterior of the temporal bone parts, the petromastoid can be split into a mastoid and petrous parts. The mastoid process, located on the inferior projecting bone, is easily palpable just behind the ear. It acts as a site of attachment for many muscles such as the sternocleidomastoid. The mastoid air cells, which are hollowed areas within the temporal bone, are also worth noting. These act as reservoirs of air to enable pressure to be equalised within the middle ear in the case of auditory tube dysfunction, and can also become infected, known as mastoiditis. The petrous part of the petromastoid is pyramidal shaped and is located at the base of the temporal bone, containing the inner ear.
Due to the role of the temporal bone in forming the temporomandibular joint, the temporalis and masseter muscles of mastication have fibres that attach to the temporal bone. The mastoid process of the temporal bone is also a major site of muscle attachment, and some key muscular attachments are outlined in the table below.
The temporal bone is a complex bone that is located in the skull and plays a critical role in many different functions of the human body. It is best known as containing the middle ear structures and playing a role in the formation of the temporomandibular joint (TMJ). In addition to these roles, the temporal bone plays a critical role in the attachment of many muscles, including the masseter, temporalis, and sternocleidomastoid. It also contains the petrous part, which houses the inner ear, and the mastoid part, which contains the mastoid air cells.
The temporal bone can be divided into several parts, which all play important roles. The zygomatic process arises from the lower portion of the squama temporalis and articulates with the zygomatic bone, forming the zygomatic arch. In addition, a small articular tubercle is formed at the attachment of the zygomatic process to the temporal bone, forming the anterior boundary of the mandibular fossa. The tympanic part of the temporal bone lies beneath the squamous part and surrounds the external auditory opening. The styloid process is located immediately beneath this opening and serves as an attachment point for muscles and ligaments, such as the stylomandibular ligament. The mastoid part of the temporal bone is located posteriorly and contains the mastoid process, which is palpable just behind the ear. Also present in the mastoid part are the mastoid air cells, which act as a reservoir of air and can become infected in cases of mastoiditis.
The temporal bone serves as a point of attachment for many muscles due to its involvement in the formation of the TMJ. The muscles of mastication, including the temporalis and masseter muscles, attach to the temporal bone. In addition to this, the mastoid process of the temporal bone serves as a major site of muscle attachment. A table outlining some of the key muscular attachments to the temporal bone is included below.
The temporal bone also articulates with the mandible to form the temporomandibular joint. In addition to this, the squamous part of the temporal bone articulates with the sphenoid bone anteriorly and the parietal bone laterally. The zygomatic process articulates with the zygomatic bone to form the zygomatic arch.
Middle ear infections (otitis media) can spread to the mastoid air cells, which are hollowed out areas within the temporal bone. Due to their porous nature, they are a suitable site for pathogenic replication and can become infected, resulting in mastoiditis. When mastoiditis is suspected, pus must be drained from the air cells. It is important to exercise caution when doing this so that the nearby facial nerve is not damaged.
The temporal bone is relatively strong and thus is usually only fractured as a result of blunt trauma to the skull. The skull is weakest at the point where the temporal, parietal, frontal, and sphenoid bones meet, known as the pterion. The middle meningeal artery (MMA) lies beneath the pterion and supplies the skull and dura mater. A fracture at the pterion can injure or completely lacerate the MMA, resulting in a buildup of blood in between the dura mater and the skull, known as an extradural haematoma. This can cause an increase in intracranial pressure, leading to a variety of symptoms such as nausea, vomiting, seizures, bradycardia, and limb weakness. In minor cases, this increase in intracranial pressure is treated with diuretics, but surgical intervention is required in cases of major haemorrhage.
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