Anatomy of Temporal Bone. The temporal bone is a paired symmetrical bone which forms the lower lateral walls of the human skull. It is a composite structure consisting of four parts, each ossifying independently and later fuses with each other.
Parts of temporal bone.
- Squamous
- Petro-mastoid
- Tympanic
- Styloid.
It houses important internal ear, and middle ear structures and the majority of the cranial nerves pass through it. It articulates inferiorly with the mandible, forming the synovial temporomandibular joint of the jaw. The temporal, parietal and frontal bones together form the pterion, which is the weakest part of the skull.
Squamous part.
Squamous part. It is the largest and superior most part of temporal bone and forms the lateral wall of the middle cranial fossa. It’s thin, translucent, shell-like plate of bone and interfaces with the parietal bone superiorly and with the zygomatic process and the sphenoid anteriorly.
Squamous part presents
- Lateral temporal surface – External surface creates the floor of temporal fossa and there is a groove through which middle temporal artery runs.
- Cerebral medial surface – Internal surface is located in contact together with the temporal lobe of the brain. It’s grooved by the anterior and posterior branches of the middle meningeal artery.
- Superior border – The temporal, parietal and frontal bones together form the pterion, which is the weakest part of the skull.
- Anteroinferior border – Anteriorly, inferior surface of squamous part forms the posterolateral aspect of the infratemporal fossa, And on its lateral surface, suprameatal crest delineates the lower aspect of the attachment of the temporalis fascia, limiting the origin of the temporalis muscle and, together with a small triangle of bone at the posterosuperior aspect of the external auditory meatus, the suprameatal (McEwan’s) triangle, are important superficial landmarks for cortical mastoidectomy. The suprameatal triangle, a depression marking the position of the mastoid antrum (which is medial to the triangle at a depth of approximately 1.25 cm). Medial surface is grooved by a sulcus for middle meningeal artery and lateral surface for middle temporal artery.
- Zygomatic process – The zygomatic process projects laterally from the temporal surface and joins with temporal process of the zygomatic bone to form zygomatic arch.
- Mandibular fossa is a depression which houses the synovial temporomandibular joint lies below the zygomatic process and behind the articular eminence. Temporalis muscle originates from the lower part of the squamous bone. The squamous part together with petrous bone forms the anterior aspect of the external ear canal. The posterior aspect of the external ear canal is formed by the curved C-shaped tympanic part of the temporal bone.
Petro-mastoid part
1. Petrous (rock-like) part: It is present between the occipital and sphenoid bones in the skull base. It forms part of cranial floor and separates middle cranial fossa to posterior cranial fossa. It houses internal ear, middle ear and mastoid antrum, which it safely shields due to its high bone density. It also includes carotid canal for internal carotid artery.
Boundaries.
It is a pyramid shaped structure, having a base, an apex, three surfaces and three edges or margins.
- Base. It is fused with the squamous part.
- Apex. Forms the posterolateral margin of foramen lacerum and presents internal opening of carotid canal.
- Surfaces.
- Anterior surface forms the posterior part of middle cranial fossa. It presents tegmen tympani, arcuate eminence, hiatus for greater and lesser petrosal nerve, trigeminal impression.
- Posterior surface forms the anterior wall of the posterior cranial fossa. It presents an internal acoustic opening which leads to the internal acoustic meatus and external opening of the vestibular aqueduct.
- Inferior surface. It is a quadrangular area viewed in the base of the skull. It is located between the basilar part of the occipital bone and greater wing of sphenoid. It presents the lower opening of the carotid canal and jugular fossa.
Borders.
Superior border: It is a long sharp crest which intervenes between middle and posterior cranial fossae. It presents the groove for the superior petrosal sinus. Abducent nerve crosses at its medial end.
Anterior border: It can be divided into two parts. Medial part articulates with greater wing of sphenoid while the lateral part joins squamous bone with a suture – petrosquamosal suture.
Posterior border: It presents groove which lodges the inferior petrosal sinus. Its lateral part creates the superolateral boundary of the jugular foramen.
2. Mastoid part: It is a projection seen inferiorly on the lateral surface of temporal bone. It is formed by squamous portion (laterally) and a petrous portion (medially) separated by Korner’s (petrosquamous) septum. It is located posteroinferior to the squamous part and includes mastoid antrum and its air cells, which communicate with the middle ear cavity.
It presents digastric notch for connection to the posterior belly of digastric muscle and mastoid process for attaching the sternocleidomastoid, splenius capitis and longissimus capitis muscles. Mastoid process is present just posterior to the external auditory opening and it is not fully developed in children. A more horizontal postauricular incision should be given to prevent injury to the facial nerve. The mastoid foramen, is an opening situated posteriorly on the mastoid process, is passed by the mastoid emissary vein for venous drainage and one or two mastoid arteries.
Tympanic part
Tympanic part is situated lateral to the petrous bone lies inferiorly to the squamous, and anteriorly to the petromastoid part.
- The posterosuperior surface forms anterior wall, the floor and part of the posterior wall of the bony ear canal.
- Anteroinferior surface forms the posterior boundary of the mandibular fossa.
- Medially, it houses the circular groove, ‘tympanic sulcus’ for the attachment of the tympanic membrane.
- Laterally, tympanic bone boundary ends at the cartilaginous EAC.
Tympanic bone is attached to squamous part and mastoid part forming the tympanosquamous anteriorly and tympanomastoid sutures posteriorly. Chorda tympani, anterior tympanic artery and anterior process of malleus traverses the petrotympanic fissure. Arnold’s nerve traverses tympanomastoid suture. The inferior aspect of the tympanomastoid suture line is an important operative landmark for identifying the facial nerve as it exits the stylomastoid foramen.
Inferiorly, the vaginal process splits to enclose the root of the styloid process
Styloid part.
Styloid process is a long, slender, pointed piece of bone originating from the inferior aspect of the fusion of the tympanic and petrous bones and located in front of the jugular fossa. Its normal length is approximately 2.5 cm. It projects downwards and forwards, giving attachment to several muscles and ligaments.
- Ligaments – Stylohoid, stylomandibular
- Muscles – Styloglossus, stylohyoid, stylopharyngeal.
Stylomandibular ligament extends from anterior surface of apex of styloid process to the posterior surface of the angle of mandible. This ligament separates parotid gland from submandibular gland & medial pterygoid muscle.
The stylomastoid foramen is a round opening situated between the styloid and the mastoid processes. It transmits the facial nerve (CN VII) and the stylomastoid artery.
Anatomy of Temporal Bone Anatomy of Temporal Bone Anatomy of Temporal Bone Anatomy of Temporal Bone Anatomy of Temporal Bone
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Learning resources.
- Scott-Brown, Textbook of Otorhinolaryngology Head and Neck Surgery.
- Glasscock-Shambaugh, Textbook of Surgery of the Ear.
- Susan Standring, Gray’s Anatomy.
- Logan Turner, Textbook of Diseases of The Nose, Throat and Ear Head and Neck Surgery.
- P L Dhingra, Textbook of Diseases of Ear, Nose and Throat.
- Hazarika P, Textbook of Ear Nose Throat and Head Neck Surgery Clinical Practical.
- Mohan Bansal, Textbook of Diseases of Ear, Nose and Throat Head and Neck surgery.
Author:
Dr. Rahul Kumar Bagla
MS & Fellow Rhinoplasty & Facial Plastic Surgery.
Associate Professor & Head
GIMS, Greater Noida, India
msrahulbagla@gmail.com
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