The temporal bones are situated at the sides and base of the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

, and lateral to the

temporal lobe The temporal lobe is one of the four Lobes of the brain, major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe ...

s of the

cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consistin ...

. The temporal bones are overlaid by the sides of the head known as the

temples A temple (from the Latin ) is a building reserved for spiritual rituals and activities such as prayer and sacrifice. Religions which erect temples include Christianity (whose temples are typically called churches), Hinduism (whose temples ...

, and house the structures of the

ear An ear is the organ that enables hearing and, in mammals, body balance using the vestibular system. In mammals, the ear is usually described as having three parts—the outer ear, the middle ear and the inner ear. The outer ear consists of ...

s. The lower seven

cranial nerves Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and f ...

and the major vessels to and from the

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

traverse the temporal bone.

Structure

The temporal bone consists of four parts— the

squamous Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellula ...

mastoid The mastoid part of the temporal bone is the posterior (back) part of the temporal bone, one of the bones of the skull. Its rough surface gives attachment to various muscles (via tendons) and it has openings for blood vessels. From its borders, ...

, petrous and tympanic parts. The squamous part is the largest and most superiorly positioned relative to the rest of the bone. The

zygomatic process The zygomatic processes are three processes (protrusions) from other bones of the skull which each articulate with the zygomatic bone. The three processes are: * Zygomatic process of frontal bone from the frontal bone * Zygomatic process of max ...

is a long, arched process projecting from the lower region of the squamous part and it articulates with the

zygomatic bone In the human skull, the zygomatic bone (from grc, ζῠγόν, zugón, yoke), also called cheekbone or malar bone, is a paired irregular bone which articulates with the maxilla, the temporal bone, the sphenoid bone and the frontal bone. It is s ...

. Posteroinferior to the squamous is the mastoid part. Fused with the squamous and mastoid parts and between the sphenoid and occipital bones lies the petrous part, which is shaped like a pyramid. The tympanic part is relatively small and lies inferior to the squamous part, anterior to the mastoid part, and superior to the styloid process. The styloid, from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''stylos'', is a phallic shaped pillar directed inferiorly and anteromedially between the

parotid gland The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the ma ...

and

internal jugular vein The internal jugular vein is a paired jugular vein that collects blood from the brain and the superficial parts of the face and neck. This vein runs in the carotid sheath with the common carotid artery and vagus nerve. It begins in the poste ...

. An elongated or deviated styloid process can result from

calcification Calcification is the accumulation of calcium salts in a body tissue. It normally occurs in the formation of bone, but calcium can be deposited abnormally in soft tissue,Miller, J. D. Cardiovascular calcification: Orbicular origins. ''Nature Ma ...

of the stylohyoid ligament in a condition known as ''

Eagle syndrome Eagle syndrome (also termed stylohyoid syndrome, styloid syndrome, styloid-stylohyoid syndrome, or styloid–carotid artery syndrome) is a rare condition commonly characterized but not limited to sudden, sharp nerve-like pain in the jaw bone and ...

''.

Borders

Development

The temporal bone is

ossified Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...

from eight centers, exclusive of those for the

internal ear Internal may refer to: *Internality as a concept in behavioural economics *Neijia, internal styles of Chinese martial arts *Neigong or "internal skills", a type of exercise in meditation associated with Daoism *''Internal (album)'' by Safia, 2016 ...

and the tympanic ossicles: one for the squama including the zygomatic process, one for the tympanic part, four for the petrous and mastoid parts, and two for the styloid process. Just before the end of prenatal development

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the temporal bone consists of three principal parts: # The squama is ossified in membrane from a single nucleus, which appears near the root of the zygomatic process about the second month. # The petromastoid part is developed from four centers, which make their appearance in the cartilaginous ear capsule about the fifth or sixth month. One (proötic) appears in the neighborhood of the eminentia arcuata, spreads in front and above the

internal auditory meatus The internal auditory meatus (also meatus acusticus internus, internal acoustic meatus, internal auditory canal, or internal acoustic canal) is a canal within the petrous part of the temporal bone of the skull between the posterior cranial fossa ...

and extends to the apex of the bone; it forms part of the cochlea, vestibule, superior semicircular canal, and medial wall of the tympanic cavity. A second (opisthotic) appears at the promontory on the medial wall of the tympanic cavity and surrounds the fenestra cochleæ; it forms the floor of the tympanic cavity and vestibule, surrounds the carotid canal, invests the lateral and lower part of the cochlea, and spreads medially below the internal auditory meatus. A third (pterotic) roofs in the tympanic cavity and antrum; while the fourth (epiotic) appears near the posterior semicircular canal and extends to form the mastoid process (Vrolik). # The tympanic ring is an incomplete circle, in the concavity of which is a groove, the tympanic sulcus, for the attachment of the circumference of the

eardrum In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear The outer ear, external ear, or auris externa is the extern ...

(tympanic membrane). This ring expands to form the tympanic part, and is ossified in membrane from a single center which appears about the third month. The styloid process is developed from the proximal part of the cartilage of the second branchial or hyoid arch by two centers: one for the proximal part, the tympanohyal, appears before birth; the other, comprising the rest of the process, is named the stylohyal, and does not appear until after birth. The tympanic ring unites with the squama shortly before birth; the petromastoid part and squama join during the first year, and the tympanohyal portion of the styloid process about the same time

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The stylohyal does not unite with the rest of the bone until after

puberty Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a boy. ...

, and in some skulls never at all.

Postnatal development

Apart from size increase, the chief changes from birth through puberty in the temporal bone are as follows: # The tympanic ring extends outward and backward to form the tympanic part. This extension does not, however, take place at an equal rate all around the circumference of the ring, but occurs more at its anterior and posterior portions. As these outgrowths meet, they create a foramen in the floor of the meatus, the foramen of Huschke. This foramen is usually closed about the fifth year, but may persist throughout life. # The mandibular fossa is at first extremely shallow, and looks lateral and inferior; it deepens and directs more inferiorly over time. The part of the squama which forms the fossa lies at first below the level of the zygomatic process. As, the base of the skull thickens, this part of the squama is directed horizontal and inwards to contribute to the

middle cranial fossa The middle cranial fossa, deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull. It is separated from the posterior fossa by the clivus and the petrous crest. It is bounded in front by the pos ...

, and its surfaces look upward and downward; the attached portion of the zygomatic process everts and projects like a shelf at a right angle to the squama. # The mastoid portion is at first flat, with the stylomastoid foramen and rudimentary styloid immediately behind the tympanic ring. With air cell development, the outer part of the mastoid component grows anteroinferiorly to form the mastoid process, with the styloid and stylomastoid foramen now on the under surface. The descent of the foramen is accompanied by a requisite lengthening of the facial canal. # The downward and forward growth of the mastoid process also pushes forward the tympanic part; as a result, its portion that formed the original floor of the meatus, and contained the foramen of Huschke, rotates to become the anterior wall. # The ''fossa subarcuata'' is nearly effaced. File:Gray142.png, 1. Outer surface of petromastoid part. 2. Outer surface of tympanic ring. 3. Inner surface of squama. File:Gray143.png, Figure 7 : Temporal bone at birth. Outer aspect. File:Gray144.png, Figure 8 : Temporal bone at birth. Inner aspect.

Trauma

Temporal bone fractures were historically divided into three main categories, ''longitudinal'', in which the vertical axis of the fracture paralleled the petrous ridge, ''horizontal'', in which the axis of the fracture was perpendicular to the petrous ridge, and ''oblique'', a mixed type with both longitudinal and horizontal components. Horizontal fractures were thought to be associated with injuries to the

facial nerve The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste ...

, and longitudinal with injuries to the

middle ear ossicles The ossicles (also called auditory ossicles) are three bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditory ...

. More recently, delineation based on disruption of the otic capsule has been found as more reliable in predicting complications such as facial nerve injury, sensorineural hearing loss, intracerebral hemorrhage, and

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the ...

otorrhea Otitis media is a group of inflammatory diseases of the middle ear. One of the two main types is acute otitis media (AOM), an infection of rapid onset that usually presents with ear pain. In young children this may result in pulling at the ear, ...

Other animals

In many animals some of these parts stay separate through life: *

Squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral co ...

: the squama including the zygomatic process *

Tympanic bone The tympanic part of the temporal bone is a curved plate of bone lying below the squamous part of the temporal bone, in front of the mastoid process, and surrounding the external part of the ear canal. It originates as a separate bone (tympanic ...

: the tympanic part: this is derived from the angular bone of the reptilian lower jaw *

Periotic bone The periotic bone is the single bone that surrounds the inner ear of mammals. It is formed from the fusion of the prootic, epiotic, and opisthotic bones. References External links * http://www.encyclopedia.com/doc/1O8-perioticbone.html ...

: the petrous and mastoid parts * Two parts of the

hyoid The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical vertebra. ...

arch: the styloid process. In the dog these small bones are called tympanohyal (upper) and stylohyal (lower). In evolutionary terms, the temporal bone is derived from the fusion of many bones that are often separate in non-human mammals: * The

squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral co ...

bone, which is homologous with the squama, and forms the side of the cranium in many

bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilag ...

and

tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct theraps ...

s. Primitively, it is a flattened plate-like bone, but in many animals it is narrower in form, for example, where it forms the boundary between the two

temporal fenestra An infratemporal fenestra, also called the lateral temporal fenestra or simply temporal fenestra, is an opening in the skull behind the orbit in some animals. It is ventrally bordered by a zygomatic arch. An opening in front of the eye sockets ...

e of

diapsid Diapsids ("two arches") are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The group first appeared about three hundred million years a ...

reptiles. * The petrous and mastoid parts of the temporal bone, which derive from the

periotic bone The periotic bone is the single bone that surrounds the inner ear of mammals. It is formed from the fusion of the prootic, epiotic, and opisthotic bones. References External links * http://www.encyclopedia.com/doc/1O8-perioticbone.html ...

, formed from the fusion of a number of bones surrounding the ear of reptiles. The delicate structure of the

middle ear The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea (of the inner ear). The mammalian middle ear contains three ossicles, which transfer the vibrations of the eardrum into waves in the ...

, unique to mammals, is generally not protected in

marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...

s, but in

placental Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsup ...

s, it is usually enclosed within a bony sheath called the

auditory bulla The tympanic part of the temporal bone is a curved plate of bone lying below the squamous part of the temporal bone, in front of the mastoid process, and surrounding the external part of the ear canal. It originates as a separate bone (tympanic ...

. In many mammals this is a separate tympanic bone derived from the angular bone of the reptilian lower jaw, and, in some cases, it has an additional entotympanic bone. The auditory bulla is homologous with the tympanic part of the temporal bone. * Two parts of the

arch: the styloid process. In the dog the styloid process is represented by a series of 4 articulating bones, from top down tympanohyal, stylohyal, epihyal, ceratohyal; the first two represent the styloid process, and the ceratohyal represents the anterior horns of the hyoid bone and articulates with the basihyal which represents the body of the hyoid bone.

Etymology

Its exact etymology is unknown. It is thought to be from the Old French ''temporal'' meaning "earthly," which is directly from the Latin ''tempus'' meaning "time, proper time or season." Temporal bones are situated on the sides of the skull, where grey hairs usually appear early on. Or it may relate to the pulsations of the underlying superficial temporal artery, marking the time we have left here. There is also a probable connection with the Greek verb ''temnion'', to wound in battle. The skull is thin in this area and presents a vulnerable area for a blow from a battle axe. Another possible etymology is described at

Temple (anatomy) The temple is a latch where four skull bones fuse: the frontal, parietal, temporal, and sphenoid. It is located on the side of the head behind the eye between the forehead and the ear. The temporal muscle covers this area and is used during ...

Additional images

Image:Temporal bone lateral animation.gif, Position of temporal bone (green). Animation. Image:Left temporal bone close-up lateral animation2.gif, Shape of temporal bone (left). Image:Cranial bones en.svg, Cranial bones. File:Sphenoid and temporal bones 4.jpg, Sphenoid and temporal bones

Pathology

Glomus jugulare tumor: * A glomus jugulare tumor is a tumor of the part of the temporal bone in the skull that involves the middle and inner ear structures. This tumor can affect the ear, upper neck, base of the skull, and the surrounding blood vessels and nerves. * A glomus jugulare tumor grows in the temporal bone of the skull, in an area called the jugular foramen. The jugular foramen is also where the jugular vein and several important nerves exit the skull. * This area contains nerve fibers, called glomus bodies. Normally, these nerves respond to changes in body temperature or blood pressure. * These tumors most often occur later in life, around age 60 or 70, but they can appear at any age. The cause of a glomus jugulare tumor is unknown. In most cases, there are no known risk factors. Glomus tumors have been associated with changes (mutations) in a gene responsible for the enzyme succinate dehydrogenase (SDHD).

References

External links

* {{Authority control Bones of the head and neck