The temporal bone is a paired bone situated at the sides and base of the

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

, lateral to the

temporal lobe The temporal lobe is one of the four 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 is involved in pr ...

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. It is the largest site of Neuron, neural integration in the central nervous system, and plays ...

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

temples A temple (from the Latin ) is a place of worship, a building used for spiritual rituals and activities such as prayer and sacrifice. By convention, the specially built places of worship of some religions are commonly called "temples" in Engli ...

where four of the cranial bones fuse. Each temple is covered by a

temporal muscle In anatomy, the temporalis muscle, also known as the temporal muscle, is one of the muscles of mastication (chewing). It is a broad, fan-shaped convergent muscle on each side of the head that fills the temporal fossa, superior to the zygomatic ...

. The temporal bones house the structures of the

ear In vertebrates, an ear is the organ that enables hearing and (in mammals) body balance using the vestibular system. In humans, the ear is described as having three parts: the outer ear, the middle ear and the inner ear. The outer ear co ...

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 The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

traverse the temporal bone.

Structure

The temporal bone consists of four parts—the

squamous Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

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, t ...

, 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 (aka. malar) 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 ...

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 ), also called cheekbone or malar bone, is a paired irregular bone, situated at the upper and lateral part of the face and forming part of the lateral wall and floor of the orbit, of the temporal fos ...

. Posteroinferior to the squamous is the mastoid part. Fused with the squamous and mastoid parts and between the sphenoid and

occipital bone The occipital bone () is a neurocranium, cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone lies over the occipital lob ...

s 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: 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 of all kno ...

''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 m ...

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 posteri ...

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 The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the ...

and the

tympanic ossicle The ossicles (also called auditory ossicles) are three irregular bones in the middle ear of humans and other mammals, and are among the smallest bones in the human body. Although the term "ossicle" literally means "tiny bone" (from Latin ''ossicu ...

s: 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 Prenatal development () involves the development of the embryo and of the fetus during a viviparous animal's gestation. Prenatal development starts with fertilization, in the germinal stage of embryonic development, and continues in fetal de ...

ig. 6the 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 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, t ...

(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 from the middle ear. Its function is to transmit changes in pres ...

(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 ig. 7, 8 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 female, the testicles i ...

, 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 The mandibular fossa, also known as the glenoid fossa in some dental literature, is the depression in the temporal bone that articulates with the mandible. Structure In the temporal bone, the mandibular fossa is bounded anteriorly by the arti ...

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 is formed by the sphenoid bones, and the temporal bones. It lodges the temporal lobes, and the pituitary gland. It is deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull ...

, 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 subarcuate fossa 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, Temporal bone at birth. Outer aspect. File:Gray144.png, Temporal bone at birth. Inner aspect.

Clinical significance

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).

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 ta ...

, and longitudinal with injuries to the

middle ear ossicles The ossicles (also called auditory ossicles) are three irregular bones in the middle ear of humans and other mammals, and are among the smallest bones in the human body. Although the term "ossicle" literally means "tiny bone" (from Latin ''ossicu ...

. More recently, delineation based on disruption of the

otic capsule The bony labyrinth (also osseous labyrinth or otic capsule) is the rigid, bony outer wall of the inner ear in the temporal bone. It consists of three parts: the vestibule, semicircular canals, and cochlea. These are cavities hollowed out of the ...

has been found as more reliable in predicting complications such as facial nerve injury,

sensorineural hearing loss Sensorineural hearing loss (SNHL) is a type of hearing loss in which the root cause lies in the inner ear, sensory organ (cochlea and associated structures), or the vestibulocochlear nerve (Cranial nerves, cranial nerve VIII). SNHL accounts for a ...

intracerebral hemorrhage Intracerebral hemorrhage (ICH), also known as hemorrhagic stroke, is a sudden bleeding into Intraparenchymal hemorrhage, the tissues of the brain (i.e. the parenchyma), into its Intraventricular hemorrhage, ventricles, or into both. An ICH is ...

, and

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...

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 ancestra ...

: 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 The angular is a large bone in the lower jaw (mandible) of amphibians and reptiles (birds included), which is connected to all other lower jaw bones: the dentary (which is the entire lower jaw in mammals), the splenial, the suprangular, and the ...

of the reptilian lower jaw *

Periotic bone The periotic bone is the single bone that surrounds the inner ear of birds and mammals. It is formed from the fusion of the prootic, epiotic, and opisthotic bones, and in Cetacea forms a complex with the tympanic bone The tympanic part of the ...

: 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 verte ...

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 ancestra ...

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

bony fish Osteichthyes ( ; ), also known as osteichthyans or commonly referred to as the bony fish, is a Biodiversity, diverse clade of vertebrate animals that have endoskeletons primarily composed of bone tissue. They can be contrasted with the Chondricht ...

and

tetrapod A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetr ...

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 Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit (eye socket). These openings have historically been used to track the evolution and affinities of reptiles. Temporal fenestrae are commonly (al ...

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 earliest traditionally identified diapsids, the araeosc ...

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 birds and mammals. It is formed from the fusion of the prootic, epiotic, and opisthotic bones, and in Cetacea forms a complex with the tympanic bone The tympanic part of the ...

, 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 (malleus, incus, and stapes), which transfer the vibrations ...

, unique to mammals, is generally not protected in

marsupial Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a r ...

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 Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguished ...

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 b ...

. In many mammals this is a separate tympanic bone derived from the

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 four 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 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 verte ...

and articulates with the

basihyal The basihyal tooth plate is a specialized structure found in certain fish species. Basihyal tooth is the tooth that is attached to the basihyal tooth plate. It is part of the basihyal, a cartilage element located in the floor of the mouth that form ...

which represents the body of the hyoid bone.

Etymology

Its exact etymology is unknown. It is thought to be from the Old French meaning "earthly", which is directly from the Latin 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, also known as the pterion, is a latch where four skull bones intersect: 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 c ...

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

References

External links

* {{Authority control Otorhinolaryngology Human head and neck Skull bones Otology