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The temporal bones are situated at the sides and base of the
skull The skull is a bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North A ...

skull
, and lateral to the
temporal lobe The temporal lobe is one of the four major lobes 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 m ...

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% consisting of a ...
. The temporal bones are overlaid by the sides of the head known as the
temples A temple (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of t ...
, and house the structures of the
ear The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts—the outer ear The outer ear, external ear, or auris externa is the external part of the ear, which consists ...

ear
s. The lower seven
cranial nerves Cranial nerves are the nerve A nerve is an enclosed, cable-like bundle of fibers (called axon An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, ...
and the major vessels to and from the
brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tis ...

brain
traverse the temporal bone.


Structure

The temporal bone consists of four parts— the
squamous Epithelium is one of the four basic types of animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as ...
,
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 Foramen, openings for blood vessels. From its bo ...
, 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 A process is a series or set of Action (philosophy), activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and m ...
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 skull is a bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the skeleton in most vertebrate animals. Bones protect the various organs of the body, produce red blood cell, red and ...

zygomatic bone
. Posteroinferior to the squamous is the mastoid part. Fused with the squamous and mastoid parts and between the
sphenoid
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 Trapezoid, trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occi ...

occipital bone
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#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
''stylos'', is a phallic shaped pillar directed inferiorly and anteromedially between the
parotid gland The parotid gland is a major salivary gland The salivary glands in mammals are exocrine glands that produce saliva through a system of Duct (anatomy), ducts. Humans have three paired major salivary glands (Parotid gland, parotid, Submandibular ...
and
internal jugular vein The internal jugular vein is a paired jugular vein The jugular veins are vein Veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary vei ...
. An elongated or deviated styloid process can result from
calcification Calcification is the accumulation of calcium Calcium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, ...
of the
stylohyoid ligament The stylohyoid ligament is a ligament that connects the hyoid bone to the temporal styloid process (of the temporal bone of the skull). Structure The stylohyoid ligament connects the Hyoid bone, lesser horn of hyoid bone to the Temporal styloid ...
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 T ...

Eagle syndrome
''.


Borders


Development

The temporal bone is
ossified Ossification (or osteogenesis) in bone remodeling Bone remodeling (or bone metabolism) is a lifelong process where mature bone tissue A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar ce ...
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 The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts—the outer ear T ...
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 Prenatal development () includes the development of the embryo and of the foetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo An embryo is the early stage of ...

prenatal development
ig. 6 IG, Ig, or ig may refer to: Companies * IG Farben Interessengemeinschaft Farbenindustrie AG (), commonly known as IG Farben (German for "IG Colors"), was a German chemical and pharmaceutical conglomerate Conglomerate or conglomeration may ref ...
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 The ectotympanic, or tympanicum, is a bony ring in the tympanic part of the temporal bone that holds the eardrum, or tympanic membrane. Its position and attachment to the skull vary within mammals, and particularly primates, and can be either insi ...
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 Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, ...
(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 Biologically, a child (plural children) is a human Humans (''Homo sapiens'') are the most abundant and widespread species In biology Biology is the natur ...

puberty
, 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 The ectotympanic, or tympanicum, is a bony ring in the tympanic part of the temporal bone that holds the eardrum, or tympanic membrane. Its position and attachment to the skull vary within mammals, and particularly primates, and can be either insi ...
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 The anterior cranial fossa is a depression in the floor of the cranial base which houses the projecting frontal lobes of the brain. It is formed by the orbital plates of the fronta ...
, 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 (the labyrinthine segment) is the seventh Cranial nerves, cranial nerve, or simply CN VII. It emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensation ...

facial nerve
, and longitudinal with injuries to the middle ear ossicles. 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 Inner Ear (established in 2007 in Bodø, Norway) is a Norwegian record label initiated and led by the brothers and jazz musicians Tore Joha ...
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 Hearing loss is a partial or total inability to hear Hearing, or auditory perception, is the ability to perceive Sound, sounds by detecting Vibration, vibrations, changes in ...
,
intracerebral hemorrhage Intracerebral hemorrhage (ICH), also known as cerebral bleed, intraparenchymal bleed, and hemorrhagic stroke, or haemorrhagic stroke, is a sudden bleeding into the tissues of the brain, into its ventricles, or into both. It is one kind of bleed ...
, and
cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid Body fluids, bodily fluids, or biofluids are liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochor ...
otorrhea Otitis media is a group of inflammatory Inflammatory may refer to: * Inflammation, a biological response to harmful stimuli * The word ''inflammatory'' is also used to refer literally to fire and flammability, and figuratively in relation to com ...
.


Other animals

In many animals some of these parts stay separate through life: *
Squamosal The squamosal is a skull The skull is a bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geome ...
: 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 b ...
: the tympanic part: this is derived from the
angular bone The angular is a large bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in Nort ...
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 S ...
: the petrous and mastoid parts * Two parts of the
hyoid The hyoid bone (lingual bone or tongue-bone) () is a horseshoe A horseshoe is a fabricated product, normally made of metal A metal (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ε ...
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 The skull is a bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geome ...
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 taxonomic Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may al ...

bony fish
and
tetrapod Tetrapods (; ) are four-limbed animals constituting the superclass Tetrapoda (). It includes extant Extant is the opposite of the word extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a sp ...
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 {{Unreferenced, date=January 2009 An infratemporal fenestra, also called the lateral temporal fenestra or simply temporal fenestra, is an opening in the skull behind the orbit In celestial mechanics, an orbit is the curved trajectory of an p ...
e of
diapsid Diapsids ("two arches") are a group of amniote tetrapods that developed two holes (temporal fenestra) in each side of their skulls about 300 million years ago during the late Carboniferous period. The diapsids are extremely diverse, and include all ...

diapsid
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 S ...
, 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 The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts—the outer ear The outer ear, external ear, or auris externa is t ...

middle ear
, unique to mammals, is generally not protected in
marsupial Marsupials are any members of the mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ' ...
s, but in
placental The infraclass In biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, mole ...
s, it is usually enclosed within a bony sheath called the
auditory bulla The tympanic part of the temporal bone The temporal bones are situated at the sides and base of the skull The skull is a bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells th ...
. In many mammals this is a separate tympanic bone derived from the
angular bone The angular is a large bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in Nort ...
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
hyoid The hyoid bone (lingual bone or tongue-bone) () is a horseshoe A horseshoe is a fabricated product, normally made of metal A metal (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ε ...
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 The hyoid bone (lingual bone or tongue-bone) () is a horseshoe A horseshoe is a fabricated product, normally made of metal A metal (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ε ...
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 juncture where four skull bones fuse together: the frontal Front may refer to: Arts, entertainment, and media Films * The Front (1943 film), ''The Front'' (1943 film), a 1943 Soviet drama film * ''The Front'', 1976 film Music ...
.


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).


See also

*
Chorda tympani The chorda tympani is a branch of the facial nerve The facial nerve (the labyrinthine segment) is the seventh cranial nerve Cranial nerves are the nerve A nerve is an enclosed, cable-like bundle of nerve fibers called axon An axon (f ...
*
Cholesteatoma Cholesteatoma is a destructive and expanding growth consisting of keratinizing squamous epithelium in the middle ear and/or mastoid process. Cholesteatomas are not cancerous as the name may suggest, but can cause significant problems because of the ...
* Koerner's septum *
Temporal muscle In anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of concerned with the study of the structure of s and their parts. Anatomy is a branch of natural science which deals with the structural organization of living things. It i ...

Temporal muscle
*
Temporomandibular joint In anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science which deals with the structural organization of ...

Temporomandibular joint


References


External links

* {{Authority control Bones of the head and neck