Temporal bone

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The temporal bone is located at the sides and base of the skull, and laterally the temporal lobe of the cerebral cortex.

The temporal bone is coated by the side of the head known as the temple, and the house of the ear structure. Lower the seven cranial nerves and the major vessels to and from the brain across the temporal bone.

Video Temporal bone

Structure

The temporal bone consists of four parts - parts squamosa, mastoid, petrous and tympanic. The squamous portion is the largest and the most superior position relative to the rest of the bone. The zygomatic process is a curved long process that projects from the bottom of the squamous part and articulates with a zygomatic bone. Posteroinferior to the squamous is part of the mastoid. Combined with the squamous and mastoid sections and between the sphenoid and occipital bones located the petrous part, which is shaped like a pyramid. The tympanic part is relatively small and lies inferior to the squamous, anterior to the mastoid, and superior to the styloid process. Styloid, from the Greek stylos , is a phallic pillar directed inferiorly and anteromedially between the parotid glands and the internal jugular vein. The elongated or skewed styloid process can be generated from the calcification of the stylohyoid ligament in a condition known as Eagle Imadda .

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Development

The temporal bone hardened from eight centers, exclusive to the inner ear and tympanic ossicles: one for the skuama including the zygomatic process, one for the tympani part, four for the petrous and mastoid sections, and two for the styloid process.. Just before the end of prenatal development [Fig. 6] The temporal bone consists of three main parts:

1. Squash is hardened in the membrane of a single nucleus, which appears near the roots of the zygomatic process around the second month.
2. The petromastoid section is developed from four centers, which make their appearance in cartilage ear capsules around the fifth or sixth month. One (pro¶¶tic) appears in the eminentia arcuata environment, spreading in front of and above the internal auditory meatus and extending to the top of the bone; it forms part of the cochlea, vestibule, superior semicircular canal, and the medial wall of the tympanic cavity. The second (opisthotic) appears on a promontory on the medial wall of the tympanic cavity and encircles the cochleene fenestra; it forms the floor of the tympanic cavity and the vestibule, surrounds the carotid canal, invests the lateral and lower portions of the cochlea, and spreads medial under the internal auditory meatus. The third roof (pterotik) inside the tympanic cavity and antrum; while the fourth (epiotic) appears near the posterior semicircular canal and extends to form a mastoid process (Vralik).
3. The tympanic ring is an incomplete circle, in a groove that is a groove, a tympanic sulcus, for the peripheral attachment of the eardrum (tympanic membrane). This ring expands to form the tympanic part, and is bound in the membrane of a single center that appears around the third month. The styloid process is developed from the proximal portion of the cartilage of the branchial or hyoid arches by two centers: one for the proximal, tympanohyal, arises before birth; the other, composed of the rest of the process, is named stylohyal, and does not appear until after birth. The tympanic ring united with squam just before birth; parts of petromastoid and squam joined during the first year, and tympanohyal parts of the styloid process around the same time [Fig. 7, 8]. Stylohyal does not unite with the rest of the bones until after puberty, and in some skulls is never at all.

Postnatal development

Regardless of the increase in size, head changes from birth to puberty in the temporal bone are as follows:

1. The tympanic ring extends outward and backward to form a tympanic member. However, this extension does not take place at the same level around the ring circle, but occurs more in the anterior and posterior parts. As this growth meets, they create the foramen on the meatus floor, foramen Huschke. The foramen is usually closed around the fifth year, but it can last a lifetime.
2. The mandibular fossa is initially very shallow, and looks lateral and inferior; it deepens and steers more inferior over time. The part of the skuama that forms the fossa lies first below the level of the zygomatic process. Like, the base of the skull thickens, part of the skuama is directed horizontally and inward to contribute to the middle cranial fossa, and its surface is seen up and down; the attached portion of the zygomatic process gives evert and projects like racks at right angles to the skuama.
3. The mastoid part is initially flat, with stylomastoid foramen and sterile styloid just behind the tympanic ring. With the development of air cells, the outer part of the mastoid component grows anteroinferior to form a mastoid process, with stylomastoid foramen now foramen beneath the surface. The fall of the foramen is accompanied by the elongation of the facial canal.
4. Downward and forward growth of the mastoid process also pushes forward the tympanic part; as a result, the part that forms the original floor of the meatus, and contains the foramen Huschke, rotates into the anterior wall.
5. The fossa subarcuata is almost deleted.

Maps Temporal bone

Trauma

Temporal bone fractures have historically been divided into three main categories, longitudinal, where the vertical axis of the fracture aligns the petrous ridge, horizontally, where the fracture axis is perpendicular to the petrous ridge, and italics , mixed types with longitudinal and horizontal components. A horizontal fracture is thought to be associated with an injury to the facial nerve, and is lengthened by injury to the middle ear ossicles. More recently, delineation based on the disorders of otic capsules has been found to be more reliable in predicting complications such as facial nerve injury, sensorineural hearing loss, intracerebral hemorrhage, and cerebrospinal fluid otorrhea.

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Other animals

In many animals some of these parts remain apart for life:

• Squamosal: skuama including the zygomatic process
• Tympanic bone: the tympanic part: it comes from the reptile jaw bone angle
• The periotic bone: the petrous and mastoid parts
• Two parts of the hyoid arch: the styloid process. In dogs, these small bones are called tympanohyal (top) and stylohyal (inferior).

In evolutionary terms, the temporal bone comes from the fusion of many bones that are often separated in non-human mammals:

• Squamosal bone, which is homologous to squam, and forms the side of the skull in many bony fish and tetrapods. Primitively, it is a flat plate-like bone, but in many animals its shape is narrower, for example, where it forms the boundary between the two temporal reptile diapids fenestrae.
• The part of the petrous and mastoid of the temporal bone, derived from the periotic bone, is formed from the fusion of a number of bones around the ear of the reptile. The delicate middle ear structure, unique to mammals, is generally not protected on marsupials, but on the placenta, usually covered in a layer of bone called the auditory bull. In many mammals, this is a separate split bone of bone derived from the reptile's lower jaw bone, and, in some cases, it has an additional entotympanic bone . The hearing bull is homologous to the tympanic part of the temporal bone.
• Two parts of the hyoid arch: the styloid process. In dogs, the styloid process is represented by a series of 4 articulation bones, from top down tympanohyal, stylohyal, epihyal, ceratohyal; the first two representing the styloid process, and ceratohyal representing the anterior horn of the hyoid bone and articulate with the basihyal representing the body of the hyoid bone.

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Etymology

The exact etymology is unknown. It is presumably derived from the ancient French temporal which means "worldly", which is directly derived from the Latin tempus meaning "the right time, time or season." The temporal bone is located on the side of the skull, where gray hair usually appears early on. Or it may be related to the underlying superficial temporal pulsation, marking the time left here. There is also the possibility of a relationship with the Greek verb temnion , for wounds in battle. The skull is thin in this area and presents a vulnerable area for blows from the battle ax. Another possible etymology is described in the Temple (anatomy).

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Additional images

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Pathology

Globus Tumor jugulare:

• The jugulare glomerus tumor is a tumor of the temporal bone in the skull involving the inner and middle ear structures. These tumors can affect the ears, upper neck, the base of the skull, and the surrounding blood vessels and nerves.
• The jugulare glomus tumor grows on the skull's temporal bone, in an area called the jugular foramen. The jugular foramen is also where the jugular vein and some important nerves come out of the skull.
• This area contains nerve fibers, called glomus bodies. Usually, these nerves respond to changes in body temperature or blood pressure.
• These tumors most commonly occur later, around the age of 60 or 70 years, but they can appear at any age. The cause of jugular glomerus tumor is unknown. In many cases, no known risk factors exist. Glomus tumors have been associated with changes (mutations) in genes responsible for the enzyme succinic dehydrogenase (SDHD).

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See also

• Chorda tympani
• Cholesteatoma
• Koerner septum
• Temporal muscle
• Temporomandibular joint

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References

This article combines text in the public domain of page 138 of the 20th edition of Gray's Anatomy (1918)

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External links

• "Anatomical diagram: 34256.000-1". Roche Lexicon - illustrated navigator . Elsevier. Archived from the original in 2014-01-01.

Source of the article : Wikipedia