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Encyclopedia > Skull
A closeup of the front of a human skull.
A closeup of the front of a human skull.

The skull is a bony structure found in many animals which serves as the general framework for the head. The skull supports the structures of the face and protects the head against injury. The skull is the bony structure in the head of a craniate. ... Look up cranium in Wiktionary, the free dictionary. ... Image File history File links Metadata Size of this preview: 399 × 599 pixelsFull resolution (853 × 1280 pixel, file size: 124 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Metadata Size of this preview: 399 × 599 pixelsFull resolution (853 × 1280 pixel, file size: 124 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... This article is about the skeletal organs. ... For other uses, see Animal (disambiguation). ... For other uses of the word head, see head (disambiguation). ... For other uses, see Face (disambiguation). ... For other uses, see Head (disambiguation). ...


The skull can be subdivided into two parts: the cranium and the mandible. A skull that is missing a mandible is only a cranium; this is the source of a very commonly made error in terminology. Those animals having skulls are called craniates. Classes Hyperotreti Vertebrata Craniata is a type of chordate animal group that contains vertebrates (vertebrata) and hagfish (Hyperotreti). ...


Protection of the brain is only one part of the function of a bony skull. For example, a fixed distance between the eyes is essential for stereoscopic vision, and a fixed position for the ears helps the brain to use auditory cues to judge direction and distance of sounds. In some animals, the skull also has a defensive function (e.g. horned ungulates); the frontal bone is where horns are mounted. Binocular vision (also referred to as stereoscopic vision) is a type of visual system common in many kinds of animals where both the eyes produce only a single image in the brain. ... Ungulates (meaning roughly hoofed or hoofed animal) make up several orders of mammals, of which six survive: Artiodactyla: even-toed ungulates, cattle, sheep, goats, pigs, antelope, and many others Cetacea: whales and dolphins (which evolved from hoofed land animals) Perissodactyla: odd-toed ungulates such as horses and rhinos Proboscidea: elephants... The frontal bone (os frontale, TA: A02. ...

Contents

Human skulls

Main article: Human skull
Human skull (front)
Human skull (front)
Human skull (side)
Human skull (side)

In humans, the adult skull is normally made up of 22 bones. Except for the mandible, all of the bones of the skull are joined together by sutures, rigid articulations permitting very little movement. Eight bones form the neurotesticle (braincase), a protective vault surrounding the brain. Fourteen bones form the spleenchnocranium, the bones supporting the face. Encased within the temporal bones are the six ear ossicles of the middle ears, though these are not part of the skull. The hyoid bone, supporting the tongue, is usually not considered as part of the skull either, as it does not articulate with any other bones. In humans, the adult skull is normally made up of 22 bones. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... A miserable stubborn cantankerous old mans, whos actually quite good humoured & an enjoyable compadre to play online alongside if you catch him on a good day. ... The mandible (from Latin mandibÅ­la, jawbone) or inferior maxillary bone is, together with the maxilla, the largest and strongest bone of the face. ... Side view of the skull. ... The cranial vault is the space in the skull within the neurocranium. ... The temporal bones (os temporales) are situated at the sides and base of the skull. ... The ossicles (also called auditory ossicles) are the three smallest bones in the human body. ... The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. ... The hyoid bone (Os Hyoideum; Lingual Bone) is a bone in the human neck, not articulated to any other bone; it is supported by the muscles of the neck and in turn supports the root of the tongue. ... For other uses, see Tongue (disambiguation). ...


The skull contains the sinus cavities, which are air-filled cavities lined with respiratory epithelium, which also lines the large airways. The exact functions of the sinuses are unclear; they may contribute to lessening the weight of the skull with a minimal reduction in strength,or they may be important in improving the resonance of the voice. In some animals, such as the elephant, the sinuses are extensive. The elephant skull needs to be very large, to form an attachment for muscles of the neck and trunk, but is also unexpectedly light; the comparatively small brain-case is surrounded by large sinuses which reduce the weight. The meninges are the three layers, or membranes, which surround the structures of the nervous system. They are known as the dura mater, the arachnoid mater and the pia mater. Other than being classified together, they have little in common with each other. The paranasal sinuses are eight (four pairs) air-filled spaces, or sinuses, within the bones of the skull and face. ... Respiratory epithelium is another name for ciliated pseudostratified columnar epithelium with goblet cells. ... Genera and Species Loxodonta Loxodonta cyclotis Loxodonta africana Elephas Elephas maximus Elephas antiquus † Elephas beyeri † Elephas celebensis † Elephas cypriotes † Elephas ekorensis † Elephas falconeri † Elephas iolensis † Elephas planifrons † Elephas platycephalus † Elephas recki † Stegodon † Mammuthus † Elephantidae (the elephants) is a family of pachyderm, and the only remaining family in the order Proboscidea... The meninges (singular meninx) are the system of membranes that envelop the central nervous system. ... The Human Nervous System. ... The dura mater (from the Latin hard mother), or pachymeninx, is the tough and inflexible outermost of the three layers of the meninges surrounding the brain. ... The Arachnoid mater is one of the three layers of the meninges, interposed between the dura mater and the pia mater and separated from the pia mater by the subarachnoid space. ... [www. ...


In humans, the anatomical position for the skull is the Frankfurt plane, where the lower margins of the orbits and the upper borders of the ear canals are all in a horizontal plane. This is the position where the subject is standing and looking directly forward. For comparison, the skulls of other species, notably primates and hominids, may sometimes be studied in the Frankfurt plane. However, this does not always equate to a natural posture in life. The anatomical planes The anatomical position is a schematic convention for describing the relative morphology of the human body. ... The Frankfurt plane (also called the auriculo-orbital plane) was established at the World Congress on Anthropology in Frankfurt, Germany in 1884, and decreed as the anatomical position of the human skull. ... In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. ... The ear canal (external auditory meatus, external acoustic meatus), is a tube running from the outer ear to the middle ear. ... For the ecclesiastical use of this term, see primate (religion) Families 13, See classification A primate is any member of the biological order Primates, the group that contains all lemurs, monkeys, and apes, including humans. ... Genera Subfamily Ponginae Pongo - Orangutans Gigantopithecus (extinct) Sivapithecus (extinct) Subfamily Homininae Gorilla - Gorillas Pan - Chimpanzees Homo - Humans Paranthropus (extinct) Australopithecus (extinct) Sahelanthropus (extinct) Ardipithecus (extinct) Kenyanthropus (extinct) Pierolapithecus (extinct) (tentative) The Hominids (Hominidae) are a biological family which includes humans, extinct species of humanlike creatures and the other great apes...


Possible types of skull fractures

Main articles: Skull fracture, tripod fracture, and LeFort fracture

A skull fracture is a break in one or more of the bones in the skull caused by a head injury. ... The tripod fracture, also called the zygomaticomaxillary complex, is composed of a set of fractures including the lateral orbital wall, inferior orbital floor, and the zygomatic arch. ... LeFort fractures (also spelled as Le Fort fractures) are types of facial fractures that are classic in trauma. ...

Animal skulls

Temporal Fenestra

This Tyrannosaurus skull shows it was a diapsid
This Tyrannosaurus skull shows it was a diapsid

The temporal fenestra are anatomical features of the amniote skull, characterised by bilaterally symmetrical holes (fenestrae) in the temporal bone. Depending on the lineage of a given animal, two, one, or no pairs of temporal fenestrae may be present, above or below the postorbital and squamosal bones. The upper temporal fenestrae are also known as the supratemporal fenestrae, and the lower temporal fenestrae are also known as the infratemporal fenestrae. The presence and morphology of the temporal fenestra is critical for taxonomic classification of the synapsids, of which mammals are part. Download high resolution version (875x589, 547 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (875x589, 547 KB) Wikipedia does not have an article with this exact name. ... Species T. rex (type) Osborn, 1905 Synonyms Manospondylus Cope, 1892 Dynamosaurus Osborn, 1905  ?Nanotyrannus Bakker, Williams & Currie, 1988 Stygivenator Olshevsky, 1995 Dinotyrannus Olshevsky, 1995 Tyrannosaurus (pronounced IPA: , meaning tyrant lizard) is a genus of theropod dinosaur. ... Groups See Text Diapsids (two arches) are a group of tetrapod animals that developed two holes (temporal fenestra) in each side of their skulls, about 300 million years ago during the late Carboniferous period. ... Fenestrae (singular: fenestra) are small pores in epithelial cells to allow for rapid exchange of molecules between blood vessels and surrounding tissue. ... Extant subgroups Synapsida     Mammalia (mammals) Sauropsida    Anapsida        Testudines (turtles)    Diapsida        Lepidosauria           Squamata (lizards and snakes)           Sphenodontida (tuatara)        Archosauria           Crocodilia (crocodiles and alligators)           Aves (birds) The amniotes are a group of vertebrates, comprising the mammals, birds, and various other groups collectively referred to as reptiles. ... The postorbital is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. ... The squamosal is a bone of the head of higher vertebrates. ...


Physiological speculation associates it with a rise in metabolic rates and an increase in jaw musculature. The earlier amniotes of the Carboniferous did not have temporal fenestrae but the more advanced sauropsids and synapsids did. As time progressed, sauropsids' and synapsids' temporal fenestrae became more modified and larger to make stronger bites and more jaw muscles. Dinosaurs, which are sauropsids, have large advanced openings and their descendants, the birds, have temporal fenestrae which have been modified. Mammals, which are synapsids, possess no fenestral openings in the skull, as the trait has been modified. They do, though, still have the temporal orbit (which resembles an opening) and the temporal muscles. It is a hole in the head and is situated to the rear of the orbit behind the eye.


Classification

Humans, despite having lost their fenestrae, are synapsids
Humans, despite having lost their fenestrae, are synapsids

There are four types of amniote skull, classified by the number and location of their fenestra. These are: Image File history File links Gray188. ... Image File history File links Gray188. ... Are small pores in epithelial cells to allow for rapid exchange of molecules between blood vessels and surrounding tissue. ... Orders & Suborders Order Pelycosauria * Suborder Caseasauria Suborder Eupelycosauria * Order Therapsida * Suborder Biarmosuchia Suborder Dinocephalia Suborder Anomodontia Suborder Gorgonopsia Suborder Therocephalia Suborder Cynodontia * For complete phylogeny, see text. ...

  • Anapsida - no openings
  • Synapsida - one low opening (beneath the postorbital and squamosal bones)
  • Euryapsida - one high opening (above the postorbital and squamosal bones); euryapsids actually evolved from a diapsid configuration, losing their lower temporal fenestra.
  • Diapsida - two openings

Evolutionary, they are related like so: Orders Testudines (Turtles, tortoises & terrapins) Mesosauria - extinct Millerettidae - extinct Nyctiphruretidae - extinct Pareiasauridae - extinct Procolophonidae - extinct Captorhinida - extinct For the extinct fish, see Anaspid. ... Orders & Suborders Order Pelycosauria * Suborder Caseasauria Suborder Eupelycosauria * Order Therapsida * Suborder Biarmosuchia Suborder Dinocephalia Suborder Anomodontia Suborder Gorgonopsia Suborder Therocephalia Suborder Cynodontia * For complete phylogeny, see text. ... Euryapsida are a group of tetrapod animals that are distinguished by a single opening behind the orbit (temporal fenestra). ... Groups See Text Diapsids (two arches) are a group of tetrapod animals that developed two holes (temporal fenestra) in each side of their skulls, about 300 million years ago during the late Carboniferous period. ...

See also

This article is about the skeletal organs. ... In sciences dealing with the anatomy of animals, precise anatomical terms of location are necessary for a variety of reasons. ... An MRI scan of the head. ... Phrenology (from Greek: φρήν, phrēn, mind; and λόγος, logos, knowledge) is a theory which claims to be able to determine character, personality traits and criminality on the basis of the shape of the head (i. ... This article or section is not written in the formal tone expected of an encyclopedia article. ...

References

  • White, T.D. 1991. Human osteology. Academic Press, Inc. San Diego, CA.

External links

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Skulls
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  Results from FactBites:
 
BBC Science & Nature - Human Body and Mind - Skeleton Layer (418 words)
Your skull is made up of two sets of bones - the bones of your face and the bones of your cranium, which make up your forehead and the back of your head.
And the back of your skull is formed by your occipital bone which has an opening in it where your spinal cord connects to your brain.
This means that the skull can flex and deform during birth, making it easier to deliver a baby through the narrow birth canal.
  More results at FactBites »

 
 

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