Skull

The skull is a bony structure that forms the head in vertebrates. It supports the structures of the face and provides a protective cavity for the brain.[1] The skull is composed of two parts: the cranium and the mandible. In humans, these two parts are the neurocranium and the viscerocranium or facial skeleton that includes the mandible as its largest bone. The skull forms the anterior most portion of the skeleton and is a product of cephalisation—housing the brain, and several sensory structures such as the eyes, ears, nose, and mouth.[2] In humans these sensory structures are part of the facial skeleton.

Functions of the skull include protection of the brain, fixing the distance between the eyes to allow stereoscopic vision, and fixing the position of the ears to enable sound localisation of the direction and distance of sounds. In some animals such as horned ungulates, the skull also has a defensive function by providing the mount (on the frontal bone) for the horns.

The English word "skull" is probably derived from Old Norse "skulle", while the Latin word cranium comes from the Greek root κρανίον (kranion).

The skull is made up of a number of fused flat bones, and contains many foramina, fossae, processes, and several cavities or sinuses. In zoology there are openings in the skull called fenestrae.

Skull
VolRenderShearWarp
Details
SystemSkeletal system
Identifiers
MeSHD012886
TAA02.1.00.001
FMA46565
Anatomical terminology

Structure

For details and the constituent bones, see Neurocranium and Facial skeleton
Lateral head skull
Skull in situ
621 Anatomy of a Flat Bone
Anatomy of a flat bone - the periosteum of the neurocranium is known as the pericranium
Sobo 1909 38
Human skull from the front
Human skull side bones
Side bones of skull

The human skull is the bony structure that forms the head in the human skeleton. It supports the structures of the face and forms a cavity for the brain. Like the skulls of other vertebrates, it protects the brain from injury.

The skull consists of three parts, of different embryological origin—the neurocranium, the sutures, and the facial skeleton (also called the membraneous viscerocranium). The neurocranium (or braincase) forms the protective cranial cavity that surrounds and houses the brain and brainstem. The upper areas of the cranial bones form the calvaria (skullcap). The membranous viscerocranium includes the mandible.

The sutures are fairly rigid joint between bones of the neurocranium.

The facial skeleton is formed by the bones supporting the face

Bones

Except for the mandible, all of the bones of the skull are joined together by suturessynarthrodial (immovable) joints formed by bony ossification, with Sharpey's fibres permitting some flexibility. Sometimes there can be extra bone pieces within the suture known as wormian bones or sutural bones. Most commonly these are found in the course of the lambdoid suture.

The human skull is generally considered to consist of twenty-two bones—eight cranial bones and fourteen facial skeleton bones. In the neurocranium these are the occipital bone, two temporal bones, two parietal bones, the sphenoid, ethmoid and frontal bones.

The bones of the facial skeleton (14) are the vomer, two inferior nasal conchae, two nasal bones, two maxilla, the mandible, two palatine bones, two zygomatic bones, and two lacrimal bones. Some sources count a paired bone as one, or the maxilla as having two bones (as its parts); some sources include the hyoid bone or the three ossicles of the middle ear but the overall general consensus of the number of bones in the human skull is the stated twenty-two.

Some of these bones—the occipital, parietal, frontal, in the neurocranium, and the nasal, lacrimal, and vomer, in the facial skeleton are flat bones.

Cavities and foramina

3d CT scan animation
CT scan of a human skull in 3D

The skull also contains sinuses, air-filled cavities known as paranasal sinuses, and numerous foramina. The sinuses are lined with respiratory epithelium. Their known functions are the lessening of the weight of the skull, the aiding of resonance to the voice and the warming and moistening of the air drawn into the nasal cavity.

The foramina are openings in the skull. The largest of these is the foramen magnum that allows the passage of the spinal cord as well as nerves and blood vessels.

Processes

The many processes of the skull include the mastoid process and the zygomatic processes.

Development

Sobo 1909 104
Skull of a new-born child from the side

The skull is a complex structure; its bones are formed both by intramembranous and endochondral ossification. The skull roof bones, comprising the bones of the facial skeleton and the sides and roof of the neurocranium, are dermal bones formed by intramembranous ossification, though the temporal bones are formed by endochondral ossification. The endocranium, the bones supporting the brain (the occipital, sphenoid, and ethmoid) are largely formed by endochondral ossification. Thus frontal and parietal bones are purely membranous.[3] The geometry of the skull base and its fossae, the anterior, middle and posterior cranial fossae changes rapidly. The anterior cranial fossa changes especially during the first trimester of pregnancy and skull defects can often develop during this time.[4]

At birth, the human skull is made up of 44 separate bony elements. During development, many of these bony elements gradually fuse together into solid bone (for example, the frontal bone). The bones of the roof of the skull are initially separated by regions of dense connective tissue called fontanelles. There are six fontanelles: one anterior (or frontal), one posterior (or occipital), two sphenoid (or anterolateral), and two mastoid (or posterolateral). At birth these regions are fibrous and moveable, necessary for birth and later growth. This growth can put a large amount of tension on the "obstetrical hinge", which is where the squamous and lateral parts of the occipital bone meet. A possible complication of this tension is rupture of the great cerebral vein. As growth and ossification progress, the connective tissue of the fontanelles is invaded and replaced by bone creating sutures. The five sutures are the two squamous sutures, one coronal, one lambdoid, and one sagittal suture. The posterior fontanelle usually closes by eight weeks, but the anterior fontanel can remain open up to eighteen months. The anterior fontanelle is located at the junction of the frontal and parietal bones; it is a "soft spot" on a baby's forehead. Careful observation will show that you can count a baby's heart rate by observing the pulse pulsing softly through the anterior fontanelle.

The skull in the neonate is large in proportion to other parts of the body. The facial skeleton is one seventh of the size of the calvaria. (In the adult it is half the size). The base of the skull is short and narrow, though the inner ear is almost adult size.[5]

Clinical significance

Craniosynostosis is a condition in which one or more of the fibrous sutures in an infant skull prematurely fuses,[6] and changes the growth pattern of the skull.[7] Because the skull cannot expand perpendicular to the fused suture, it grows more in the parallel direction.[7] Sometimes the resulting growth pattern provides the necessary space for the growing brain, but results in an abnormal head shape and abnormal facial features.[7] In cases in which the compensation does not effectively provide enough space for the growing brain, craniosynostosis results in increased intracranial pressure leading possibly to visual impairment, sleeping impairment, eating difficulties, or an impairment of mental development.[8]

A copper beaten skull is a phenomenon wherein intense intracranial pressure disfigures the internal surface of the skull.[9] The name comes from the fact that the inner skull has the appearance of having been beaten with a ball-peen hammer, such as is often used by coppersmiths. The condition is most common in children.

Injuries and treatment

Injuries to the brain can be life-threatening. Normally the skull protects the brain from damage through its hard unyieldingness; the skull is one of the least deformable structures found in nature with it needing the force of about 1 ton to reduce the diameter of the skull by 1 cm.[10] In some cases, however, of head injury, there can be raised intracranial pressure through mechanisms such as a subdural haematoma. In these cases the raised intracranial pressure can cause herniation of the brain out of the foramen magnum ("coning") because there is no space for the brain to expand; this can result in significant brain damage or death unless an urgent operation is performed to relieve the pressure. This is why patients with concussion must be watched extremely carefully.

Dating back to Neolithic times, a skull operation called trepanning was sometimes performed. This involved drilling a burr hole in the cranium. Examination of skulls from this period reveals that the patients sometimes survived for many years afterward. It seems likely that trepanning was also performed purely for ritualistic or religious reasons. Nowadays this procedure is still used but is normally called a craniectomy.

In March 2013, for the first time in the U.S., researchers replaced a large percentage of a patient's skull with a precision, 3D-printed polymer implant.[11] About 9 months later, the first complete cranium replacement with a 3D-printed plastic insert was performed on a Dutch woman. She had been suffering from hyperostosis, which increased the thickness of her skull and compressed her brain.[12]

A study conducted in 2018 by the researchers of Harvard Medical School in Boston, funded by National Institutes of Health (NIH) suggested that instead of travelling via blood, there are "tiny channels" in the skull through which the immune cells combined with the bone marrow reach the areas of inflammation after an injury to the brain tissues.[13]

Transgender procedures

Surgical alteration of sexually dimorphic skull features may be carried out as a part of facial feminization surgery, a set of reconstructive surgical procedures that can alter male facial features to bring them closer in shape and size to typical female facial features.[14][15] These procedures can be an important part of the treatment of transgender people for gender dysphoria.[16][17]

Society and culture

SSACRAM 116
A skull is the symbol of penance, Silk embroidery (17th century)

Artificial cranial deformation is a largely historical practice of some cultures. Cords and wooden boards would be used to apply pressure to an infant's skull and alter its shape, sometimes quite significantly. This procedure would begin just after birth and would be carried on for several years.

Osteology

Like the face, the skull and teeth can also indicate a person's life history and origin. Forensic scientists and archaeologists use metric and nonmetric traits to estimate what the bearer of the skull looked like. When a significant amount of bones are found, such as at Spitalfields in the UK and Jōmon shell mounds in Japan, osteologists can use traits, such as the proportions of length, height and width, to know the relationships of the population of the study with other living or extinct populations.

The German physician Franz Joseph Gall in around 1800 formulated the theory of phrenology, which attempted to show that specific features of the skull are associated with certain personality traits or intellectual capabilities of its owner. His theory is now considered to be pseudoscientific.

Sexual dimorphism

In the mid-nineteenth century, anthropologists found it crucial to distinguish between male and female skulls. An anthropologist of the time, James McGrigor Allan, argued that the female brain was similar to that of an animal.[18] This allowed anthropologists to declare that women were in fact more emotional and less rational than men. McGrigor then concluded that women's brains were more analogous to infants, thus deeming them inferior at the time.[18] To further these claims of female inferiority and silence the feminists of the time, other anthropologists joined in on the studies of the female skull. These cranial measurements are the basis of what is known as craniology. These cranial measurements were also used to draw a connection between women and black people.[18]

Research has shown that while in early life there is little difference between male and female skulls, in adulthood male skulls tend to be larger and more robust than female skulls, which are lighter and smaller, with a cranial capacity about 10 percent less than that of the male.[19] However, later studies show that women's skulls are slightly thicker and thus men may be more susceptible to head injury than women.[20][21]

Male skulls can have more prominent supraorbital ridges, a more prominent glabella, and more prominent temporal lines. Female skulls generally have rounder orbits, and narrower jaws. Male skulls on average have larger, broader palates, squarer orbits, larger mastoid processes, larger sinuses, and larger occipital condyles than those of females. Male mandibles typically have squarer chins and thicker, rougher muscle attachments than female mandibles.

Craniometry

The cephalic index is the ratio of the width of the head, multiplied by 100 and divided by its length (front to back). The index is also used to categorize animals, especially dogs and cats. The width is usually measured just below the parietal eminence, and the length from the glabella to the occipital point.

Humans may be:

  • Dolichocephalic — long-headed
  • Mesaticephalic — medium-headed
  • Brachycephalic — short-headed[5]

Other animals

Fish

FishKeyDay
Fish head parts, 1889, Fauna of British India, Sir Francis Day

The skull of fishes is formed from a series of only loosely connected bones. Lampreys and sharks only possess a cartilaginous endocranium, with both the upper and lower jaws being separate elements. Bony fishes have additional dermal bone, forming a more or less coherent skull roof in lungfish and holost fish. The lower jaw defines a chin.

The simpler structure is found in jawless fish, in which the cranium is normally represented by a trough-like basket of cartilaginous elements only partially enclosing the brain, and associated with the capsules for the inner ears and the single nostril. Distinctively, these fish have no jaws.[22]

Cartilaginous fish, such as sharks and rays, have also simple, and presumably primitive, skull structures. The cranium is a single structure forming a case around the brain, enclosing the lower surface and the sides, but always at least partially open at the top as a large fontanelle. The most anterior part of the cranium includes a forward plate of cartilage, the rostrum, and capsules to enclose the olfactory organs. Behind these are the orbits, and then an additional pair of capsules enclosing the structure of the inner ear. Finally, the skull tapers towards the rear, where the foramen magnum lies immediately above a single condyle, articulating with the first vertebra. There are, in addition, at various points throughout the cranium, smaller foramina for the cranial nerves. The jaws consist of separate hoops of cartilage, almost always distinct from the cranium proper.[22]

Anarhichas lupus skull Iles de la Madeleine
Skull of an Atlantic wolffish

In ray-finned fishes, there has also been considerable modification from the primitive pattern. The roof of the skull is generally well formed, and although the exact relationship of its bones to those of tetrapods is unclear, they are usually given similar names for convenience. Other elements of the skull, however, may be reduced; there is little cheek region behind the enlarged orbits, and little, if any bone in between them. The upper jaw is often formed largely from the premaxilla, with the maxilla itself located further back, and an additional bone, the symplectic, linking the jaw to the rest of the cranium.[23]

Although the skulls of fossil lobe-finned fish resemble those of the early tetrapods, the same cannot be said of those of the living lungfishes. The skull roof is not fully formed, and consists of multiple, somewhat irregularly shaped bones with no direct relationship to those of tetrapods. The upper jaw is formed from the pterygoids and vomers alone, all of which bear teeth. Much of the skull is formed from cartilage, and its overall structure is reduced.[23]

Tetrapods

Tiktaalik skull front
Skull of Tiktaalik, an extinct genus transitional between lobe-finned fish and early tetrapods
Chelydra-serpentina3
Common snapping turtle

The skulls of the earliest tetrapods closely resembled those of their ancestors amongst the lobe-finned fishes. The skull roof is formed of a series of plate-like bones, including the maxilla, frontals, parietals, and lacrimals, among others. It is overlaying the endocranium, corresponding to the cartilaginous skull in sharks and rays. The various separate bones that compose the temporal bone of humans are also part of the skull roof series. A further plate composed of four pairs of bones forms the roof of the mouth; these include the vomer and palatine bones. The base of the cranium is formed from a ring of bones surrounding the foramen magnum and a median bone lying further forward; these are homologous with the occipital bone and parts of the sphenoid in mammals. Finally, the lower jaw is composed of multiple bones, only the most anterior of which (the dentary) is homologous with the mammalian mandible.[23]

In living tetrapods, a great many of the original bones have either disappeared or fused into one another in various arrangements.

Birds

CuckooSkull
Cuckoo skull
Anatidae-skull02
Side view of Anatidae skull

Birds have a diapsid skull, as in reptiles, with a prelacrymal fossa (present in some reptiles). The skull has a single occipital condyle.[24] The skull consists of five major bones: the frontal (top of head), parietal (back of head), premaxillary and nasal (top beak), and the mandible (bottom beak). The skull of a normal bird usually weighs about 1% of the bird's total bodyweight. The eye occupies a considerable amount of the skull and is surrounded by a sclerotic eye-ring, a ring of tiny bones. This characteristic is also seen in reptiles.

Amphibians

AmphibSkeletons
Amphibians skulls, Hans Gadow, 1909 Amphibia and Reptiles

Living amphibians typically have greatly reduced skulls, with many of the bones either absent or wholly or partly replaced by cartilage.[23] In mammals and birds, in particular, modifications of the skull occurred to allow for the expansion of the brain. The fusion between the various bones is especially notable in birds, in which the individual structures may be difficult to identify.

Structure

Fenestrae

Spinosaurus skull en
Scheme of Spinosaurus skull
Centrosaurus
A Centrosaurus skull
Massospondylus Skull Steveoc 86
The fenestrae in the skull of the dinosaur Massospondylus

The fenestrae (from Latin, meaning windows) are openings in the skull.

The temporal fenestrae are anatomical features of the skulls of several types of amniotes, 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 are critical for taxonomic classification of the synapsids, of which mammals are part.

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 two more advanced lines did: the synapsids (mammal-like reptiles) and the diapsids (most reptiles and later birds). As time progressed, diapsids' and synapsids' temporal fenestrae became more modified and larger to make stronger bites and more jaw muscles. Dinosaurs, which are diapsids, have large advanced openings, and their descendants, the birds, have temporal fenestrae which have been modified. Mammals, which are synapsids, possess one fenestral opening in the skull, situated to the rear of the orbit.

Classification

Chimpanzee skull
Chimpanzee skull
Goat skull-FMVZ USP-18.jpeg
Goat skull.

There are four types of amniote skull, classified by the number and location of their temporal fenestrae. These are:

  • 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

Evolutionarily, they are related as follows:

Bones

The jugal is a skull bone found in most reptiles, amphibians, and birds. In mammals, the jugal is often called the zygomatic bone or malar bone.

The prefrontal bone is a bone separating the lacrimal and frontal bones in many tetrapod skulls.

Terminology

Additional images

Mammals
Hippo skull dark

A hippopotamus skull

Skull of a Killer Whale (15712899202)

Killer whale skull

Ox skull

Ox

Birds
VautourCrane2

A vulture skull

Anatidae-skull03

Frontal view of Anatidae skull

Kiwi skull

Skull of a Kiwi

Storskarv - Kranium - Phalacrocorax carbo

Cranium of a Great cormorant.

The Childrens Museum of Indianapolis - Ostrich skull

Skull of a common ostrich

Woodpecker skull “Picidae sp.” at MAV-USP

Skull of a woodpecker

Reptiles
Ophiophagus hannah skull

King cobra skull

Ophthalmosaurus icenicus 1

An ichthyosaur skull

See also

References

This article incorporates text in the public domain from page 128 of the 20th edition of Gray's Anatomy (1918)

  1. ^ "skull". Merriam-Webster Dictionary. Archived from the original on 17 February 2015.
  2. ^ "Cephalization: Biology". Encyclopædia Britannica. Archived from the original on 2 May 2016. Retrieved 23 April 2016.
  3. ^ Carlson, Bruce M. (1999). Human Embryology & Developmental Biology (Second ed.). Mosby. pp. 166–170. ISBN 0-8151-1458-3.
  4. ^ Derkowski, Wojciech; Kędzia, Alicja; Glonek, Michał (2003). "Clinical anatomy of the human anterior cranial fossa during the prenatal period". Folia Morphologica. 62 (3): 271–3. PMID 14507064. Archived from the original on 24 September 2011.
  5. ^ a b Chaurasia, B. D. (2013). BD Chaurasia's Human Anatomy: Regional and Applied Dissection and Clinical. Volume 3: Head–Neck Brain (Sixth ed.). CBS Publishers & Distributors. pp. 29–30. ISBN 978-81-239-2332-1.
  6. ^ Silva, Sandra; Jeanty, Philippe (7 June 1999). "Cloverleaf skull or kleeblattschadel". TheFetus.net. MacroMedia. Archived from the original on 13 February 2008. Retrieved 3 February 2007.
  7. ^ a b c Slater, Bethany J.; Lenton, Kelly A.; Kwan, Matthew D.; Gupta, Deepak M.; Wan, Derrick C.; Longaker, Michael T. (April 2008). "Cranial Sutures: A Brief Review". Plastic and Reconstructive Surgery. 121 (4): 170e–8e. doi:10.1097/01.prs.0000304441.99483.97. PMID 18349596.
  8. ^ Gault, David T.; Renier, Dominique; Marchac, Daniel; Jones, Barry M. (September 1992). "Intracranial Pressure and Intracranial Volume in Children with Craniosynostosis". Plastic and Reconstructive Surgery. 90 (3): 377–81. doi:10.1097/00006534-199209000-00003. PMID 1513883.
  9. ^ Gaillard, Frank. "Copper beaten skull". Radiopaedia. Archived from the original on 25 April 2018. Retrieved 25 April 2018.
  10. ^ Holbourn, A. H. S. (9 October 1943). "Mechanics of Head Injuries". The Lancet. 242 (6267): 438–41. doi:10.1016/S0140-6736(00)87453-X.
  11. ^ "3D-Printed Polymer Skull Implant Used For First Time in US". Medical Daily. 7 March 2013. Archived from the original on 28 September 2013. Retrieved 24 September 2013.
  12. ^ "Dutch hospital gives patient new plastic skull, made by 3D printer". DutchNews.nl. 26 March 2014. Archived from the original on 28 March 2014.
  13. ^ Cohut, Maria (29 August 2018). "Newly discovered skull channels play role in immunity". Medical News Today. Retrieved 30 August 2018.
  14. ^ Ainsworth, Tiffiny A.; Spiegel, Jeffrey H. (2010). "Quality of life of individuals with and without facial feminization surgery or gender reassignment surgery". Quality of Life Research. 19 (7): 1019–24. doi:10.1007/s11136-010-9668-7. PMID 20461468.
  15. ^ Shams, Mohammad Ghasem; Motamedi, Mohammad Hosein Kalantar (9 January 2009). "Case report: Feminizing the male face". ePlasty. 9: e2. PMC 2627308. PMID 19198644.
  16. ^ World Professional Association for Transgender Health. WPATH Clarification on Medical Necessity of Treatment, Sex Reassignment, and Insurance Coverage in the U.S.A. Archived 30 September 2011 at the Wayback Machine (2008).
  17. ^ World Professional Association for Transgender Health. Standards of Care for the Health of Transsexual, Transgender, and Gender Nonconforming People, Version 7. Archived 3 March 2012 at the Wayback Machine pg. 58 (2011).
  18. ^ a b c Fee, Elizabeth (Fall 1979). "Nineteenth-Century Craniology: The Study of the Female Skull". Bulletin of the History of Medicine. 53 (3): 415–33.
  19. ^ "5d. The Interior of the Skull". Gray's Anatomy. Archived from the original on 31 March 2014. Retrieved 22 October 2014.
  20. ^ "Men May Be More Susceptible To Head Injury Than Women, Study Suggests". ScienceDaily. 22 January 2008. Archived from the original on 7 March 2012. Retrieved 6 June 2012.
  21. ^ Li, Haiyan; Ruan, Jesse; Xie, Zhonghua; Wang, Hao; Liu, Wengling (2007). "Investigation of the critical geometric characteristics of living human skulls utilising medical image analysis techniques". International Journal of Vehicle Safety. 2 (4): 345–367. doi:10.1504/IJVS.2007.016747.
  22. ^ a b Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 173–177. ISBN 0-03-910284-X.
  23. ^ a b c d Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 216–247. ISBN 0-03-910284-X.
  24. ^ Wing, Leonard W. (1956). "The Place of Birds in Nature". Natural History of Birds. The Ronald Press Company. pp. 22–23.

External links

Bohemia (rapper)

Roger David (born 15 October 1979), better known by his stage name Bohemia (Pakistani Punjabi: بوہیمیا, stylised BOHEMIA or Raja), is an Pakistani American rapper and record producer.

Calvary

Golgotha, or Calvary (Biblical Greek Γολγοθᾶ[ς] Golgotha[s], traditionally interpreted as reflecting Syriac (Aramaic) golgolta, as it were Hebrew gulgōleṯ (גולגולת), "skull"), was, according to the Gospels, a site immediately outside Jerusalem's walls where Jesus was crucified.Matthew's and Mark's gospels translate the term to mean "place of [the] skull" (Κρανίου Τόπος Kraníou Tópos), in Latin rendered Calvariæ Locus, from which the English word Calvary derives.

Its traditional site, identified by Helena of Constantinople, the mother of Constantine I, in 325, is at the site of the Church of the Holy Sepulchre. A 19th-century suggestion places it at the site now known as Skull Hill, some 500 m to the north (200 m north of Damascus Gate). Historian Joan Taylor bases a location c. 175 metres south-southeast of the traditional site on her reading of textual evidence.

Cosmic Cube

The Cosmic Cube is a fictional object appearing in American comic books published by Marvel Comics. It first appeared in the Marvel Universe in Tales of Suspense #79 (July 1966) and was created by Stan Lee and Jack Kirby.

Cranial nerves

Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), in contrast to spinal nerves (which emerge from segments of the spinal cord). 10 of the cranial nerves originate in the brainstem. Cranial nerves relay information between the brain and parts of the body, primarily to and from regions of the head and neck.Spinal nerves emerge sequentially from the spinal cord with the spinal nerve closest to the head (C1) emerging in the space above the first cervical vertebra. The cranial nerves, however, emerge from the central nervous system above this level. Each cranial nerve is paired and is present on both sides. Depending on definition in humans there are twelve or thirteen cranial nerves pairs, which are assigned Roman numerals I–XII, sometimes also including cranial nerve zero. The numbering of the cranial nerves is based on the order in which they emerge from the brain, front to back (brainstem).The terminal nerves (0), olfactory nerves (I) and optic nerves (II) emerge from the cerebrum or forebrain, and the remaining ten pairs arise from the brainstem, which is the lower part of the brain.The cranial nerves are considered components of the peripheral nervous system (PNS), although on a structural level the olfactory (I), optic (II), and trigeminal (V) nerves are more accurately considered part of the central nervous system (CNS).

Crossbones (comics)

Crossbones (Brock Rumlow) is a fictional supervillain appearing in American comic books published by Marvel Comics. The character is usually depicted as an adversary of Captain America, and played a part in his assassination.

The character has been adapted into multiple forms of media, most notably being portrayed by Frank Grillo in the Marvel Cinematic Universe.

Crystal skull

The crystal skulls are human skull hardstone carvings made of clear or milky white quartz (also called "rock crystal"), claimed to be pre-Columbian Mesoamerican artifacts by their alleged finders; however, these claims have been refuted for all of the specimens made available for scientific studies.

The results of these studies demonstrated that those examined were manufactured in the mid-19th century or later, almost certainly in Europe during a time when interest in ancient culture was abundant. The skulls were crafted in the 19th century in Germany, quite likely at workshops in the town of Idar-Oberstein, which was renowned for crafting objects made from imported Brazilian quartz in the late 19th century. Despite some claims presented in an assortment of popularizing literature, legends of crystal skulls with mystical powers do not figure in genuine Mesoamerican or other Native American mythologies and spiritual accounts.The skulls are often claimed to exhibit paranormal phenomena by some members of the New Age movement, and have often been portrayed as such in fiction. Crystal skulls have been a popular subject appearing in numerous sci-fi television series, novels, films, and video games.

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 crocodiles, lizards, snakes, tuatara, turtles, and birds. Although some diapsids have lost either one hole (lizards), or both holes (snakes and turtles), or have a heavily restructured skull (modern birds), they are still classified as diapsids based on their ancestry. At least 7,925 species of diapsid reptiles exist in environments around the world today (nearly 18,000 when birds are included).

Fibrous joint

Fibrous joints are connected by dense connective tissue, consisting mainly of collagen. These are fixed joints where bones are united by a layer of white fibrous tissue of varying thickness. In the skull the joints between the bones are called sutures. Such immovable joints are also referred to as synarthroses.

Human skeleton

The human skeleton is the internal framework of the body. It is composed of around 270 bones at birth – this total decreases to around 206 bones by adulthood after some bones get fused together. The bone mass in the skeleton reaches maximum density around age 21. The human skeleton can be divided into the axial skeleton and the appendicular skeleton. The axial skeleton is formed by the vertebral column, the rib cage, the skull and other associated bones. The appendicular skeleton, which is attached to the axial skeleton, is formed by the shoulder girdle, the pelvic girdle and the bones of the upper and lower limbs.

The human skeleton performs six major functions; support, movement, protection, production of blood cells, storage of minerals, and endocrine regulation.

The human skeleton is not as sexually dimorphic as that of many other primate species, but subtle differences between sexes in the morphology of the skull, dentition, long bones, and pelvis exist. In general, female skeletal elements tend to be smaller and less robust than corresponding male elements within a given population. The human female pelvis is also different from that of males in order to facilitate childbirth. Unlike most primates, human males do not have penile bones.

Indiana Jones and the Kingdom of the Crystal Skull

Indiana Jones and the Kingdom of the Crystal Skull is a 2008 American action-adventure film directed by Steven Spielberg and the fourth installment in the Indiana Jones series. Released nineteen years after the previous film, the film is set in 1957, pitting Indiana Jones (Harrison Ford) against Soviet agents—led by Irina Spalko (Cate Blanchett)—searching for a telepathic crystal skull. Jones is aided by his former lover, Marion Ravenwood (Karen Allen), and her son, Mutt Williams (Shia LaBeouf). Ray Winstone, John Hurt, and Jim Broadbent are also part of the supporting cast.

Screenwriters Jeb Stuart, Jeffrey Boam, Frank Darabont, and Jeff Nathanson wrote drafts before David Koepp's script satisfied the producers. The filmmakers intended to pay tribute to the science fiction B-movies of the 1950s era. Shooting began on June 18, 2007, at various locations in New Mexico, New Haven, Connecticut, Hawaii, and Fresno, California, as well as on sound stages in Los Angeles. To maintain aesthetic continuity with the previous films, the crew relied on traditional stunt work instead of computer-generated stunt doubles, and cinematographer Janusz Kamiński studied Douglas Slocombe's style from the previous films.

The film premiered at the 2008 Cannes Film Festival on May 18, 2008, and was released worldwide on May 22, 2008 to generally positive reviews with praise for the performances, action scenes, John Williams' musical score, and the costume design. Criticism, however, focused on the dialogue, storyline, pacing, and overuse of CGI. It was also a financial success like the previous three films in the series, grossing over $786 million worldwide, becoming the franchise's highest-grossing film when not adjusted for inflation, as well as the second-highest-grossing film of 2008. The film is scheduled to be followed by an untitled fifth film, planned for release on July 9, 2021, with both Spielberg and Ford returning.

Martin McDonagh

Martin Faranan McDonagh (; born 26 March 1970) is an Irish playwright, screenwriter, producer, and director. Born and brought up in London, the son of Irish parents. He is among the most acclaimed living ‘Irish’ playwrights. A winner of the Academy Award for Best Live Action Short Film, McDonagh has been nominated for three other Academy Awards, and in 2018 won three BAFTA Awards from four nominations and two Golden Globe Awards from three nominations for his film Three Billboards Outside Ebbing, Missouri.

MonsterVerse

The MonsterVerse is an American media franchise and shared fictional universe that is centered on a series of monster films featuring Godzilla and King Kong, produced by Legendary Entertainment and co-produced and distributed by Warner Bros. The first installment was Godzilla (2014), a reboot of the Godzilla franchise, which was followed by Kong: Skull Island (2017), a reboot of the King Kong franchise. The next film to be released will be Godzilla: King of the Monsters (2019), followed by Godzilla vs. Kong (2020). With two films released to date, the series has grossed over $1 billion worldwide.

Red Skull

The Red Skull (Johann Schmidt) is a fictional supervillain appearing in American comic books published by Marvel Comics. The character is usually depicted as the archenemy of the superhero Captain America. Portrayed as a Nazi agent, the character was created by Joe Simon and Jack Kirby, and first appeared in Captain America Comics #7 (October 1941).

The character has been adapted to a variety of other media platforms, including animated television series, video games and live-action feature films. He was portrayed by actor Scott Paulin in the 1990 direct-to-video film Captain America, and then by Hugo Weaving in the 2011 film Captain America: The First Avenger and by Ross Marquand in the 2018 film Avengers: Infinity War, the latter two both set in the Marvel Cinematic Universe.

The Red Skull was ranked number 21 on Wizard magazine's Top 100 Greatest Villains Ever list and ranked as IGN's 14th Greatest Comic Book Villain of All Time.

Sagittal crest

A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are exceptionally strong jaw muscles. The sagittal crest serves primarily for attachment of the temporalis muscle, which is one of the main chewing muscles. Development of the sagittal crest is thought to be connected to the development of this muscle. A sagittal crest usually develops during the juvenile stage of an animal in conjunction with the growth of the temporalis muscle, as a result of convergence and gradual heightening of the temporal lines.

Shannara

Shannara is a series of high fantasy novels written by Terry Brooks, beginning with The Sword of Shannara in 1977 and continuing through The Skaar Invasion which was released in June 2018; there is also a prequel, First King of Shannara. The series blends magic and primitive technology and is set in the Four Lands, which are identified as Earth long after civilization was destroyed in a chemical and nuclear holocaust called the Great Wars. By the time of the prequel First King of Shannara, the world had reverted to a pre-industrial state and magic had re-emerged to supplement science.

Skull and Bones

Skull and Bones is an undergraduate senior secret student society at Yale University in New Haven, Connecticut. The oldest senior class society at the university, Skull and Bones has become a cultural institution known for its powerful alumni and various conspiracy theories. The society's alumni organization, the Russell Trust Association, owns the organization's real estate and oversees the membership. The society is known informally as "Bones", and members are known as "Bonesmen".

Trepanning

Trepanning, also known as trepanation, trephination, trephining or making a burr hole (the verb trepan derives from Old French from Medieval Latin trepanum from Greek trypanon, literally "borer, auger") is a surgical intervention in which a hole is drilled or scraped into the human skull, exposing the dura mater to treat health problems related to intracranial diseases or release pressured blood buildup from an injury. It may also refer to any "burr" hole created through other body surfaces, including nail beds. It is often used to relieve pressure beneath a surface. A trephine is an instrument used for cutting out a round piece of skull bone.

In ancient times, holes were drilled into a person who was behaving in what was considered an abnormal way to let out what people believed were evil spirits. Evidence of trepanation has been found in prehistoric human remains from Neolithic times onward. The bone that was trepanned was kept by the prehistoric people and may have been worn as a charm to keep evil spirits away. Evidence also suggests that trepanation was primitive emergency surgery after head wounds to remove shattered bits of bone from a fractured skull and clean out the blood that often pools under the skull after a blow to the head. Such injuries were typical for primitive weaponry such as slings and war clubs. There is some contemporary use of the term. In modern eye surgery, a trephine instrument is used in corneal transplant surgery. The procedure of drilling a hole through a fingernail or toenail is also known as trephination. It is performed by a physician or surgeon to relieve the pain associated with a subungual hematoma (blood under the nail); a small amount of blood is expressed through the hole and the pain associated with the pressure is partially alleviated. In abdominal surgery, a trephine incision is when a small disc of abdominal skin is excised to accommodate a stoma. Although the abdominal wall does not contain bone, the use of the word 'trephine' in this context may relate to the round excised area of skin being similar in shape to a burr hole.

WWE Championship

The WWE Championship is a world heavyweight championship created and promoted by the American professional wrestling promotion WWE on the SmackDown brand. It is one of two world titles for WWE's main roster, alongside the WWE Universal Championship that was created for the Raw brand as a result of the 2016 WWE draft. The current champion is Kofi Kingston, who is in his first reign.

The original world championship of the promotion, it was established by the then-World Wide Wrestling Federation (WWWF) on April 25, 1963 as the WWWF World Heavyweight Championship, following the promotion seceding from the National Wrestling Alliance (NWA). The inaugural champion was Buddy Rogers. Since its inception, the title has undergone many name changes due to company name changes and title unifications. It is the oldest championship currently active in the WWE, and is presented as being the promotion's most prestigious title, with many matches for the title having headlined pay-per-view events – including WWE's flagship event WrestleMania. In professional wrestling in general, it is considered by many to be one of the most prestigious championships of all time.From its inception until 2001, it was promoted as WWE's sole primary championship. An additional world title, the WCW Championship, was added after the then-World Wrestling Federation's purchase of World Championship Wrestling in early 2001. The titles were later unified as the Undisputed Championship. After the first brand extension in 2002 and the promotion becoming the WWE, the championship became exclusive to SmackDown, and the World Heavyweight Championship was created for Raw. ECW became a third brand in 2006, adding the ECW World Heavyweight Championship. Over the course of the first brand extension, the WWE Championship switched between brands, usually as a result of the annual draft. The ECW Championship was deactivated in 2010, and the World Heavyweight Championship was unified with the WWE Championship in 2013. The championship was again the sole world title of WWE's main roster until the reintroduction of the brand extension in 2016.

Syndesmosis
Sutures
Mouth
The neurocranium of the skull
Occipital
Parietal
Frontal
Temporal
Sphenoid
Ethmoid
Maxilla
Zygomatic
Palatine
Mandible
Nose
Other
Compound structures of skull
Neurocranium
Facial skeleton
Both
Musculoskeletal
Circulatory system
Nervous system
Integumentary system
Immune system
Respiratory system
Digestive system
Urinary system
Reproductive system
Endocrine system

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.