Editing Human skeleton

{{short description|Internal framework of the human body}}
{{redirect|Bone structure|skeletal systems of other animals|Skeleton|the scientific study of bones|Osteology}}
{{pp|small=yes}}
{{Infobox anatomy
|Name = Human skeleton
|Greek = σκελετός
|Image = File:Human-Skeleton.jpg
|Caption = A human skeleton on exhibit at the [[Museum of Osteology]], [[Oklahoma City, Oklahoma]]
|Width = 100px
}}

The '''human skeleton''' is the internal framework of the [[human body]]. It is composed of around 270 [[bone]]s at birth – this total decreases to around 206 bones by adulthood after some bones get fused together.<ref>{{cite book|title=Mammal anatomy : an illustrated guide.|date=2010|publisher=Marshall Cavendish|location=New York|isbn=9780761478829|page=129|url=https://books.google.com/books?id=mTPI_d9fyLAC&pg=PA129}}</ref> The bone mass in the skeleton makes up about 14% of the total body weight (ca. 10–11&nbsp;kg for an average person) and reaches maximum mass between the ages of 25 and 30.<ref>{{cite web |title=Healthy Bones at Every Age |url=https://orthoinfo.aaos.org/en/staying-healthy/healthy-bones-at-every-age/ |website=OrthoInfo |publisher=American Academy of Orthopaedic Surgeons |access-date=6 January 2023 |archive-url=https://web.archive.org/web/20221118205631/https://orthoinfo.aaos.org/en/staying-healthy/healthy-bones-at-every-age/ |archive-date=18 November 2022 |url-status=live }}</ref> The human skeleton can be divided into the [[axial skeleton]] and the [[appendicular skeleton]]. The axial skeleton is formed by the [[human vertebral column|vertebral column]], the [[human rib cage|rib cage]], the [[human skull|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 (biology)|morphology]] of the skull, [[dentition]], [[long bone]]s, 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]].<ref>''Thieme Atlas of Anatomy'', (2006), p 113</ref> Unlike most primates, human males do not have [[penile bone]]s.<ref name="patterns">''Patterns of Sexual Behavior''  Clellan S. Ford and Frank A. Beach, published by Harper & Row, New York in 1951. {{ISBN|0-313-22355-6}}</ref>

==Divisions==
{{No citations section|date=September 2024}}

===Axial===
{{Main|Axial skeleton}}
The axial skeleton (80 bones) is formed by the [[human vertebral column|vertebral column]] (32–34 bones; the number of the vertebrae differs from human to human as the lower 2 parts, sacral and coccygeal bone may vary in length), a part of the [[human rib cage|rib cage]] (12 pairs of [[rib]]s and the [[Human sternum|sternum]]), and the [[human skull|skull]] (22 bones and 7 associated bones).

The upright posture of humans is maintained by the axial skeleton, which transmits the weight from the head, the trunk, and the upper extremities down to the lower extremities at the [[hip joint]]s. The bones of the spine are supported by many ligaments. The [[erector spinae muscles]] are also supporting and are useful for balance.

===Appendicular===
{{Main|Appendicular skeleton}}
The appendicular skeleton (126 bones) is formed by the pectoral girdles, the upper limbs, the pelvic girdle or pelvis, and the lower limbs. Their functions are to make locomotion possible and to protect the major organs of digestion, excretion and reproduction.

==Functions==

The skeleton serves six major functions: support, movement, protection, production of blood cells, storage of minerals and endocrine regulation.{{Citation needed|date=September 2024}}

===Support===
The skeleton provides the framework which supports the body and maintains its shape. The pelvis, associated ligaments and muscles provide a floor for the pelvic structures. Without the rib cages, [[costal cartilage]]s, and [[intercostal muscle]]s, the [[human lungs|lungs]] would collapse.{{Citation needed|date=September 2024}}

===Movement===
The joints between bones allow movement, some allowing a wider range of movement than others, e.g. the ball and socket joint allows a greater range of movement than the pivot joint at the neck. Movement is powered by [[skeletal muscle]]s, which are attached to the skeleton at various sites on bones. Muscles, bones, and joints provide the principal mechanics for movement, all coordinated by the nervous system.

It is believed that the reduction of human bone density in prehistoric times reduced the agility and dexterity of human movement. Shifting from hunting to [[agriculture]] has caused human bone density to reduce significantly.<ref>{{cite magazine |title=Switching Farming Made Human Bone Skeleton Joint Lighter |url=http://www.smithsonianmag.com/science-nature/switching-farming-made-human-joint-bones-lighter-180953711/?no-ist |url-access=subscription |archive-url=https://web.archive.org/web/20150321112852/https://www.smithsonianmag.com/science-nature/switching-farming-made-human-joint-bones-lighter-180953711/ |archive-date=21 March 2015 |last=Thompson |first=Helen |magazine=[[Smithsonian (magazine)|Smithsonian]] |date=23 December 2014 |access-date=16 July 2024}}{{cbignore}}</ref><ref>{{cite web |url=http://www.world-science.net/othernews/141223_skeleton.htm |url-status=dead |archive-url=https://web.archive.org/web/20150316080428/http://www.world-science.net/othernews/141223_skeleton.htm |archive-date=16 March 2015 |title=Light human skeleton may have come after agriculture |access-date=16 July 2024 |website=World Science}}{{cbignore}}</ref><ref>{{cite web|url=http://blogs.discovermagazine.com/d-brief/2014/12/22/with-the-advent-of-agriculture-human-bones-dramatically-weakened/|title=With the Advent of Agriculture, Human Bones Dramatically Weakened|date=22 December 2014|access-date=4 March 2017|archive-date=13 March 2017|archive-url=https://web.archive.org/web/20170313214116/http://blogs.discovermagazine.com/d-brief/2014/12/22/with-the-advent-of-agriculture-human-bones-dramatically-weakened/|url-status=dead}}</ref>

===Protection===
The skeleton helps to protect many vital internal [[organ (anatomy)|organs]] from being damaged.{{Citation needed|date=September 2024}}
* The skull protects the [[human brain|brain]]
* The [[vertebrae]] protect the [[spinal cord]].
* The [[rib cage]], [[vertebral column|spine]], and [[sternum]] protect the [[lungs]], [[heart]] and major [[blood vessel]]s.

===Blood cell production===
The skeleton is the site of [[haematopoiesis]], the development of [[blood cells]] that takes place in the [[bone marrow]]. In children, haematopoiesis occurs primarily in the marrow of the long bones such as the femur and tibia. In adults, it occurs mainly in the pelvis, cranium, vertebrae, and sternum.<ref>{{cite journal|last=Fernández|first=KS|author2=de Alarcón, PA|title=Development of the hematopoietic system and disorders of hematopoiesis that present during infancy and early childhood.|journal=Pediatric Clinics of North America|date=Dec 2013|volume=60|issue=6|pages=1273–89|pmid=24237971|doi=10.1016/j.pcl.2013.08.002}}</ref>

===Storage===
The [[Osteon|bone matrix]] can store [[calcium]] and is involved in [[calcium metabolism]], and [[bone marrow]] can store [[iron]] in [[ferritin]] and is involved in [[Human iron metabolism|iron metabolism]]. However, bones are not entirely made of calcium, but a mixture of [[chondroitin sulfate]] and [[hydroxyapatite]], the latter making up 70% of a bone. Hydroxyapatite is in turn composed of 39.8% of calcium, 41.4% of oxygen, 18.5% of phosphorus, and 0.2% of hydrogen by mass. Chondroitin sulfate is a sugar made up primarily of oxygen and carbon.{{Citation needed|date=September 2024}}

===Endocrine regulation===
Bone cells release a [[hormone]] called [[osteocalcin]], which contributes to the regulation of [[blood sugar]] ([[glucose]]) and [[body fat|fat deposition]]. Osteocalcin increases both [[insulin]] secretion and sensitivity, in addition to boosting the number of [[insulin-producing cell]]s and reducing stores of fat.<ref>{{cite journal |doi=10.1016/j.cell.2007.05.047 |title=Endocrine Regulation of Energy Metabolism by the Skeleton |year=2007 |last1=Lee |first1=Na Kyung |last2=Sowa |first2=Hideaki |last3=Hinoi |first3=Eiichi |last4=Ferron |first4=Mathieu |last5=Ahn |first5=Jong Deok |last6=Confavreux |first6=Cyrille |last7=Dacquin |first7=Romain |last8=Mee |first8=Patrick J. |last9=McKee |first9=Marc D. |last10=Jung |first10=Dae Young |last11=Zhang |first11=Zhiyou |last12=Kim |first12=Jason K. |last13=Mauvais-Jarvis |first13=Franck |last14=Ducy |first14=Patricia |last15=Karsenty |first15=Gerard |journal=Cell |volume=130 |issue=3 |pages=456–69 |pmid=17693256 |pmc=2013746}}</ref>

==Sex differences==
[[File:Yorkshire Museum - skeleton of a wealthy woman 1.jpg|thumb|During construction of the York to [[Scarborough Railway Bridge]] in 1901, workmen discovered a large stone coffin, close to the [[River Ouse, Yorkshire|River Ouse]]. Inside was a skeleton, accompanied by an array of unusual and expensive objects. This chance find represents one of the most significant discoveries ever made from [[Eboracum#Late Roman York|Roman York]]. Study of the skeleton has revealed that it belonged to a woman.]]

Anatomical differences between human males and females are highly pronounced in some soft tissue areas, but tend to be limited in the skeleton. The human skeleton is not as [[sexually dimorphic]] as that of many other primate species, but subtle differences between sexes in the [[Morphology (biology)|morphology]] of the skull, [[dentition]], [[long bone]]s, and pelvis are exhibited across human populations. In general, female skeletal elements tend to be smaller and less robust than corresponding male elements within a given population.{{cn|date=July 2021}} It is not known whether or to what extent those differences are genetic or environmental.

===Skull===
A variety of gross morphological traits of the human skull demonstrate sexual dimorphism, such as the median [[nuchal line]], [[mastoid process]]es, [[supraorbital margin]], [[supraorbital ridge]], and the [[chin]].<ref>{{cite book|last=Buikstra|first=J.E.|title=Standards for data collection from human skeletal remains|year=1994|publisher=Arkansas Archaeological Survey|pages=208|author2=D.H. Ubelaker}}</ref>

===Dentition===
Human inter-sex dental dimorphism centers on the [[canine teeth]], but it is not nearly as pronounced as in the other [[great apes]].

===Long bones===
Long bones are generally larger in males than in females within a given population. Muscle attachment sites on long bones are often more robust in males than in females, reflecting a difference in overall muscle mass and development between sexes. Sexual dimorphism in the long bones is commonly characterized by [[morphometric]] or gross morphological analyses.{{Citation needed|date=September 2024}}

===Pelvis===
The human pelvis exhibits greater sexual dimorphism than other bones, specifically in the size and shape of the [[pelvic cavity]], [[Ilium (bone)|ilia]], greater sciatic notches, and the sub-pubic angle. The [[Phenice method]] is commonly used to determine the sex of an unidentified human skeleton by anthropologists with 96% to 100% accuracy in some populations.<ref>{{cite journal |doi=10.1002/ajpa.1330300214 |title=A newly developed visual method of sexing the os pubis |year=1969 |last1=Phenice |first1=T. W. |journal=American Journal of Physical Anthropology |volume=30 |issue=2 |pages=297–301 |pmid=5772048}}</ref>

Women's pelvises are wider in the pelvic inlet and are wider throughout the pelvis to allow for child birth. The [[sacrum]] in the women's pelvis is curved inwards to allow the child to have a "[[funnel]]" to assist in the child's pathway from the uterus to the [[birth canal]].

==Clinical significance==
{{See also|Bone disease}}
There are many classified skeletal disorders. One of the most common is [[osteoporosis]]. Also common is [[scoliosis]], a side-to-side curve in the back or spine, often creating a pronounced "C" or "S" shape when viewed on an x-ray of the spine. This condition is most apparent during adolescence, and is most common with females.{{Citation needed|date=September 2024}}

===Arthritis===
{{Main|Arthritis}}

Arthritis is a [[disease|disorder]] of the joints. It involves inflammation of one or more joints. When affected by arthritis, the joint or joints affected may be painful to move, may move in unusual directions or may be immobile completely. The symptoms of arthritis will vary differently between types of arthritis. The most common form of arthritis, [[osteoarthritis]], can affect both the larger and smaller joints of the human skeleton. The [[cartilage]] in the affected joints will degrade, soften and wear away. This decreases the mobility of the joints and decreases the space between bones where cartilage should be.{{Citation needed|date=September 2024}}

===Osteoporosis===
{{Main|Osteoporosis}}
Osteoporosis is a disease of bone where there is reduced [[bone mineral density]], increasing the likelihood of [[bone fracture|fractures]].<ref name=DAVIDSONS2010>{{cite book|last=Britton|first=the editors Nicki R. Colledge, Brian R. Walker, Stuart H. Ralston; illustrated by Robert|title=Davidson's principles and practice of medicine.|date=2010|publisher=Churchill Livingstone/Elsevier|location=Edinburgh|isbn=978-0-7020-3085-7|pages=1116–1121|edition=21st}}</ref>  Osteoporosis is defined by the [[World Health Organization]] in women as a bone mineral density 2.5 [[standard deviation]]s below peak bone mass, relative to the age and sex-matched average, as measured by [[dual energy X-ray absorptiometry]], with the term "established osteoporosis" including the presence of a [[fragility fracture]].<ref name=WHO1994>{{cite journal |author=WHO |title=Assessment of fracture risk and its application to screening for postmenopausal osteoporosis. Report of a WHO Study Group |journal=World Health Organization Technical Report Series |volume=843 |pages=1–129 |year=1994 |pmid=7941614 }}</ref> Osteoporosis is most common in women after [[menopause]], when it is called "postmenopausal osteoporosis", but may develop in men and premenopausal women in the presence of particular hormonal disorders and other [[Chronic (medicine)|chronic]] diseases or as a result of [[tobacco smoking|smoking]] and [[medication]]s, specifically [[glucocorticoid]]s.<ref name=DAVIDSONS2010 /> Osteoporosis usually has no symptoms until a fracture occurs.<ref name=DAVIDSONS2010 /> For this reason, DEXA scans are often done in people with one or more risk factors, who have developed osteoporosis and be at risk of fracture.<ref name=DAVIDSONS2010 />

Osteoporosis treatment includes advice to stop smoking, decrease alcohol consumption, exercise regularly, and have a healthy diet. [[Calcium]] supplements may also be advised, as may [[vitamin D]]. When medication is used, it may include [[bisphosphonate]]s, [[strontium ranelate]], and osteoporosis may be one factor considered when commencing [[hormone replacement therapy]].<ref name=DAVIDSONS2010 />

==History==
{{See also|Paleoanthropology}}
===India===
{{main|Ayurveda}}
The ''[[Sushruta Samhita]]'', composed between the 6th century&nbsp;[[BCE]] and 5th century&nbsp;CE speaks of 360 bones. Books on ''Salya-Shastra'' (surgical science) know of only 300. The text then lists the total of 300 as follows: 120 in the extremities (e.g. hands, legs), 117 in the pelvic area, sides, back, abdomen and breast, and 63 in the neck and upwards.{{Sfn|Hoernle|1907|p=70}} The text then explains how these subtotals were empirically verified.{{Sfn|Hoernle|1907|pp=70-72}} The discussion shows that the Indian tradition nurtured diversity of thought, with Sushruta school reaching its own conclusions and differing from the Atreya-Caraka tradition.{{Sfn|Hoernle|1907|pp=70-72}} The differences in the count of bones in the two schools is partly because Charaka Samhita includes 32 [[tooth sockets]] in its count, and their difference of opinions on how and when to count a cartilage as bone (which both sometimes do, unlike modern anatomy).{{Sfn|Hoernle|1907|pp=73-74}}

===Hellenistic world===
The study of bones in ancient Greece started under [[Ptolemaic kings]] due to their link to Egypt. [[Herophilos]], through his work by studying dissected human corpses in Alexandria, is credited to be the pioneer of the field. His works are lost but are often cited by notable persons in the field such as [[Galen]] and [[Rufus of Ephesus]]. Galen himself did little dissection though and relied on the work of others like Marinus of Alexandria,<ref>{{cite journal|last1=Rocca|first1=Julius|title=A Note on Marinus of Alexandria|journal=Journal of the History of the Neurosciences|date=9 August 2010|volume=11|issue=3|pages=282–285|doi=10.1076/jhin.11.3.282.10386|pmid=12481479|s2cid=37476347}}</ref> as well as his own observations of gladiator cadavers and animals.<ref>{{cite journal|last1=Charlier|first1=Philippe|last2=Huynh-Charlier|first2=Isabelle|last3=Poupon|first3=Joël|last4=Lancelot|first4=Eloïse|last5=Campos|first5=Paula F.|last6=Favier|first6=Dominique|last7=Jeannel|first7=Gaël-François|last8=Bonati|first8=Maurizio Rippa|last9=Grandmaison|first9=Geoffroy Lorin de la|last10=Herve|first10=Christian|title=Special report: Anatomical pathology A glimpse into the early origins of medieval anatomy through the oldest conserved human dissection (Western Europe, 13th c. A.D.)|journal=Archives of Medical Science|date=2014|volume=2|issue=2|pages=366–373|doi=10.5114/aoms.2013.33331|pmc=4042035|pmid=24904674}}</ref> According to [[Katherine Park]], in medieval Europe dissection continued to be practiced, contrary to the popular understanding that such practices were taboo and thus completely banned.<ref>{{cite web|title=Debunking a myth|url=http://news.harvard.edu/gazette/story/2011/04/debunking-a-myth/|website=Harvard Gazette|date=7 April 2011 |access-date=12 November 2016}}</ref> The practice of ''holy autopsy'', such as in the case of [[Clare of Montefalco]] further supports the claim.<ref>{{cite book|last1=Hairston|first1=Julia L.|last2=Stephens|first2=Walter|title=The body in early modern Italy|date=2010|publisher=Johns Hopkins University Press|location=Baltimore|isbn=9780801894145}}</ref> Alexandria continued as a center of anatomy under Islamic rule, with [[Ibn Zuhr]] a notable figure. Chinese understandings are divergent, as the closest corresponding concept in the medicinal system seems to be the [[Meridian (Chinese medicine)|meridians]], although given that [[Hua Tuo]] regularly performed surgery, there may be some distance between medical theory and actual understanding.

===Renaissance===
[[Leonardo da Vinci]] made studies of the skeleton, albeit unpublished in his time.<ref>{{cite web|last1=Sooke|first1=Alastair|title=Leonardo da Vinci: Anatomy of an artist|url=https://www.telegraph.co.uk/culture/art/leonardo-da-vinci/10202124/Leonardo-da-Vinci-Anatomy-of-an-artist.html|website=Telegraph.co.uk|access-date=9 December 2016}}</ref> Many artists, [[Antonio del Pollaiuolo]] being the first, performed dissections for better understanding of the body, although they concentrated mostly on the muscles.<ref>{{cite web |last1=Bambach |first1=Carmen |author-link1=Carmen C. Bambach |title=Anatomy in the Renaissance |url=http://www.metmuseum.org/TOAH/HD/anat/hd_anat.htm |website=The Met’s Heilbrunn Timeline of Art History}}</ref> [[Vesalius]], regarded as the founder of modern anatomy, authored the book ''[[De humani corporis fabrica]]'', which contained many illustrations of the skeleton and other body parts, correcting some theories dating from Galen, such as the lower jaw being a single bone instead of two.<ref>{{cite web|title=Vesalius's Renaissance anatomy lessons|url=http://www.bl.uk/learning/cult/bodies/vesalius/renaissance.html|website=www.bl.uk|access-date=18 December 2016|archive-date=20 December 2016|archive-url=https://web.archive.org/web/20161220180207/http://www.bl.uk/learning/cult/bodies/vesalius/renaissance.html}}</ref> Various other figures like [[Alessandro Achillini]] also contributed to the further understanding of the skeleton.

===18th century===
As early as 1797, the death [[goddess]] or [[folk saint]] known as [[Santa Muerte]] has been represented as a skeleton.<ref>{{cite book|last=Chesnut |first=R. Andrew |year=2018|orig-year=2012|title=Devoted to Death: Santa Muerte, the Skeleton Saint|url=https://books.google.com/books?id=ul0vDwAAQBAJ |edition=Second|location=New York|publisher=[[Oxford University Press]]|doi=10.1093/acprof:oso/9780199764662.001.0001|isbn=978-0-19-063332-5|lccn=2011009177|access-date=2021-11-30}}</ref><ref>{{cite web|author=Livia Gershon|title=Who is Santa Muerte?|url=https://daily.jstor.org/who-is-santa-muerte/|publisher=[[JSTOR#Content|JSTOR Daily]]|date=October 5, 2020|access-date=2021-11-30}}</ref>

==See also==
*[[List of bones of the human skeleton]]
*[[Distraction osteogenesis]]

==References==
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{{Commons category|Human skeletons}}
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===Bibliography===
*{{Cite book|title = Studies in the Medicine of Ancient India: Osteology or the Bones of the Human Body|last = Hoernle|first = A. F. Rudolf|publisher = Clarendon Press|year = 1907|author-link = Rudolf Hoernle|location = Oxford, UK | url = https://archive.org/stream/studiesinmedicin01hoeruoft#page/n3/mode/2up}}

==Further reading==
* {{cite book |title=Skeleton Keys: The Secret Life of Bone |year=2019 |author=Riley Black (formerly Brian Switek) |publisher=Riverhead Books |isbn=978-0399184901}}

{{Bones of skeleton}}

{{Human systems and organs}}
{{Authority control}}

{{DEFAULTSORT:Human Skeleton}}
[[Category:Endocrine system]]
[[Category:Human anatomy]]
[[Category:Skeletal system| ]]