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[[Image:Human_skeleton_front.svg|thumb|350px|A diagram of the human skeleton]]
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The '''human skeleton''' is the internal framework of the body. It is composed of 270 [[bone]]s at birth<ref>{{cite web
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[[Image:Human_skeleton_front.svg|thumb|350px]]
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The '''human skeleton''' is composed of 270 bones at birth<ref>{{cite web
|url = http://www.groundreport.com/Health_and_Science/We-re-Born-With-270-Bones-As-Adults-We-Have-206
|url = http://www.groundreport.com/Health_and_Science/We-re-Born-With-270-Bones-As-Adults-We-Have-206
|title = We're Born With 300 Bones. As Adults We Have 206
|title = We're Born With 300 Bones. As Adults We Have 206
|first = Larry | last = Miller
|first = Larry | last = Miller
|date = 2007-12-09 | publisher = Ground Report
|date = 2007-12-09 | publisher = Ground Report
}}</ref><ref>{{cite web|url=http://ask.yahoo.com/20010808.html |title=How many bones does the human body contain? |publisher=Ask.yahoo.com |date=2001-08-08 |accessdate=2010-03-04}}</ref><ref>[http://education.sdsc.edu/download/enrich/exploring_human.pdf Exploring our human bodies]. San Diego Supercomputer Center Education</ref> and by the time adulthood is reached, some bones have fused together to give a total of 206 bones in the body. The bone mass in the skeleton reaches maximum density around age 30. 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]] and the [[human skull|skull]]. The appendicular skeleton, which is attached to the axial skeleton, is formed by the [[pectoral girdle]]s, the [[pelvic girdle]] and the bones of the upper and lower limbs.
}}</ref><ref>{{cite web|url=http://ask.yahoo.com/20010808.html |title=How many bones does the human body contain? |publisher=Ask.yahoo.com |date=2001-08-08 |accessdate=2010-03-04}}</ref><ref>[http://education.sdsc.edu/download/enrich/exploring_human.pdf Exploring our human bodies]. San Diego Supercomputer Center Education</ref> - this total decreases to 206 bones by adulthood after some bones have fused together. The bone mass in the skeleton reaches maximum density around age 30. 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]] and the [[human skull|skull]]. The appendicular skeleton, which is attached to the axial skeleton, is formed by the [[pectoral girdle]]s, the [[pelvic girdle]] and the bones of the upper and lower limbs.


The human skeleton serves six major functions; support, movement, protection, production of [[blood cells]], storage of ions and endocrine regulation.
The human skeleton serves six major functions; support, movement, protection, production of [[blood cells]], storage of ions and endocrine regulation.


The human skeleton is not as [[Sexual dimorphism|sexually dimorphic]] as that of many other primate species, but subtle differences between sexes in the [[Morphology (biology)|morphology]] of the [[Human skull|skull]], [[dentition]], [[long bone]]s, and pelves exist. In general, female skeletal elements tend to be smaller and less robust than corresponding male elements within a given population. The pelvis in female skeletons is also different from that of males in order to facilitate child birth.
The human skeleton is not as [[Sexual dimorphism|sexually dimorphic]] as that of many other primate species, but subtle differences between sexes in the [[Morphology (biology)|morphology]] of the [[Human skull|skull]], [[dentition]], [[long bone]]s, and pelves exist. In general, female skeletal elements tend to be smaller and less robust than corresponding male elements within a given population. The pelvis in female skeletons is also different from that of males in order to facilitate child birth.

==Divisions==
==Divisions==

===Axial skeleton===
===Axial skeleton===
{{Main|Axial skeleton}}
{{Main|Axial skeleton}}
The axial skeleton (80 bones) is formed by the [[human vertebral column|vertebral column]] (32-34; the number of the vertebrae differs from human to human as the lower 2 parts, sacral and coccygeal bone may vary in length), 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|erectors spinae]] muscles are also supporting and are useful for balance.
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), 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|erectors spinae]] muscles are also supporting and are useful for balance.

The vertebral column consists of 5 parts. The most cranial (uppermost) part is made up by the cervical vertebras (7), followed by thoracic (12), lumbar (5), sacral (4-5) and coccygeal vertebras (3-4).
A human is able to survive with just the axial portion of their skeleton.
Cervical vertebras make up the junction between the vertebral column and the cranium. Sacral and coccygeal vertebras are fused and thus often called "sacral bone" or "coccygeal bone" as unit.
The sacral bone makes up the junction between the vertebral column and the pelvic bones.


===Appendicular skeleton===
===Appendicular skeleton===
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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.
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.


==Function==
==Functions==
[[File:Human-Skeleton.jpg|thumb|right]]
[[File:Human-Skeleton.jpg|thumb|right|A human skeleton on exhibit at The Museum of Osteology, Oklahoma City, Oklahoma]]

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


===Support===
===Support===
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===Storage===
===Storage===
Bone matrix can store [[calcium]] and is involved in [[calcium metabolism]], and [[bone marrow]] can store [[iron]] in [[ferrotin]] and is involved in [[Human iron metabolism|iron metabolism]]. However, bones are not entirely made of calcium, but a mixture of [[chondroitin sulfate]] and [[Hydroxylapatite|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.
The [[Osteon|bone matrix]] can store [[calcium]] and is involved in [[calcium metabolism]], and [[bone marrow]] can store [[iron]] in [[ferrotin]] and is involved in [[Human iron metabolism|iron metabolism]]. However, bones are not entirely made of calcium, but a mixture of [[chondroitin sulfate]] and [[Hydroxylapatite|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.


===Endocrine regulation===
===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 the [[insulin]] secretion and sensitivity, in addition to boosting the number of [[beta cell|insulin-producing cells]] 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>
Bone cells release a hormone called [[osteocalcin]], which contributes to the regulation of [[blood sugar]] ([[glucose]]) and [[body fat|fat deposition]]. Osteocalcin increases both the [[insulin]] secretion and sensitivity, in addition to boosting the number of [[beta cell|insulin-producing cells]] 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>


==Gender differences==

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 [[Sexual dimorphism|sexually dimorphic]] as that of many other primate species, but subtle differences between sexes in the [[Morphology (biology)|morphology]] of the [[Human skull|skull]], [[dentition]], [[long bone]]s, and pelves (''sing.'' [[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.
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 [[Sexual dimorphism|sexually dimorphic]] as that of many other primate species, but subtle differences between sexes in the [[Morphology (biology)|morphology]] of the [[Human skull|skull]], [[dentition]], [[long bone]]s, and pelves (''sing.'' [[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.


===The skull===
===Skull===
A variety of gross morphological traits of the [[human skull]] demonstrate sexual dimorphism, such as the [[nuchal crest]], [[mastoid process]]es, [[supraorbital margin]], [[supraorbital ridge]], and [[Chin|mental eminence]].<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|coauthors=D.H. Ubelaker}}</ref>
A variety of gross morphological traits of the [[human skull]] demonstrate sexual dimorphism, such as the [[nuchal crest]], [[mastoid process]]es, [[supraorbital margin]], [[supraorbital ridge]], and [[Chin|mental eminence]].<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|coauthors=D.H. Ubelaker}}</ref>


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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 [[Morphometrics|morphometric]] or gross morphological analyses.
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 [[Morphometrics|morphometric]] or gross morphological analyses.


===The pelvis===
===Pelvis===
Human pelves exhibit 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>
Human pelves exhibit 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>


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==References==
==References==
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{{Library resources box
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|label=Skeletal system}}

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{{System and organs}}
{{System and organs}}
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