View source for Human skeleton

[[Image:Human skeleton front_svg.png|thumb|250px|Front view of a skeleton of an adult human]]
[[Image:Human skeleton back_svg.png|thumb|250px|Back view of a skeleton of an adult human]]
{{SI}}
__NOTOC__
{{GS}}



==Overview==
The '''human skeleton''' consists of both fused and individual [[bone]]s supported and supplemented by [[ligament]]s, [[tendon]]s, [[muscle]]s and [[cartilage]]. It serves as a scaffold which supports organs, anchors muscles, and protects organs such as the [[human brain|brain]], [[lung]]s and [[heart]].

The longest and heaviest bone in the body is the [[femur]], and the smallest is the [[stapes]] bone in the middle ear. In an adult, the skeleton comprises around 20% of the total body weight.

Fused bones include those of the [[pelvis]] and the [[cranium]]. Not all bones are interconnected directly: There are 6 jnbones in the [[middle ear]] called the [[ossicles]] (three on each side) that articulate only with each other. The [[hyoid bone]], which is located in the neck and serves as the point of attachment for the [[tongue]], does not articulate with any other bones in the body, being supported by muscles and ligaments. 
Early in [[gestation]], a [[foetus]] has a cartilaginous skeleton from which the [[long bone]]s and most other bones gradually form throughout the remaining gestation period and for years after birth in a process called [[endochondral ossification]]. The flat bones of the [[skull]] and the [[clavicle]]s are formed from connective tissue in a process known as [[intramembranous ossification]], and [[ossification of the mandible]] occurs in the fibrous membrane covering the outer surfaces of [[Meckel's cartilages]]. At birth a newborn baby has approximately 300 bones, whereas on average an adult human has 206 bones (these numbers can vary slightly from individual to individual). The difference comes from a number of small bones that fuse together during growth, such as the [[sacrum]] and [[coccyx]] of the [[vertebral column]]. The sacrum (the bone at the base of the [[spine]]) consists of five bones which are separate at birth but fuse together into a solid structure in later years. An infant is born with zones of cartilage, called [[epiphyseal plate]]s, between segments of bone to allow further growth. Growing is usually completed between ages 13 and 18, at which time the epiphyseal plates of long bones close allowing no further growth.

==Segmental pattern==
Much of the human [[skeleton]] maintains the ancient segmental pattern present in all [[vertebrate]]s (mammals, birds, fishes, reptiles and amphibians) with basic units being repeated. This segmental pattern is particularly evident in the vertebral column and in the ribcage.

==Function==
The skeleton has five main functions: 

===Support===
The skeleton provides the framework which supports the body, and maintains its shape. The joints between bones permit 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===
Movement in [[vertebrate]]s is powered by skeletal muscles, which are attached to the skeleton by tendons. Without the skeleton to give leverage, movement would be greatly restricted. However, biologically speaking, the skeleton does not enable movement.

===Protection===
The skeleton protects many vital [[organ (anatomy)|organ]]s:
* The [[skull]] protects the [[human brain|brain]], the [[eye]]s, and the [[middle ear|middle]] and [[inner ear]]s.
* The [[vertebral column|spine]] protects the [[spinal cord]].
* The [[rib cage]], spine, and [[sternum]] protect the [[lung]]s, [[heart]] and major [[circulatory system|blood vessels]].
* The [[clavicle]] and [[scapula]] protect the [[shoulder]].
* The [[ilium (bone)|ilium]] and spine protect the digestive and urogenital systems and the [[hip (anatomy)|hip]].
* The [[patella]] and the [[ulna]] protect the [[knee]] and the [[elbow-joint|elbow]] respectively.
* The [[carpus|carpals]] and [[tarsus (skeleton)|tarsals]] protect the [[wrist]] and [[ankle]] respectively.

===Blood cell production===
The skeleton is the site of [[haematopoiesis]] – the generation of [[blood cell]]s, which takes place in red [[bone marrow]].

===Storage===
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]].

==Organization==
The human skeleton can be divided into the [[axial skeleton]] and the [[appendicular skeleton]].

==Bones==
{{Seealso|List of bones of the human skeleton}}
There are more than 200<ref>[http://www.bbc.co.uk/worldservice/sci_tech/features/health/thehumanbody/bones1.shtml The Bones - The Human Body - BBC World Service]</ref> bones in the human body.

==Gender differences==

There are many differences between the male and female human skeletons. Most prominent is the difference in the pelvis, owing to characteristics required for the processes of [[childbirth|parturition]] (childbirth). The shape of a female pelvis is flatter, more rounded and proportionally larger to allow the head of the fetus to pass. Men tend to have slightly thicker and longer limbs and digit bones ([[phalanges]]), while women tend to have narrower [[rib cage]]s, smaller teeth, less angular [[mandible]]s, less pronounced cranial features such as the brow ridges and [[external occipital protuberance]] (the small bump at the back of the skull), and the carrying angle of the forearm is more pronounced in females.

<gallery>
Image:Skeleton2.jpg|An articulated human skeleton, as used in biology education
</gallery>

==Disorders==
{{Seealso|List of skeletal disorders}}
There are many disorders of the skeleton. One of the more prominent is [[osteoporosis]].

===Osteoporosis===
{{Main|Osteoporosis}}
Osteoporosis is a [[disease]] of [[bone]] - leading to an increased risk of [[bone fracture|fracture]]. In osteoporosis, the [[bone mineral density]] (BMD) is reduced, bone microarchitecture is disrupted, and the amount and variety of non-[[collagen]]ous proteins in bone is altered. Osteoporosis is defined by the [[World Health Organization]] (WHO) in women as a bone mineral density 2.5 [[standard deviation]]s below peak bone mass (20-year-old sex-matched healthy person average) as measured by [[Dual energy X-ray absorptiometry|DXA]]; the term "established osteoporosis" includes 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 |issue= |pages=1–129 |year=1994 |pmid=7941614 |doi=}}</ref> Osteoporosis is most common in women after the [[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 [[medications]], specifically [[glucocorticoid]]s, when the disease is called '''steroid-''' or '''glucocorticoid-induced osteoporosis''' (SIOP or GIOP).
 
Osteoporosis can be prevented with lifestyle advice and medication, and preventing falls in people with known or suspected osteoporosis is an established way to prevent fractures. Osteoporosis can be treated with [[bisphosphonate]]s and various other medical treatments.

==External links==
*[http://yucky.kids.discovery.com/noflash/body/pg000124.html A skeleton page for kids]
*[http://www.syvum.com/cgi/online/serve.cgi/squizzes/biology/human_skeleton_1.html Skeletal System & Bones of Human Body]

==Gallery==
<gallery>
Image:Skeleton woman back.jpg|Drawing of the reverse of a female skeleton giving an impression of the location relative to surface markings
Image:SkeletonBodyFront.gif|A medical drawing by a German physician from 1910
Image:Skelett-Mensch-drawing.jpg|Annotated skeleton
</gallery>

==References==

{{Reflist}}

{{Bonesofskeleton}}
{{Facial bones}}
{{Cranium}}
{{Sutures}}
{{Bones of upper extremity}}
{{Spine}}
{{Bones of lower extremity}}
{{Pelvis}}
{{HumanBones}}
{{Hormones}}



[[Category:Human anatomy|Skeleton]]
[[Category:Skeletal system]]
[[Category:Endocrine system]]
[[Category:Endocrinology]]


[[ar:هيكل عظمي بشري]]
[[bs:Kostur čovjeka]]
[[cs:Kostra (člověk)]]
[[es:Esqueleto humano]]
[[fa:استخوان‌بندی انسان]]
[[fr:Squelette humain]]
[[ko:인체골격]]
[[is:Beinagrind mannsins]]
[[it:Scheletro (anatomia umana)]]
[[he:מערכת השלד]]
[[ku:Kakut]]
[[lv:Cilvēka skelets]]
[[ms:Rangka manusia]]
[[pl:Układ kostny człowieka]]
[[pt:Esqueleto humano]]
[[sk:Kostra človeka]]
[[sl:Okostje človeka]]
[[tl:Kalansay ng tao]]
[[th:โครงกระดูกมนุษย์]]
[[ur:ڈھانچہ انسانی]]
[[zh:人體骨架]]


{{WH}}
{{WS}}