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Encyclopedia > Human skeleton
Front view of a skeleton of an adult human
Front view of a skeleton of an adult human
Back view of a skeleton of an adult human
Back view of a skeleton of an adult human

The human skeleton consists of both fused and individual bones supported and supplemented by ligaments, tendons, muscles and cartilage. It serves as a scaffold which supports organs, anchors muscles, and protects organs such as the brain, lungs and heart. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links Human_skeleton_back. ... Image File history File links Human_skeleton_back. ... This article is about the skeletal organs. ... In anatomy, the term ligament is used to denote three different types of structures:[1] Fibrous tissue that connects bones to other bones. ... For other uses, see Tendon (disambiguation). ... For other uses of Muscle, see Muscle (disambiguation). ... Cartilage is a type of dense connective tissue. ... A human brain. ... For the village in Tibet, see Lung, Tibet. ... The heart and lungs, from an older edition of Grays Anatomy. ...


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. The stapes or stirrup is the stirrup-shaped small bone or ossicle in the middle ear which attaches the incus to the fenestra ovalis, the oval window which is adjacent to the vestibule of the inner ear. ...


Fused bones include those of the pelvis and the cranium. Not all bones are interconnected directly: There are six bones 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. The pelvis (pl. ... Cranium can mean: The brain and surrounding skull, a part of the body. ... The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. ... The ossicles (also called auditory ossicles) are the three smallest bones in the human body. ... 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). ...

Contents

Development

Early in gestation, a fetus has a cartilaginous skeleton from which the long bones 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 clavicles 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 270 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 plates, 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. Gestation is the carrying of an embryo or fetus inside a female viviparous animal. ... For other uses, see Fetus (disambiguation). ... The long bones are those that are longer than they are wide, and grow primarily by elongation of the diaphysis, with an epiphysis at the ends of the growing bone. ... Section of fetal bone of cat. ... For other uses of Skull, see Skull (disambiguation). ... Collarbone and collar bone redirect here. ... Osteoblasts and osteoclasts on trabecula of lower jaw of calf embryo. ... Figure 3: Mandible of human embryo 24 mm. ... The cartilaginous bar of the mandibular arch is formed by what are known as Meckel’s cartilages (right and left) ; above this the incus is developed. ... For the record label, see Sacrum Torch. ... The coccyx is formed of up to five vertebrae. ... The vertebral column seen from the side Different regions (curvatures) of the vertebral column The vertebral column (backbone or spine) is a column of vertebrae situated in the dorsal aspect of the abdomen. ... Look up spine on Wiktionary, the free dictionary. ... The long bones are those that are longer than they are wide, and grow primarily by elongation of the diaphysis at an epiphysis at one end of the growing bone. ...


Segmental pattern

Much of the human skeleton maintains the ancient segmental pattern present in all vertebrates (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. For other uses, see Skeleton (disambiguation). ... This article does not cite any references or sources. ...


Organization

The human skeleton can be divided into the axial skeleton and the appendicular skeleton. diagram of the axial skeleton The axial skeleton consists of the 80 bones in the head and trunk of the human body. ... Appendicular skeleton diagram The appendicular skeleton, consisting of 126 bones, makes body movement possible and protects the organs of digestion, excretion, and reproduction. ...


Bones

See also: List of bones of the human skeleton

There are 206 bones in the matured adult human body, but this number can vary slightly from individual to individual.[1] A typical adult human skeleton consists of the following 206 bones depending on age, though this number does vary owing to a variety of anatomical variations; for example, a small portion of the human population have an extra rib, or an extra lumbar vertebra. ...


Function

The skeleton has six 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 vertebrates 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. This article does not cite any references or sources. ... Leverage redirects here. ...


Protection

The skeleton protects many vital organs: This article is about the biological unit. ...

For other uses of Skull, see Skull (disambiguation). ... A human brain. ... For other uses, see Eye (disambiguation). ... The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. ... Inner ear The inner ear is the bony labyrinth, a system of passages comprising two main functional parts: the organ of hearing, or cochlea and the vestibular apparatus, the organ of balance that consists of three semicircular canals and the vestibule. ... The vertebral column seen from the side Different regions (curvatures) of the vertebral column The vertebral column (backbone or spine) is a column of vertebrae situated in the dorsal aspect of the abdomen. ... The Spinal cord nested in the vertebral column. ... This article is about the bones called ribs. ... The sternum (from Greek στέρνον, sternon, chest) or breastbone is a long, flat bone located in the center of the thorax (chest). ... For the village in Tibet, see Lung, Tibet. ... The heart and lungs, from an older edition of Grays Anatomy. ... For transport in plants, see Vascular tissue. ... Collarbone and collar bone redirect here. ... Left scapula - front view () Left scapula - rear view () In anatomy, the scapula, or shoulder blade, is the bone that connects the humerus (arm bone) with the clavicle (collar bone). ... This article is about the body part. ... The ilium of the pelvis is divisible into two parts, the body and the ala; the separation is indicated on the internal surface by a curved line, the arcuate line, and on the external surface by the margin of the acetabulum. ... In anatomy, the hip is the bony projection of the femur which is known as the greater trochanter, and the overlying muscle and fat. ... For other uses, see Patella (disambiguation). ... The ulna (Elbow Bone) [Figs. ... For other uses, see Knee (disambiguation). ... Elbow redirects here. ... This article is about Carpal bones. ... FIG. 268– Bones of the right foot. ... For the municipality in Germany, see Wrist, Germany. ... For a review of anatomical terms, see Anatomical position and Anatomical terms of location. ...

Blood cell production

The skeleton is the site of haematopoiesis, which takes place in red bone marrow. Diagram that shows the development of different blood cells from hematopoietic stem cell to mature cells Haematopoiesis (from Ancient Greek: haima blood; poiesis to make) (or hematopoiesis in the United States; sometimes also haemopoiesis or hemopoiesis) is the formation of blood cellular components. ... For the Dir en grey album, see The Marrow of a Bone. ...


Storage

Bone matrix can store calcium and is involved in calcium metabolism, and bone marrow can store iron in ferritin and is involved in iron metabolism. For other uses, see Calcium (disambiguation). ... Calcium Calcium metabolism or calcium homeostasis is the mechanism by which the body maintains adequate calcium levels. ... For the Dir en grey album, see The Marrow of a Bone. ... Fe redirects here. ... Ferritin is a globular protein found mainly in the liver, which can store about 4500 iron (Fe3+)ions in a hollow protein shell made of 24 subunits. ... Human beings use 20 mg of iron each day for the production of new red blood cells, much of which is recycled from old red blood cells. ...


Endocrine regulation

Bone cells release a hormone called osteocalcin, which controls the regulation of blood sugar (glucose) and fat deposition. Osteocalcin increases both the secretion and sensitivity of insulin, in addition to boosting the number of insulin-producing cells and reducing stores of fat.[2] Osteocalcin is a protein found in bone and dentin; that plays a role in mineralization and calcium ion homeostasis ... In medicine, blood sugar is a term used to refer to levels of glucose in the blood. ... Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. ... In biochemistry, fat is a generic term for a class of lipids. ... Not to be confused with inulin. ... Beta cells are a type of cell in the pancreas in areas called the islets of Langerhans. ...


Sex-based differences

An articulated human skeleton, as used in biology education
An articulated human skeleton, as used in biology education

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. The shape of a female pelvis is flatter, more rounded and proportionally larger to allow the head of a fetus to pass. Men tend to have slightly thicker and longer limbs and digit bones (phalanges), while women tend to have narrower rib cages, smaller teeth, less angular mandibles, 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. Females also tend to have more rounded shoulder blades. Parturition redirects here. ... The phalanges in a human hand The name Phalanges is commonly given to the bones that form fingers and toes. ... This article is about the bones called ribs. ... The mandible (from Latin mandibÅ­la, jawbone) or inferior maxillary bone is, together with the maxilla, the largest and strongest bone of the face. ... The inion is the most prominent projection of the occipital bone at the lower rear part of the skull. ...


Disorders

See also: List of skeletal disorders

There are many disorders of the skeleton. One of the more prominent is osteoporosis. This is a list of skeletal disorders, these affect the development and structure of the skeletal system. ... Osteoporosis is a disease of bone that leads to an increased risk of fracture. ...


Osteoporosis

Main article: Osteoporosis

Osteoporosis is a disease of bone - leading to an increased risk of fracture. In osteoporosis, the bone mineral density (BMD) is reduced, bone microarchitecture is disrupted, and the amount and variety of non-collagenous proteins in bone is altered. Osteoporosis is defined by the World Health Organization (WHO) in women as a bone mineral density 2.5 standard deviations below peak bone mass (20-year-old sex-matched healthy person average) as measured by DXA; the term "established osteoporosis" includes the presence of a fragility fracture.[3] 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 diseases or as a result of smoking and medications, specifically glucocorticoids, when the disease is called steroid- or glucocorticoid-induced osteoporosis (SIOP or GIOP). Osteoporosis is a disease of bone that leads to an increased risk of fracture. ... This article is about the medical term. ... This article is about the skeletal organs. ... Internal and external views of an arm with a compound fracture, both before and after surgery A bone fracture is a medical condition in which a bone has cracked or broken. ... A bone mineral density (BMD) test, also called a bone mass measurement, is used to measure bone density and determine fracture risk for osteoporosis. ... Tropocollagen triple helix. ... WHO redirects here. ... In probability and statistics, the standard deviation of a probability distribution, random variable, or population or multiset of values is a measure of statistical dispersion of its values. ... A scanner used to measure bone density with dual energy X-ray absorptiometry. ... A fragility fracture is one that occurs as a result of a fall from standing height or less. ... The word menopause literally means the permanent physiological, or natural, cessation of menstrual cycles, from the Greek roots meno (month) and pausis (a pause, a cessation). ... In medicine, a chronic disease is a disease that is long-lasting or recurrent. ... The cigarette is the most common method of smoking tobacco. ... A medication is a drug or substance taken to reduce symptoms or cure an illness or medical condition. ... Glucocorticoids are a class of steroid hormones characterised by an ability to bind with the cortisol receptor and trigger similar effects. ...


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 also be prevented with having a good source of calcium and Vitmin D. Osteoporosis can be treated with bisphosphonates and various other medical treatments. In pharmacology, bisphosphonates (also called: diphosphonates) is a class of drugs that inhibits the resorption of bone. ...


Gallery

References

  1. ^ The Bones - The Human Body - BBC World Service
  2. ^ Lee, Na Kyung; et al. (August 2007). "Endocrine Regulation of Energy Metabolism by the Skeleton". Cell 130: 456-469. doi:10.1016. 
  3. ^ WHO (1994). "Assessment of fracture risk and its application to screening for postmenopausal osteoporosis. Report of a WHO Study Group". World Health Organization technical report series 843: 1–129. PMID 7941614. 

A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

See also

The lesser pelvis (or true pelvis) is that part of the pelvic cavity which is situated below and behind the pelvic brim. ... The lesser pelvis (or true pelvis) is that part of the pelvic cavity which is situated below and behind the pelvic brim. ... The pelvis is divided by an oblique plane passing through the prominence of the sacrum, the arcuate and pectineal lines, and the upper margin of the symphysis pubis, into the greater pelvis and the lesser pelvis. ... The lower circumference of the lesser pelvis is very irregular; the space enclosed by it is named the inferior aperture or outlet (apertura pelvis [minoris] inferior), and is bounded behind by the point of the coccyx, and laterally by the ischial tuberosities. ... The greater pelvis (or false pelvis) is the expanded portion of the cavity situated above and in front of the pelvic brim. ...

External links

  • A skeleton page for kids
  • Skeletal System & Bones of Human Body

  Results from FactBites:
 
Human skeleton - Wikipedia, the free encyclopedia (886 words)
The human skeleton is made of individual or joined bones (such as the skull), supported and supplemented by a structure of ligaments, tendons, muscles, cartilage and other organs.
The axial skeleton consists of bones in the midline and includes all the bones of the head and neck, the vertebrae, ribs and sternum.
The appendicular skeleton consists of the clavicles, scapulae, the arm bones, the bones of the pelvis and the leg bones.
  More results at FactBites »

 
 

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